Interventional Radiology

Question 1

Femoral arterial access technique

Answer 1

The common femoral artery begins inferior to the inguinal ligament. From lateral to medial, the mnemonic NAVL helps to localize the femoral nerve, artery, vein, and lymphatics.

The ideal position to acces the femoral artery is the inferomedial margin of the femoral head, for two reasons. First, the femoral head provides a hard surface to press against to provide adequate hemostasis. Second, at the level of the femoral head, the femoral artery and nerve are side by side. If arterial puncture is performed too low, the femoral vein may be traversed with possible formation of arteriovenous fistula.

Question 2

Hematoma

Answer 2

A hematoma may be superficial or retroperitoneal. A superficial subcutaenous hematoma has a generally benign clinical course, while a retroperitoneal hematoma carries a risk of fatal hemorrhage.

There is increased risk of retroperitoneal hematoma with a high (more cranial) arterial puncture above the pelvic brim.

Question 3

Pseudoaneurysm

Answer 3

Pseudoaneurysm formation occurs in approximately 1% of arterial punctures. On color Doppler, a pseudoaneurysm appears as a swirling yin-yang with high-velocity flow at the site of communication with the femoral artery.

Watchful waiting can be performed for a small pseudoaneurysm <1 cm in size. Ultrasound-guided thrombin injection is the treatment of choice for a pseudoaneurysm >1 cm. Less commonly, ultrasound-guided compression of the neck of the pseudoaneurysm can be performed to thrombose the pseudoaneurysm.

Question 4

Arteriovenous fistula (AVF)

Answer 4

An arteriovenous fistula (AVF) is an anomalous connection between an artery and a vein. AVFs are usually asymptomatic but may enlarge and ultimately cause high-output cardiac failure.

There is increased risk of developing an iatrogenic AVF with a low (inferior/distal) femoral arterial puncture. The femoral vein often passes deep to (instead of medial to) the femoral artery distal to the standard puncture site.

On Doppler ultrasound, an AVF demonstrates arterial flow within a vein and there is loss of normal triphasic waveform in the artery. Increased diastolic flow is often seen in the artery proximal to the fistula.

Question 5

Air embolism

Answer 5

Air embolism is a rare but potentially life-threatening complication of vascular procedures.

The most dangerious portion of a venous access procedure is the insertion of the catheter into the peel-away sheath.

If air embolism is suspected (e.g., if the patient becomes acutely hypoxic as the catheter is inserted intot he peel-away sheath), the patient should be immediately placed in the left lateral decubitus (left side down) so that the air bubble remains antidependent in the right heart. 100% oxygen should be administered. If practial, fluoroscopy can be used to identify the air bubble. Catheter aspiration can be considered if the air bubble is large.

Question 6

Injection rates

Answer 6

The terminology for injection rates for angiographic runs is “cc/sec for total cc”. For instance “25 for 50” means an injection rate of 25 cc/sec for a total of 50 cc.

The diameter in mm of a vessel is a rough guide to the injection rate (in cc/sec), and the total volume of cotnrast injection depends on the intravascular volume of the vascular bed.

Aortogram (aortic arch): 20 for 30.

Abdominal aorta: 20 for 20.

Inferior vena cavogram: 20 for 30.

Mesenteric artery 5 for 25.

Renal artery 5 for 15.

Distal artery: 3 for 12.

Question 7

Percutaneous transluminal angioplasty (PTA)

Answer 7

Percutaneous transluminal angioplasty (PTA) is the first-line technique for treatment of a stenosis, where a balloon is inflated across the stenosis to create a controlled stretch injury adn increase the luminal cross-sectional area.

When treating a stenosis caused by atherosclerotic plaque, angioplasty widens the luminal diameter due to disruption of the intima and extension of the plaque into the media.

Most balloons are non-compliant. That is, they have a fixed diameter that does not expand no matter the air pressure. If a non-compliant balloon is inflated above its rated maximum pressure, the balloon will burst.

In general, a balloon should be selected that is 10-20% larger than the vessel diameter.

Balloons are sized by diameter in millimeters and lenght in centimeters. For instance a 10 x 6 balloon is 10 mm in diameter and 6 cm in length.

Risks of angioplasty include distal emboli, vessel rupture, and dissection. Anticoagulation (typically heparin) should always be used with angioplasty.

Question 8

Stents

Answer 8

The two broad categories of stents are balloon-expandable and self-expandable stents.

In general, balloon-expandable stents have a higher radial force upon deployment but will not rebound if crushed. Thus, balloon-expandable stents are suboptimal for sites prone to external compression, such as around joints or the adductor canal in the leg.

Self-expandable stents are more flexible and trackable through the vessels than balloon-expandable stents. Their use is favored when the route to the lesion is tortuous or when the anatomy is prone to external compression.

In general, a stent should be selected that is 1-2 cm longer than the stenosis, with a diameter that is 1-2 mm wider than the unstenosed vessel lumen. A rule of thumb is 10% oversizing of an arterial stent and 20% oversizing of a venous stent.

Most stents are fenestrated and provide only a scaffolding-like support; however, covered stents are employed for treatment of pseudoaneurysm, dissection, and TIPS.

Question 9

Embolic materials

Answer 9

The two main categories of embolic materials are premanent (coils, particles, glue, and sclerosing agent) and temporary (absorbable gelatin sponge and autologous clot).

Coils create thrombosis by inducing vascular stasis. The main advantage of coils is the ability for precise and quick placement, without distal embolization. The primary disadvantage is sacrifice of distal access: Once a vessel is coiled, it cannot be re-accessed for retreatment. When using coils for embolization of a specific lesion, the general technique is to first coil distal to the lesion, the proximal to it. This prevents recurrent bleeding from retrograde collaterals.

Particles flow distally to occlude the small capillaries. Two types of particles are trisacyl gelatin microspheres (Embospheres, BioSphere Medical) and polyvinyl alcohol.

Adsorbable gelatin sponge (Gelfoam, Pfizer) is the most commonly used temporary embolic agent, lasting 2-6 weeks. Of important note, because Gelfoam is dissolved foam, post-procedural CT imaging can show numerous gas locules in the embolized organ. This appearance can mimic abscess and careful clinical observation is necessary to prevent unnecessary interventions.

Sodium tetradecyl sulfate is a sclerosing agent used for vascular malformations adn varices.

Cyanoacrylate is a special glue that rapidly hardens when it comes in contact with blood.

Question 10

Complications of embolization

Answer 10

Post-embolization syndrome usually occurs within the first day after embolization and clinically presents with pain, cramping, fever, and nausea/vomiting, thought to be due to release of endovascular inflammatory modulators by infarcted tissue. Treatment is NSAIDS, opoids when appropriate, and IV fluids.

Non-target embolization is unintentional embolization of structures other than the target. For instance, during uterine fibroid embolization there is a risk of non-target embolization of the ovaries. During bronchial artery embolization, there is a risk of non-target embolization to the brain causing stroke and to the spinal arteries causing paralysis.

Question 11

Catheter sizing

Answer 11

Catheters are sized in French (Fr), where 1 Fr = 0.33 mm. For instance, a 6 Fr catheter has an external diameter of 2 mm. The luminal diamter will be slightly smaller.

Sheath versus catheter: A sheath has a defined luminal diameter; however, the overall diameter of the catheter will be slightly larger. For instance, a 6 Fr sheath can by definition fit a 6 Fr catheter inside, but will be a 7 or 8 Fr in external diameter

Question 12

High-flow catheters

Answer 12

High-flow (also known as flush) catheters have multiple sideholes and may be coiled (most commonly; known as pigtail/omniflush catheter), curved, or straight.

High-flow catheters are used for large vessel angiography, such as the aorta adn vena cava.

Question 13

Selective and superselective catheters

Answer 13

Selective and superselective catheters have a single hole at the end of the catheter. There are numerous shapes of the distal portion, each tailored towards a specific situation or general purpose use.

C2 and SOS are reverse curved-tip catheters; and Berenstein is an angled-tip catheter.

Question 14

Wires

Answer 14

Wires are sized in inches, with a standard wire measuring 0.035” in diameter and a microwire measuring 0.018” in diameter.

Standard wires have a floppy tip or J-tip, which allows the wire to be safely inserted blindly (although once in teh vesself the course should be followed on fluoroscopy).

A Bentson wire is a typical floppy tip wire; Rosen is a J-tip wire.

Hydrophilic wires are used to cross a stenosis or for initial cannulation of an indwelling device, as would be performed for a routine check and change.

Roadrunner (Cook) and Glidewire (Terumo) wires are hydrophilic.

Stiff wires are used when structural rigidity is required. For instance, a devices that dilates the subcutaneous tissues (such as a sheath, biliary drain, nephrostomy tube, etc.) needs to be inserted over a stiff wire.

An Amplatz (Boston Scientific) wire is a commonly used superstiff wire.

Question 15

Giant cell arteritis

Answer 15

Giant cell arteritis (GCA) is a medium and large-vessel vasculitis that has overlapping imaging findings with Takayasu arteritis. GCA tends to affect older patietns (typically greater than 50 years of age) compared to Takayasu arteritis.

The medium-sized upper extremity arteries are most commonly affected in GCA, including the subclavian, axillary, and brachial arteries. The aorta is rarely involved, unlike in Takayasu arteritis. GCA typically produces long smooth stenoses and occlusions.

Definitive diagnosis is with temporal artery biopsy. Treatment is steroids.

Question 16

Congenital anomalies of the superior vena cava (SVC)

Answer 16

Normally, the embyrologic left anterior cardinal vein regresses and the right anterior cardinal vein develops into the SVC.

Left-sided SVC is due to persistence of the embryological left anterior cardinal vein and regression of the right anterior cardinal vein. The left SVC usually drains directly into the coronary sinus -> right atrium. Rarely, the left SVC drains directly into the left atrium causing a left to right shunt. Left-sided SVC is weakly associated with congenital heart disease (CHD). Left SVC is an incidental finding in 0.5% of the population but is seen in 4% of patients with CHD.

A duplicated SVC is due to persistance of both the right and left anterior cardinal veins.

Question 17

SVC obstruction

Answer 17

Acute obstruction of the SVC causes SVC syndrome, which clinically presents as facial and upper extremity edema and cyanosis. Acute SVC syndrome is a vascular emergency.

In contrast to acute SVC syndrome, chronimc occlusion or stenosis of the SVC may be asymptomatic. If symptoms are present, facial edema that improves with standing is characteristic.

The most common causes of SVC obstruction are compression by thoracic malignancy, cathether-associated thrombosis, and mediastinal fibrosis after histoplasmosis exposure.

A classic cross-sectional abdominal imaging finding in SVC obstruction is increased enhancement of hepatic segment IVa due to collateral opacification of the vein of Sappey. The vein of Sappey drains the liver in the region of the falciform ligament and communicate with internal thoracic veins, which act as collateral vessels in the setting of SVC occlusion.

Combined internal jugular and femoral approaches may be necessary for treatment of SVC occlusion. Stenting is often necessary.

Question 18

Pulmonary artery angiography technique

Answer 18

Before performing a pulmonary angiogram, it is essential to evaluate an EKG to ensure that a left bundle branch block (LBBB) is not present. If the pulmonary artery catheter were to cause temporary right bundle branch block in the presence of a LBBB, the lack of left-sided conduction may cause complete heart block, which can be fatal. A temporary pacer should be placed prior to pulmonary arteriography in the presence of a LBBB.

Normal right-sided pressures: Right atrium: 0-8 mm Hg. Right ventricle: 0-8 mm Hg diastolic; 15-30 mm Hg systolic. Pulmonary artery: 3-12 mm Hg diastolic; 15-30 mm Hg systolic.

Question 19

Pulmonary arteriovenous malformation (AVN)

Answer 19

A pumonary arteriovenous malformation (AVM) is an abnormal connection between the pulmonary artery and pulmonary veins, causing a right to left shunt.

Patients with hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, may have multiple pulmonary AVMs. HHT can clinically present with brain abscess, stroke, or recurrent epistaxis (due to nasal mucosa telangiectasia).

Coils must be used to embolize a pulmonary AVM. Particles are contraindicated as teh right to left shunt would cause brain emboli and infarction.

Most pulmonary AVMs have a single feeding artery and coiling of this inflow artery (via a pulmonary arterial approach) is usually sufficient treatment. Note that the treamtent of peripheral (e.g. in a limb) AVM generally requires elimination of the entire nidus, which is often fed from multiple arterial branches.

An asymptomatic lesion with a feeding artery size >3 mm or a symptomatic lesion (i.e., prior infarct or brain abscess) is an indication for treatment.

Question 20

Bronchial artery embolization for hemoptysis

Answer 20

Massive hemoptysis (hemoptysis of >300 mL/24 h) has a very high mortality, most commonly due to asphyxiation. The vast majority (90%) of cases of hemoptysis involve the bronchial arteries, with the pulmonary arterial circuluation, the subclavian, internal mammary, inferior phrenic, and celiac arteries may be involved, so if a patient continues to bleed after evaluation of the bronchial and pulmonary arterial circulation, the subclavian, internal mammary, inferior phrenic, and celiac arteries should be evaluated as well.

Chronic inflammation can lead to hypertrophied bronchial arteries and subsequent hemoptysis. In the USA, cystic fibrosis and thoracic malignancy are the most common causes of hemoptysis. Worldwide, tuberculosis and fungal infection are more common.

The bronchial artereis arise from the thoracic aorta at T5-T6, although the arterial anatomy is quite variable. There are usually one or two bronchial arteries on each side.

Embolization is performed with a distal embolic agent, most commonly particles. Initial angiography should carefully evaluate for the rare presence of a left to right shunt prior to particle embolization to prevent inadvertent cerebral embolization. Embolization is usually performed to near-stasis. Because rebleeding after treatment is common, coils are rarely used to treat hemoptysis. Because coils prevent repeat access, the use of coils would preclude retreatment.

A potentially devastating complication is nontarget embolization of the spinal cord via the anterior spinal artery or smaller tributaries arising from bronchial and intercostal arteries. A complete neurological exam should be documented prior to the procedure.

Question 21

Osseous landmarks for abdominal and pelvic angiography

Answer 21

Celiac artery: Arises from the aorta at the level of T12 vertebral body.

Superior mesenteric artery (SMA): Arises at the level of the T12-L1 disk space.

Renal arteries: Arise at the level of the L1-L2 disk space.

Inferior mesenteric artery (IMA): Arises to the left of the midline at the L2-L3 disk space.

Question 22

Celiac axis anatomy

Answer 22

The anatomy of the celiac axis and abdominal viscera is highly variable.

Approximately 75% of the time the celiac artery demonstrates normal arterial anatomy with three main branches: The left gastric, the common hepatic, and the splenic artery.

The left gastric artery may be the source of bleedin in esophageal Mallory-Weiss tear.

The left gastroepiploic artery arises from the splenic artery and anastomoses with the right gastroepiploic artery along the greater curvature of the stomach. The right gastroepiploic artery arises from the gastroduodenal artery.

Question 23

Hepatic arterial anatomy and variants

Answer 23

Most commonly (75%), the proper hepatic artery supplies blood to the liver. The proper hepatic artery is the continuation of the common hepatic artery after the takeoff of the gastroduodenal artery. The proper hepatic artery divides into the right and left hepatic artereis. The cystic artery arises from the right hepatic artery to supply the gallbladder.

A replaced right hepatic artery (RRHA) is present in 10-18% of patients, where the right hepatic artery arises from the SMA. An RRHA may become clinically significant in the setting of SMA disease or during abdominal surgery.

An accessory right hepatic artery is an artery arising from the SMA that supplies the right hepatic lobe in the presence of a normal right hepatic artery (arising from the proper hepatic artery).

A replaced left hepatic artery (RLHA) is present in 11-12% of patients, where the left hepatic artery arises form the left gastric artery.

An accessory left hepatic artery is an artery arising from the left gastric artery that supplies the left hepatic lobe in the presence of a normal left hepatic artery (arising from the proper hepatic artery).

Question 24

Superior mesenteric artery (SMA)

Answer 24

The superior mesenteric aretery (SMA) arises from the anterior aorta at about the level of T12-L1 to supply the distal duodenum, the entire small bowel, and the proximal large bowel from the cecum to the mid-transverse colon.

The inferior pancreaticoduodenal artery is the first branch of the SMA. The inferior pancreaticoduodenal artery forms collaterals with the celiac artery.

The middle colic artery arises from the SMA and supplies the transverse colon. The middle colic artery anastomoses with the marginal artery of Drummond.

The right colic artery courses retroperitoneally, where it supplies the right colon and hepatic flexure.

The terminal artery of the SMA is the ileocolic artery, which sends arterial branches to the terminal ileum, cecum, and appendix.

Question 25

Inferior mesenteric artery (IMA)

Answer 25

The inferior mesenteric artery (IMA) originates at the left anterior aspect of the aorta at L3-L4. The IMA gives off the left colic artery to supply the descending colon. The sigmoid arteries are variable in number. They run in the sigmoid mesocolon to supply the sigmoid. The IMA terminates as the superior rectal (hemorrhoidal) artery, which supplies the upper rectum.

Question 26

Internal Iliac branches

Answer 26

The anterior division of the internal iliac artery supplies most of the pelvic viscera. The branches of the anterior division include the inferior/middle rectal artery (anastomoses with the IMA via the pathway of Winslow), the uterine artery, the obturator artery, adn the inferior gluteal artery. The posterior division of the internal iliac artery supplies the musculature of the pelvic and gluteal regions. The branches of the posterior division include the lateral sacral artery, the iliolumbar artery (anastomoses with external iliac via the deep circumflex iliac artery), and the superior gluteal artery.

Question 27

External iliac branches

Answer 27

The inferior epigastric artery anastomoses with the superior epigastric artery. The deep circumflex iliac artery anastomoses with the internal iliac via the iliiolumbar artery. The femoral artery continues distally to supply the leg.

Question 28

Abdominal artery anastomoses

Answer 28

The arc of Buhler is an uncommon short-segment direct connection between the celiac artery and the SMA. It is a persistent embryologic remnant and not an acquired collateral pathway. The inferior pancreaticoduodenal artery is the first SMA branch. It forms a rich collateral network with the celiac about the pancreatic head, called the pancreatic cascade. The arc of Barkow connects the SMA to the celiac axis via the right and left epiploic arteries. The marginal artery of Drummond is the major SMA IMA anastomosis. It lies in the peripheral mesentery of the colon, adjacent to the mesenteric surface of the colon. The marginal artery of Drummond is comprised of branches from the ileocolic, right, middle, and left colic arteries. Normally, the marginal artery of Drummond is small in caliber, but it may become prominent in the setting of IMA or SMA disease. The arc of Riolan is an inconstant SMA IMA anastomosis. The arc of Riolan also runs through the colonic mesentery, but more medial compared to the marginal artery of Drummond. The Cannon-Bohm point is the point of transitional blood supply to the colon between the SMA (proximal) and IMA (distal), at the splenic flexure. This watershed zone is susceptible to ischemia in case of systemic arterial insufficiency. External iliac thoracic aorta: The inferior epigastric artery arises from the external iliac artery and anastomoses with the thoracic aorta via the internal mammary artery. External iliac internal iliac: The deep circumflex iliac artery arises from the external iliac artery and anastomoses with the posterior division of the internal iliac artery via the iliolumbar artery. Internal iliac IMA: the inferior/middle rectal arteries arise from the internal iliac artery and anastomose with the IMA via the superior rectal artery. This collateral pathway is the path of Winslow (rectal arcade).

Question 29

Polyarteritis nodosa (PAN)

Answer 29

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis of small and medium-sized arteries that causes multiple small visceral aneurysms. P-ANCA is usually elevated. The differential diagnosis of multiple renal artery aneurysms includes multiple septic emboli, speed kidney (due to chornic methamphetamine abuse), and Ehlers-Danlos. PAN typically affects renal, hepatic, and mesenteric end-arterioles. PAN is associated with several medical conditions remembered with the mnemonic CLASH (cryoglobulinemia, leukemia, rheumatoid arthritis, Sjogren syndrome, and hepatitis B). Treatment of PAN is with steroids, not procedures.

Question 30

Splenic artery aneurysm

Answer 30

Splenic artery aneurysm is teh most common visceral aneurysm. Multiparous females and patients with portal hypertension are at increased risk of developing splenic artery aneurysms. Splenic artery aneurysms have an increase risk of rupture during pregnancy. A splenic artery pseudoaneurysm may be the result of trauma or pancreatitis. Indications for treatment of a splenic artery aneurysm include presence of symptoms (such as left upper quadrant pain), aneursym size \>2.5 cm, and prior to expected pregnancy. Endovascular coil embolization is the preferred approach. Coils are first placed distal to the aneurysm neck (to exclude retrograde collateral flow), then placed proximally.

Question 31

Hepatic artery aneursym

Answer 31

Hepatic artery aneursym is the second most common visceral aneurysm. Embolization of the right hepatic artery distal to the cystic artery (which arises from the right hepatic artery) is preferred, as embolization proximal to teh cystic artery increases the risk of ischemic cholecystitis, which may be seen in up to 10% of cases.

Question 32

Cirrhosis

Answer 32

The classic angiographic finding of liver cirrhosis is corkscrewing of the hepatic artery branches, caused by liver fibrosis. A hypervascular mass in a cirrhotic liver may represent hepatocellular carcinoma.

Question 33

Mesenteric ischemia overview

Answer 33

Mesenteric ischemia is inadequate blood supply to the bowel. It is seen most commonly in the elderly and has multiple causes, including acute arterial embolism, chronic arterial stenosis, venous occlusion, and low-flow states. For the purposes of interventions, the etiologies can be divided into acute or chronic.

Question 34

Acute mesenteric ischemia

Answer 34

Acute mesenteric ischemia typically presents as catastrophic abdominal pain, often with lactic acidosis. Acute mesenteric ischemia is most commonly caused by SMA embolus. An SMA embolism distal to the middle colic artery carries the highest risk of intestinal ischemia, as there are few native distal collaterals. The middle colic artery anastomoses with the IMA via the marginal artery of Drummond and the arc of Riolan. In most patients with acute mesenteric ischemia, treatment is surgical revascularization (embolectomy or bypass), direct inspection of bowel, and resection of necrotic bowel. In select patients with acute embolic mesenteric ischemia (patients without peritoneal signs or clinical findings suggestive of bowel necrosis), endovascular therapy with thrombolysis or suction embolectomy may be performed. Nonocclusive mesenteric ischemia (NOMI) is a highly lethal (70-100% mortality) form of acute mesenteric ischemia. NOMI is also known as "intestinal necrosis with a patent arterial tree" and features spasm and narrowing of multiple branches of the mesenteric arteries. Direct arterial infusion of the vasodilator papaverine (60 mg bolus, then 30-60 mg/h) is the treatment of NOMI.

Question 35

Chronic mesenteric ischemia

Answer 35

Chronic mesenteric ischemia is usually caused by atherosclerosis. The classic clinical presentation is postprandial abdominal pain out of proportion to the physical exam. Mesenteric angiography shows ostial narrowing of the mesenteric vessels, often with post-stenotic dilation. The lateral aortogram is the most useful view to evaluate the origins of the celiac and superior mesenteric arteries. Because mesenteric collaterals are so extensive, at least two of three mesenteric arteries (celiac, SMA, and IMA) must be diseased to produce symptoms in chronic disease. Chronic mesenteric ischemia can be treated endovascularly with angioplasty and stenting.

Question 36

Role of interventional radiology in gastrointestinal (GI) bleeding

Answer 36

Gastrointestinal (GI) bleeding can be classifed as upper GI (bleeding source proximal to the ligament of Treitz), lower GI (bleeding source distal to the ligament of Treitz), and variceal. Variceal bleeding is due to portal hypertension and is treated by reducing portal pressure. Endoscopy is the best initial procedure for acute upper GI bleeding. Endoscopy can be both diagnostic and therapeutic. For lower GI bleeding, a hemodynamically stable patient should first be evaluated by mesenteric CT angiogram or nuclear medicine tagged red blood cell scan to localize the bleed, as these tests are thought to be more sensitive than angiography. A bleeding rate of 0.5 to 1.0 mL/min is generally required to be angiographically positive. A tagged red blood cell scan cand detect bleeding rate as low as 0.2 to 0.4 mL/min. Many institutions now favor mesenteric CT angiography as the first test for evaluation of acute lower GI bleeding because CT is rapid, easy to perform, and readily available. On CTA, acute bleeding is seen as contrast extravasatio. CTA may be able to detect bleeding rates as low as 0.35 mL/min. A hemodynamically unstable patient with clinical evidence of current GI bleeding may go straight to angiography. Due to the copious collaterals between the celiac axis and the SMA, it is often reasonalbe to perform empirical (in absence of visualized extravasation) embolizations of the left gastric artery in upper GI bleeding. However, lower GI collaterals are much less well developed and there is a significant risk of bowel infarct with indiscriminate lower GI embolization. Intraarterial infusion of vasopressin (antidiuretic hormone) can often control active lower GI bleeding, but there is very high rebleeding rate once the infusion is stopped. Vasopressin is most useful in cases of bleeding from antimesenteric vessels, which are more difficult to reach directly by catheter. Major complications of vasopressin are seen in up to 20% including arrhythmia, pulmonary edema, and hypertension. Vasopressin is directly infused into the SMA or IMA. The dose of vasopressin is 0.2-0.4 units per minute (100 units mixed in 500 mL saline given at 1 mL/minute), given as a continous infusion for up to 24 hours. Vasopressin can only be used for 24 hours before tachyphylaxis (lack of further response) develops.

Question 37

Angiodysplasia

Answer 37

Angiodysplasia is an acquired vascular anomaly that is a common cause of chronic intermittent lower GI bleeding, most typically located in the right colon or cecum. Because angiodsyplasia is so prevalent (identified in up to 15% of patients incidentally), the presence of angiodsyplasia is so prevalent (identified in up to 15% of patients incidentally), the presence of angiodysplasia in a bleeding patient should not stop the hunt for other possible sources. Even when angiodysplasia is the cause of bleeding, active extravasation is rarely seen. On imaging, angiodysplasia is a tangle of vessels with early filling of an antimesenteric draining vein. The typical tram-track appearance is caused by simultaneous opacification of the parallel artery and vein. Endovascular treatments, such as vasopressin or embolization, are generally not effective due to the abnoral vessels of angiodysplasia. Treatment is endoscopy with electrocoagulation, laser therapy, or other techniques. Surgery can be performed for recurrent or uncontrollabel bleeding, but is usually not necessary.

Question 38

Diverticular bleed

Answer 38

Diverticulosis is the most common cause of lower GI bleeding in older adults. Most patients respond to conservative management, but angiography can be used for stable or unstable patients who fail medical management. If active extravasation is seen, potential therapies include superselective embolization (most commonly with coils) or vasopressin infusion.

Question 39

Atherosclerotic renal artery stenosis

Answer 39

Atherosclerosis is most common cause of renal artery stenosis in older adults. Atherosclerosis tends to affect the ostia (origin) of the renal arteries. Angioplasty and stenting have greater long-term patency compared to angioplasty alone. The overall clinical benefit of endovascular revascularization is controversial. In 2009, the ASTRAL tiral published in the New England Journal of Medicine compared medical therapy alone to medical therapy and endovascular renal artery revascularization. This study found no benefit of endovascular treatment with respect to blood pressure, renal function, or mortality. The criticisms of the ASTRAL trial are that there was a lack of seere lesions in the patient population and the patients receiving medical treatment did better than in previous studies.

Question 40

Fibromuscular dysplasia (FMD)

Answer 40

Fibromuscular dysplasia (FMD) is an idiopathic vascular disease affecting primarily the renal and carotid arteries. FMD is bilateral two thirds of the time. FMD is predominantly seen in young or middle-aged women. In contrast to the ostial involvement of renal artery atherosclerosis, FMD tends to affect the mid or distal third of the renal arteries. The most common form of FMD is the medial fibroplasia subtype (80%), which features the classic string of pearls or stign of beads appearance on agiography. A less common form is intimal fibroplasia, which is more common in children and appears as a smooth stenosis, not the string of pearls typical of medial fibroplasia. Perimedial and adventitial fibroplasia are less common variants. FMD clinically responds well to angioplasty alone, with improved blood pressure control in 97%, including a 42% cure rate and a 90% patency rate at 5 years. The high clinical success rate is thought to be due to mechanical disruption of the fibrous tissue by the angioplasty balloon. Restenosis following angioplasty occurs relatively frequently, in 10-15% of patients. Stenting of FMD is not recommended, as stenting can complicate retreatent with angioplasty and lead to in-stent stenosis due to intimal hyperplasia.

Question 41

Neurofibromatosis

Answer 41

Neurofibromatosis may cause renal artery stenosis in children.

Question 42

Renal cell carcinoma (RCC)

Answer 42

Most renal cell carcinomas (RCC) are hypervascular. The tumors often feature arteriovenous shunting and venous lakes, with a classic angiographic appearance of bizarre neovascularity.

Question 43

Oncocytoma

Answer 43

Oncocytoma is a benign renal mass that cannot be reliably distinguished from renal cell carcinoma on cross-sectional imaging. Angiography classically shows a spokewheel appearance with a peritumoral halo. In contrast to RCC, bizarre neoplastic vessels are absent.

Question 44

Angiomyolipoma (AML)

Answer 44

Renal angiomyolipoma is a hypervascular hamartoma containing bood vessels (angio), smooth muscle (myo) and fat (lipoma). An AML is diagnosed on cross-sectional imaigng as a renal mass containing macroscopic fat. Angiography shows tortuous feeding arteries, which have a sunburst appearance on the parenchymal phase. Occasionally, small aneurysms are visible, which predispose to risk of hemorrhage, especially if the AML is \> 4 cm in diameter. In contrast to a renal arteriovenous fistula, AMLs do not feature arteriovenous shunting - that is, no veins will be opacified during arterial phase imaging. It is not always possible to differentiate an AML from RCC on angiography, so cross-sectional imaging is usually indicated if a suspected AML is diagnosed incidentally.

Question 45

Renal trauma

Answer 45

Renal trauma can be classified as blunt (\>80% of injuries), penetrating (such as gunshot or stab wound), or iatrogenic. Hematuria is usually present with renal trauma, regardless of etiology. A horseshoe kidney is especially susceptible to traumatic injury as it is not protected by the inferior ribs and may be compressed against the vertebral column. The Orgain Injury Scale (OIS) from the American Association for the Surgery of Trauma (AAST) classification is the most widely used classification of renal injury. Grade I-III include nonexpanding hematomas or parenchymal laceration without collecting system injury. These injuries are usually managed conservatively. Grade IV includes a deep parenchymal laceration that extends to the collecting system, causing the CT finding of extravasation of opacified urine on delayed imaging. Injury to the renal artery or vein with contained hemorrhage is also OIS grade IV, and is often treated with endovascular coil embolization as in the case above. Grade V (most severe) injury is a shattered kidney with avulsion of the renal hilum. Treatment is usually surgical. Other important vascular injuries not included in the OIS classification include renal artery thrombosis and renal artery pseudoaneurysm. Indications for endovascular treatment of renal trauma include active extravasation, dissection, or pseudoaneurysm. Treatment is usualy superselective coil embolization.

Question 46

Renal arteriovenous fistulas (AVFs) and malformations

Answer 46

Renal arteriovenous fistulas (AVFs) are almost always acquired, secondary to trauma or renal biopsy. Congenital intrarenal arteriovenous malformations are rare. The majority of renal AVFs are asymptomatic anf often heal spontaneously. When symptomatic, hematuria is the most common complaint. Less commonly, a renal AVF can lead to high-output cardiac failure or spontaneous retroperitoneal hemorrhage. Angiography of an AVF shows venous opacification during the arterial phase. Treatment is with embolization (coils, glue, or alcohol).

Question 47

Median arcuate ligament syndrome (MALS)

Answer 47

Median arcuate ligament syndrome (MALS) is celiac artery compression by the median arcuate ligament, a part of the diaphragmatic crura. Arterial compression worsens with expiration. While most patients are asymtpomatic, MALS may clinically present with crampy abdominal pain. MALS tends to occur in young, thin women. Angioplasty is not effective and stents are controversial due to high risk of device failure. Definitive treatment is surgical release of the median arcuate ligament to enlarge the diaphragmatic hiatus.

Question 48

SMA syndrome

Answer 48

SMA syndroe is compression of the duodenum between the aorta and the SMA and is also known as Wilkie syndrome. SMA syndrome occurs in thin children, burn victims, and patients who have lost weight.

Question 49

Nutcracker syndrome

Answer 49

Nutcracker syndrome is compression of the left renal vein between the aorta and the SMA. This is similar to SMA syndrome, but the renal vein is compressed instead of the duodenum. A posterior variant, called posterior nutcracker, is the compression of a retroaortic (or circumaortic) renal vein between the aorta and the vertebral body. Nutcracker syndrome can present with variable clinical symptoms including pain, hematuria, orthostatic proteinuria, pelvic congestion, and varicocele (in a male). Treatment depends on the symptoms. The majority of cases of hematuria resolve within two years of observation. If treatment is desired, angioplasty, and stenting of the renal vein can be performed.

Question 50

May-Thurner

Answer 50

May-Thurner syndrome is venous thrombosis of the left common iliac vein caused by compression from the crossing right common iliac artery. Chronic compression leads to a fibrous adhesion in the vein, predisposing to thrombosis. Treatment is endovascular thrombolysis followed by stenting.

Question 51

Measuring portal pressure

Answer 51

Direct portal vein (PV) pressure measurement requires traversing the hepatic paarenchyma and is thus invasive and impractical. Wedged hepatic vein pressure is routinely measured via an internal jugular vein catheter and is thought to equal PV pressure in most patterns. The portosystemic gradient (also known as the corrected sinusoidal pressure) represents the actual sinusoidal resistance to portal flow and is calcu to portal flow adn is calculated as: (Wedged hepatic vein pressure) - (free hepatic vein pressure) Portal hypertension is defined as a portosystemic gradient \>5 mm Hg.

Question 52

Collateral pathways seen in portal hypertension

Answer 52

Esophageal varices: Coronary vein -\> azygos/hemiazygous veins. Gastric fundal varices: Splenic vein -\> azygous veins. Splenorenal shunt: Splenic or short gastric -\> left adrenal/inferior phrenic -\> left renal vein. Mesenteric varices: SMV or IMV -\> iliac veins. Caput medusa: Umbilical vein -\>epigastric veins. Hemorrhoids: IMV -\> inferior hemorrhoidal veins.

Question 53

Transjugular intrahepatic portosystemic shunt (TIPS)

Answer 53

Transjugular portosystemic shunt (TIPS) lower elevated portal pressures by the creation of a direct connection between the portal vein and the hepatic vein. The most common indication for TIPS is treatment of variceal hemorrhage that cannot be controlled endoscopically. Other indicationsfor TIPS include refractory ascites and Budd-Chiari (hepatic vein thrombosis). Assessment of hepatic dysfunction is performed pre-procedure with either the Child-Pugh classification or Model for End-Stage Liver Disease (MELD) score. The Child-Pugh classification of hepatic dysfunction combines lab values (INR, bilirubin, and albumin) with clinical assessment (ascites and hepatic encephalopathy). The MELD score of hepatic dysfunction combines INR, bilirubin, and creatinine in a complex logarithmicformula. The higher the MELD score, the higher the post-TIPS mortality. Absolute contraindications to TIPS include: Right-sided heart failure, which will be worsened by TIPS, as right sided venous return increases. Severe active hepatic failure, as the post-TIPS shunting of blood beyond the hepatic sinusoids can cause liver function to worsen further. Severe hepatic encephalopathy, which TIPS can worsen. Portal vein patency should be established pre-procedure with cross-sectional or US imaging. Usually the right hepatic vein should be established pre-procedure with cross-sectional or US imaging. Usually the right hepatic vein is connected with the right portal vein via a covered stent. The right hepatic vein tends to be larger than the left. After the right hepatic vein is cannulated, wedged balloon CO2 occlusion venography is performed and the portal vein is retrogradely opacified. CO2 is the preferred contrast agent as it is 400 times less viscous than iodinated contrast adn is therefore easily able to pass through the hepatic sinusoids. The most demanding portion of the procedure is establishing access into a portal vein. Once a tract between the hepatic and portal circulation is secured, the tract is sequentially dilated and stented, aiming for a reductio of the portosystemic gradient to \<12 mm Hg. TIPS patency is followed by Doppler ultrasound.

Question 54

Inferior vena cava (IVC) filter placement

Answer 54

The purpose of an IVC filter is to reduce the risk of pulmonary embolism (PE) originating form a lower extremity deep venous thrombosis (DVT). Indications for filter placement include DVT and contraindication to anticoagulation; recurrent PE while anticoagulated; and high risk of developing DVT/PE in a patient with contraindication to anticoagulation, such as multi-trauma patient. The most common complication of IVC filter placement is access site thrombosis, followed by IVC thrombosis. IVC perforation occurs not uncommonly, but is almost always inconsequential. Filter fracture or embolization is rare. The first step of the procedure is an inferior vena cavogram, performed with a high-flow (pigtail) catheter. The cavogram guides the selection of filter type and placement location. If a duplicated IVC is present, in order to prevent a clot from circumnavigating the filter, either a single filter is placed above the IVC confluence or a filter is placed in each duplicated IVC. If pre-procedural imaging is not available, a clue to the presence of a duplicated IVC on initial cavography is the absence of iliac vein influx contralateral to the side injected. An IVC diameter \>28 mm generally requires a special bird's nest filter, which can be placed in IVCs ranging from 28-40 mm. If the IVC is \>40 mm in diameter, separate IVC filters can be inserted in each common iliac vein. The preferred location of the IVC filter is immediately inferior to the lowest renal vein, including any variant renal veins (circumaortic or retroaortic). Placement inferior to the lowest renal vein prevents the anomalous vein from acting as a conduit for clot propagation. Circumaortic left renal vein is an anatomic variant seen in 2-10% of the population, where the left renal vein is composed of two separate compoenents. One component passes anterior to the aorta (the normal configuration) and a second retroaortic component passes posterior to the aorta to meet the IVC. Retroaortic left renal vein is a slightly less common variant (seen in 2-7% of the population), where a single renal vein passes posterior to the aorta. A retrocardiac left renal vein usually joins the IVC more inferiorly than the right renal vein. Interrruption of the IVC with azygos continuation is a rare anaomaly where blood from the lower IVC flows into the azgyos and hemiazygos veins, into the thorax, and then into the right atrium. Interruption of the IVC with azygos continuation is associated with polysplenia and congenital heart disease. It is caused by embryologic failure of the right subcardinal vein to join the intrahepatic venous complex. The presence of preexisting IVC thrombus may interfere with the positioning of IVC filter, requiring higher than normal placement.

Question 55

Varicocele

Answer 55

A varicocele is dilation of the pampiniform venous plexus. Primary varicocele (most common) is due to absent or incompetent valves in the proximal gonadal vein causing venous reflux. Secondary varicocele is due to a mass obstructing venous return. Primary varicoceles are a highly prevalent and treatable cause of infertility. The vast majority of varicoceles are left sided as the left gonadal vein drains into the left renal vein, while the right gonadal vein drains directly into the IVC. A solitary right varicocele should prompt the workup for an obstructing retroperitoneal mass. Diagnosis by scrotal ultrasound shows a dilated (\>2 mm) venous plexus with a bag of worms appearance, which worsens on Valsalva maneuver. Treatment is coil embolization or surgical ligation of the gonadal vein; these have been shown to be equivalent in outcome.

Question 56

Biliary intervention overview and technique

Answer 56

Percutaneous transhepatic cholangiography (PTC) is the injection of contrast into the biliary tree throught a percutaneous approach, traversing the hepatic parenchyma. The two most common indications for PTC are relief of biliary obstruction and to provide biliary diversion in the case of ductal injury, which may be post traumatic or post surgical. Less common indications include percutaneous treatment of biliary calculi (endoscopic treatment is much more common) and adjunctive pre-surgical treatment prior to a biliary anastomosis. A biliary anastomosis is technically facilitated by having a pre-placed catheter to sew around. Pre-procedure prophylactic antibiotics are administered, as biliary stasis predisposes to bacterial overgrowth. Gram-negative coverage is needed, typically with levofloxacin. The right and left biliary trees are accessed using slightly different techniques. The right biliary tree is accessed via a right midaxillary line two-puncture approach. The needle should be inserted directly over the ribs, as the neurovascular bundle runs underneath each rib. A 22 gauge needle is inserted, parallel to the table and to the inferior border of the liver. Contrast is injected as the needle is withdrawn in an attempt to opacify the biliary tree. Once a bile duct is opacified, the needle is temporarily left in place and a second puncture is made with a 21 gauge need as low as possible to access the duct. Once the second needle has accessed a duct, a 0.018" wire is advanced, exchanged for a 5 or 6 Fr sheath, and subsequently a hydrophilic wire (such as a Roadrunner or Glidewire) is guided into the small bowel. The hydrophilic wire is exchanged for a stiff wire (e.g. Amplatz) and the biliary drain is placed. Extra sideholes may be manually cut, if necessary, to allow sideholes to extend from teh biliary puncture site to the bowel. The role of regular flushing is controversial. Some institutions advocate regular forward flushing, while others do not routinely flush. Regardless, a biliary drain should never be aspirated, as aspiration could draw up bowel contents into the biliary system and risk the development of cholangitis. Three-month preventative maintenance is recommended. The left biliary tree is accessed by a left subxiphoid approach. The left side is accessed in a similar manner to the right; however, ultrasound can often visualize dilated ducts, obviating the need for two punctures. If stent placement is required to treat a stricture, a metallic stent is usually only placed in patients with a life expectancy of less than 6-8 months. Most metallic stents cannot be removed and have a median patency of 6-8 months, although newer covered metal stents can be removed. Plastic stents, which are placed endoscopically, do allow regular exchange. An alternative to stent placement is an internal/external biliary drain, although this option is less comfortable for the patient due to the external drain. Most contraindications to PTC are relative. For instance, although an intrahepatic tumor (primary or metastasis) should not be traversed, a directly accessible bile duct may still be present. Similarly, ascites is a contraindication but therapeutic paracentesis can be first performed. Complications of percutaneous biliary drainage include sepsis, hemorrhage, bile leak, hemobilia (due to arterial-biliary fistula), and abscess.

Question 57

Bile duct injury

Answer 57

The most common cause of bile duct injury is iatrogenic from a laparoscopic cholecystectomy. A less common cause of bile duct injury is from orthotopic liver transplant. Treatment is to provide biliary diversion to a drainage bag to allow the leak to heal.

Question 58

Sclerosing cholangitis

Answer 58

Sclerosing cholangitis is a chronic inflammatory and fibrosing process leading to multifocal strictures of the intra- and extrahepatic biliary tree. Sclerosing cholangitis clinically presents with obstructive jaundice, malaise, and abdominal pain. It occurs more commonly in men and is associated with inflammatory bowel disease (ulcerative colitis). Sclerosing cholangitis ultimately leads to biliary cirrhosis and increases the risk of developing cholangiocarcinoma. Treatment of sclerosing cholangitis is liver transplant, although percutaneous biliary drainage can provide palliative relief for the symptoms of obstructive jaundice. Cholangiogram shows multifocal biliary structures throughout the intra- and extrahepatic biliary tree. The differential diagnosis of multifocal biliary strictures include: Sclerosing cholangitis, Primary biliary cirrhosis, Multifocal cholangiocarcinoma, Chronic bacteral cholangitis, AIDS cholangitis (usually associated with papilary stenosis).

Question 59

Malignant biliary obstruction

Answer 59

Unilateral biliary obstruction of either the right or left hepatic ductal system may be due to metastatic disease or primary malignancy of the bile ducts. In the majority of cases, only the affected billiary system requires treatment. Hilar obstruction, in contrast, is due most commonly to a hilar cholangiocarcinoma (Klatskin tumor), which most often requires two biliary drains, one each in the right and left ducts. Occasionally an anatomic anomaly, such as anomalous drainage of the right duct directly into the left duct, may allow complete drainage of a hilar obstruction with a single biliary drain. Pre-procedure MRCP may be helpful to delineat biliary anatomy.

Question 60

Acute cholecystitis

Answer 60

Percutaneous gallbladder drainage (cholecystectomy) is indicated for the treatment of acute calculous or acalculous cholecystitis in patients who are not surgical candidates. Cholecystectomy is a temporizing measure for reatment of calculous choleycstitis prior to cholecystectomy, but it may cure acalculous cholecystitis without surgery. Of note, cultures are negative in 40% of acute cholecystitis. Similar to percutaneous transhepatic cholangiography, prophylactic antibiotics aregiven. The two percutaneous approaches to the gallbladder are transhepatic and transperitoneal. Transhepatic (through the liver): In the transhepatic approach, a needle is inserted in the midaxillary line (either intercostal or subcostal) and directed towards the bare area of the gallbladder fossa through the liver under sonographic guidance. Transhepatic cholecystostomy has decreased risk of peritoneal bile leak, but increases the riks of liver laceration. The transhepatic approach is more commonly preferred. Transperitoneal (avoiding the liver): in the transperitoneal approach, the needle is directed into the gallbladder from a subcostal approach in the right anterior abdomen, beneath the liver margin. While there is less risk of damaging the liver, a transperitoneal approach carries an increased risk of peritoneal bile leak. Additionally, a transperitoneal approach necessitates penetration of the gallbladder fundus, with is the most mobile portion. The drainage tube must remain in place until the following criteria are met: Patient is clinically improved. There is a risk of sepsis if the tube is removed prematurely. Cystic duct and common bile duct are demonstrated to be patent on repeat cholangiogram. At least six weeks have passed since placement (regardless of transhepatic or transperitoneal approach), to allow a fibrous tract to develop extending from the gallbladder to the skin puncture. If the tube is removed prematurely there is a risk of bile peritonitis.

Question 61

Percutaneous nephrostomy indications and technique

Answer 61

The most common indication for percutaneous nephrostomy (PCN) is urinary diversion of an obstructed kidney due to stone, malignancy, or stricture. Pyonephrosis (pus in the collecting system) is an emergent indication for percutaneous nephrostomy. Less commonly, PCN may be used to place an anterograde ureteral stent if a retrograde ureteral stent is unable to be placed cystoscopically. Direct visualization of the collecting system is necessary. In most cases, urinary obstruction will lead to hydronephrosis, allowing ultrasound-directed puncture. If there is no dilation of the collecting system, intravenous contrast can be administered to opacify the nondilated collecting system and allow fluoroscopic guidance. The patient is positioned prone and a 22 gauge needle is used for direct posterior access. Bleeding complications can be minimized by entering the kidney in the relatively avascular zone of Brodel, which is defined as the plane between the ventral and dorsal renal artery branches. The optimal entry plane is therefore in the posterolateral kdiney directed towards a posterior calyx. Complications most commonly include bleeding and infection. Although transient hematuria occurs in nearly every patient, serious bleeding complications are rare. Of particular concern in cases of preexisting infection is the risk of sepsis caused by extensive manipulation.

Question 62

Percutaneous gastrostomy indications and technique

Answer 62

Esophageal, head and neck, and neurologic disease may necessitate percutaneous gastrostomy. Of note, there is strong evidence that gastrostomy does not improve survival or quality of life in eldery patients with dementia and decreased oral intake. A less common indication for gastrostomy is for long-term bowel decompression, for instance due to palliation of malignant bowel obstruction or prolonged ileus. Absolute contraindications to percuaneous gastrostoy include lack of appropriate window (such as colonic interposition), extensive gastric varices, and uncorrectable coagulopathy. A nasogastric tube is inserted under fluoroscopic guidance, through which the stomach is insufflated with air. Under fluoroscopic guidance, three T-fastener gastropexy clips are deployed to pexy the anterior wall of the stomach to the anterior abdominal wall. After each deployed T-fastener, intra-gastric position is confirmed with a small amount of contrast injected into the stomach. After the pexy clips are in place and the stomach is firmly fastened against the anterior abdominal wall, the definitive gastrostomy puncture is made and serially dilated. The gastrostomy can be used 24 hours after the patient is evaluated for peritoneal signs. The G-tube must remain in place for at least a month to form a mature transperitoneal tract.

Question 63

Normal arterial anatomy of the leg vasculature

Answer 63

The femoral artery is the continuation of the external iliac artery distal to the inguinal ligament. The femoral artery branches include: Deep femoral artery, the terminal branch to supply the deep muscles of the thigh. Superficial circumflex artery. Superficial femoral artery (SFA), which continues to supply the leg and foot. After passing posteriorly through the adductor hiatus, the SFA becomes the popliteal artery. From medial to lateral, the branches of the popliteal arteyr are: Posterior tibial artery (most medial). Peroneal artery (arises from the tibioperoneal trunk, along with the posterior tibial artery) Anterior tibial artery (most lateral; the only anterior artery of the lower leg). It is easy to remember that the anterior tibial artery is lateral because the only muscle bulk of the anterior lower leg is the lateral compartment and that muscle is the anterior tibialis.

Question 64

Atherosclerotic distal aortic occlusive disease (Leriche syndrome)

Answer 64

Leriche syndrome is chronic occlusive atherosclerotic disease of the distal abdominal aorta, producing the classical quartet of impotence, buttock claudication, absent femoral pulses, and cold lower extremities. Over time, extensive collaterals develop from the thoraco-abdominal aorta to the external iliac arteries, most commonly the anterior, middle and posterior pathways: Anterior: Thoracic aorta -\> internal thoracic aorta -\> superior epigastric artery -\> inferior epigastric artery -\> external iliac artery Middle: Abdominal aorta -\> SMA -\> IMA -\> superior rectal artery (terminal branch of IMA) -\> middle/inferior rectal arteries (via the path of Winslow) -\> retrograde through the internal iliac artery anterior division -\> external iliac artery Posterior: Abdominal aorta -\> intercostal and lumbar arteries -\> superior gluteal and iliolumbar arteries (branches of internal iliac artery posterior division) -\> deep circumflex iliac artery -\> external iliac artery.

Question 65

Iliac atherosclerotic disease

Answer 65

Percutaneous interventions are efficacious and well-tolerated for treatment of appropriate aortoiliac atherosclerotic flow-limiting disease. The 2006 second TransAtlantic Inter-Society Consensus (TASC-II) recommendations for treatment of aortoiliac and infrainguinal occlusive disease classify lesions as Types A through D (most severe). Percutaneous transluminal angioplasty (PTA) is the treatment of choice for noncalcified, concentric iliac stenosis \<3 cm in length (Type A). For lesions between 3 and 10 cm in length (Types B and C), either PTA or surgery coud be performed. Although TASC-II guidelines advocate surgery, many institutions would perform primary proximal iliac stenting for lesions \>3 cm in length. In contrast, PTA has only a limited role in treating stenosis \>10 cm (Type D) and in treating occlusions \>5 cm after thrombolysis. Subsequent to angioplasty, stenting is indicated if there is \>30% residual stenosis or \>10 mm Hg systolic pressure gradient at rest.

Question 66

Iliac artery aneurysm

Answer 66

An iliac artery aneurysm is defined as an iliac artery diameter \>1.5 cm. Repair is recommended once the diameter is \>3.0 cm. Iliac artery aneurysms are typically seen in older men and are associated with abdominal aortic aneurysms. They are most commonly associated with atherosclerosis. Iliac aneurysms may also be due to connective tissue diseases, such as Marfan syndrome. Cross-sectional imaging is recommended if an iliac stenosis is seen first on angiography. An iliac aneurysm with intra-luminal thrombus can stimulate an atherosclerotic stenosis on angiography. In appropriate candidates, endovascular stent-graft is the preferred treatment fo an iliac artery aneurysm. Mass effect from the aneurysm may cause neurologic and urologic symptoms, which case surgical treatment is recommended. Endovascular aneurysm repair cannot rapidly decrease aneurysm size, although endovascularly treated aneurysms do gradually decrease in size.

Question 67

Persistent sciatic artery

Answer 67

A persistent sciatic artery is a very rare vascular anomaly where the fetal sciatic artery persists to supply the majority of blood supply to the leg. The persistent sciatic artery arises from the internal iliac artery (usualy from the inferior gluteal artery) and continues distally to the popliteal artery. A rudimentary femoral artery may be present. A persistent sciatic artery may predispose to aneurysm formation.

Question 68

Pelvic vascular trauma

Answer 68

Pelvic trauma can lead to catastrophic hemorrhage from arterial injury. It is possible to exanguinate completely within the pelvis: A 3 cm diastasis fo the symphysis pubis doubles the potential intra-pelvic volume to approximately 8 liters. In the setting of active pelvic bleeding and pelvic fractures, angiography is usualy performed prior to orthopedic surgery. Active bleeding can be difficult to control surgically. The first step in treating a pelvic arterial injury is to perform a nonselective pelvic arteriogram, followed by selective bilateral internal iliac arteriograms of the anterior and posterior divisions. Because of the rich collateral supply in the pelvis, rapid nonselective gelfoam embolization of either the entire anterior or posterior division of the internal iliac artery is often acceptable. A potentially time-consuming superselective embolization should be avoided in the setting of life-threatening hemorrhage.

Question 69

Uterine artery embolization (UAE)

Answer 69

The two primary indications for uterine artery embolization (UAE) are symptomatic treatment of fibroids and postpartum hemorrhage. Polyinyl chloride particles are used. The goal of fibroid treatment is to produce hemorrhagic infarction of the hypervascular fibroids while maintaining adequate perfusion to the endometrium and myometrium, thus preserving future fertility. There is approximately a 1.25% serious complication rate for UAE, which is especially important to consider as many of these patients are otherwise healthy reproductive-age women. Serious complications include abscess, endometritis, and ovarian necrosis due to non-target embolization, leading to subsequent premature menopause.

Question 70

Chronic arterial occlusive disease

Answer 70

Peripheral vascular disease shares risk factors with coronary artery disease, including, smoking, diabetes, hypertension, hyperlipidemia, lack of exercise, and family history. Clinically, chronic peripheral atherosclerosis presents intially with claudication, which can progress to ischemic rest pain or tissu loss in severe cases. Claudication is usually first treated conservatively, with risk factor control, exercise, aspirin, and/or cilostazole (a platelet-aggregation inhibitor with vasodilator action). The most common locations for lower extremity athrosclerotic stenoses include the common iliac arteries, superficial femoral artery, popliteal artery, tibioperoneal trunk, and origins of the tibial arteries. The Rutherford classification clinically categorizes chronic limb ischemia. Category 0 is asymptomatic, category 1 is mild claudication, categories 2-3 are moderate to severe ischemia, category 4 is ischemic rest pain, and categories 5-6 are minor or major tissue loss, respectively. Revascularization should not be attempted if the limb is not viable. An ankle brachial index (ABI) should be performed in every patient with suspcted arterial occlusive disease. The ABI is the ratio of systolic blood pressure (SBP) in the ankles compared to the arms, and is calculated as: ankle SBP/brachial SBP. A decreased ABI suggests a hemodynamically significant stenosis between the great vessels and the ankles since the ankle blood pressure is less than the upper extremity blood pressure. An ABI \<0.9 is abnormal. An ABI between 0.5 and 0.9 usually correlates with intermittent claudication. Rest pain is usually present with an ABI \<0.4. Pulse-volume recordings characterize the Doppler waveform at multiple levels. The anatomic location of a lesion can be deduced by the change from a normal triphasic waveform to a biphasic (moderate stenosis) or flat waveform (severe stenosis/occlusion).

Question 71

Femoropopliteal disease

Answer 71

Similar to aortoiliac disease, the second TransAtlantic Inter-Society (TASC-II) consensus classifies femoropopliteal lesions and gives associated recommendations for intervention. Type A: Single stenosis =10 cm: Endovascular treatment is the treatment of choice. Type B: Multiple lesions (stenosis or occlusion), each \<5 cm; single lesion \<15 cm; Endovascular treatment is preferred, depending on patients comorbities and preference. Type C: Multiple stenoses or occlusion \>15 cm: Surgery is preferred, depending on patient's comorbidities and preference. Type D: Chronic total occlusion: Surgery is treatment of choice.

Question 72

Acute thromboembolic disease

Answer 72

Acute limb ischemia is an emergency, with a very different clinical and angiographic presentation compared to chronic atherosclerotic disease. In acute thromboemoblic disease, symptom onset is acute, with pain, pallor, poikilothermia (coldness), pulselessness, and paresthesias. Blue toe syndrome is acute thromboembolism in the toes. The most common embolic source is a left atrial thrombus, with atrial fibrillation a significant risk factor. Echocardiography is indicated in the workup. Angiography shows an acute cutoff of the affected vessel, often with a meniscus sign. Significant atherosclerotic disease may be absent. Treatment options include surgical embolectomy, surgical bypass graft, and endovascular thrombolysis. When attempting to treat endovascularly, a hydrophilic wire is used to cross the lesion. A multi-sidehole infusion catheter is placed across the thrombus and tissue plasminogen activator (tPA) is infused at 0.5 mg/h for 48-72 hours. While receiving intra-arterial tPA, the patient must be cared for in the ICU, with regular monitoring of hematocrit and fibrinogen. TPA infusion should be slowed if the fibrinogen decreases to \<150 mg/dL and stopped if it reaches \<100 mg/dL.

Question 73

Popliteal aneurysm

Answer 73

A popliteal artery aneurysm is defined as a popliteal artery measuring 8 mm or more. Popliteal aneurysms are almost always due to atherosclerosis and are associated with other atherosclerotic aneurysms. Approximately 20% of patients with a popliteal aneurysm also have an aortic aneurysm, and up to half have bilateral popliteal aneurysms. Popliteal aneurysms are usually asymptomatic. When symptomatic, the typical presenting symptoms is distal ischemia due to embolism. Popliteal aneurysm rupture is rare. Treatment is recommended for all symptomatic popliteal artery aneurysms and asymptomatic aneurysms \>2 cm in diameter. Treatment is with endovascular stent-graft or surgical bypass.

Question 74

Buerger disease

Answer 74

Buerger disease is a medium and small vessel occlusive vasculitis that affects the lower extremities (most commonly) and the hands (less commonly). It is seen in adult male smokers and should be clinically suspected in a middle-aged male presenting with claudication. On angiography, there are segmental stenoses of the medium and small arteries in the leg, with typical corkscrew collaterals in th vasa vasorum. The larger arteries, including the common femoral artery, superficial femoral artery, and popliteal artery, are typically spared. Primary treatment of Buerger disease is smoking cessation.

Question 75

Popliteal entrapment syndrome

Answer 75

Popliteal entrapment syndrome is compression of the popliteal artery by a calf muscle or fibrous band, most commonly an aberrant medial head of the gastrocnemius. It is an important cause of exercise-induced claudication in healthy young males. Bilateral involvement is common. There are six different types of popliteal entrapment, depending on the deviation of the aberrant muscle and the popliteal artery. However, by far the most common anomalies invovle the medial head of the gastrocnemius, with either medial deviation (type I) or no deviation (type II) of the popliteal artery. Treatment is surgical release of the offending muscle (usually the medial head of the gastrocnemius). Angiography is only used for diagnosis, not therapy.

Question 76

Cystic adventitial disease

Answer 76

Cystic adventitial disease is a rare cause of distal claudication where one or more mucoid cysts in the adventitia surrounding the popliteal artery leads to lumenal compression. Clinically, most patients are middle-aged men presenting with claudication. MRI is the best diagnostic tool, as the cystic component, as the cystic component can be readily identified with typical T2 hyperintensity. Treatment is surgical resection of the cyst or surgical bypass. Cyst aspiration can also be performed, but the cyst almost always recurs.

Question 77

Normal vascular anatomy of the upper extremity

Answer 77

The basilic vein, located medial and superficial to the brachial veins, is the first choice for peripherally inserted catheter (PICC) placement The cephalic vein adds an extra curve as it joins the axillary/subclavian vein, but is generally the second choice if the basilic is not available. There is risk of damaging the median nerve with placement in a brachial vein as the median nerve lies superficial to the brachial veins. A PICC should not be placed in a patient with chronic renal failure who may need a fistula in the future. Central acess using the neck veins should be used instead.

Question 78

Overview of thoracic outlet syndromes

Answer 78

Thoracic outlet syndromes are a controversial spectrum of disorders caused by compression of either the brachial plexus, subclavian artery, or subclavian vein, clinically presenting with upper extremity paresthesias, pain, numbness, and/or coolness. The interscalene triangle is the space bounded by the anterior scalene muscle, the middle scalene muscle, and the first rib. The brachial plexus and subclavian artery pass through the interscalene triangle. In contrast, the subclavian vein does not pass through the interscalene triangle, but instead runs anterior to the anterior scalene muscle.

Question 79

Neurogenic thoracic outlet syndrome

Answer 79

The neurogenic form of thoracic outlet syndrome is the most common manifestation, due to mechanical compression of the brachial plexus.

Question 80

Subclavian artery compression

Answer 80

Compression of the subclavian artery clinically presents with hand or finger pain, numbness, paresthesias, or coolness. Raynaud phenomenon is common. Raynaud phenomenon is intermittent distal vasospasm caused by cold temperature or other external stimuli. Symptoms worsen with arm abduction. Adson's maneuver is a test for subclavian artery compression at the thoracic outlet. First, the radial artery is palpated in neutral position. Then the patient's head is turned to the contralateral side while they inhale. In arterial thoracic outlet syndrome, the radial pulse will be reduced with this maneuver. A mechanical compression is almost always present. Over 70% of patients with subclavian artery compression have a cervical rib. Other causes of subclavian artery compression include an accessory scalene muscle (scalenus minimus), enlargement of the anterior scalene muscle, and well-developed musclulature. Potential complications include arterial mural thrombus, aneurysm, and distal embolizationn. The hands should always be evaluated for signs of distal emboli. The preferred treatment of subclavian artery compression is surgical thoracic outlet decompression (e.g., resection of a cervical rib) and repair of the subclavian artery if an aneurysm is present. Endovascular arterial thrombolysis may be performed adjunctively, weighed against the risk for distal embolization.

Question 81

Paget-Schroetter syndrome (subclavian vein compression)

Answer 81

Paget-Schroetter syndrome is compression and thrombosis of the subclavian vein as it enters the thorax and is usually seen in muscular young men. Chronic compression causes intimal hyperplasia, which leads to subclavian vein thrombosis. Paget-Schroetter syndrome clinically presents with upper-extremity swelling or pain worsened with effort. During diagnostic venography, it is necessary to evaluate the arm both in neutral position and abducted. Both sides should be evaluated. Frequently, both subclavian veins are compressed, even if only one side is symptomatic. Treatment is thrombolysis, then subsequently surgical thoracic outlet decompression. If there is residual stenosis following thrombolysis, surgical decompression should generally be performed prior to angioplasty. However, if pre-procedural imaging demonstrated no mechanical cause then angioplasty can be performed, as in the case above. Stents should generally not be used, especially if there is a mechanical obstruction, due to high risk of device failure.

Question 82

Subclavian steal syndrome

Answer 82

Subclavian steal syndrome is a proximal stenosis or occlusion of the subclavian artery, which leads to retrograde flow from the vertebral artery distal to the flow-limiting lesion. Subclavian steal syndrome clinically presents with vertebrobasilar insufficiency or syncope exacerbated by arm exercise. There may occasionally be direct signs of brachial artery insufficiency, wuch as extremity coolness or even fingertip necrosis. Subclavian steal is best diagnosed with angiography. The early arterial phase shows the proximal subclavian flow-limiting lesion and the later arterial phase shows retrograde flow from the vertebral artery into the subclavian. Treatment options include surgical bypass or angioplasty of the flow-limiting lesion.

Question 83

Arteriovenous fistula

Answer 83

A surgical fistula for dialysis acess provides good long-term patency (85% at two years), but requires several months to "mature" and about 30% of fistulas fail to mature. A fistula is mature when the veins have enlarged sufficiently to allow the high flow rates for dialysis. Once mature, a fistula can remain patent even with relatively low flow rates. The two common fistula locations are: Radial artery -\> cephalic vein at the wrist. Brachial artery -\> variable veins in the forearm. Common causes of late fistulas include venous outflow stenosis and perianastomotic venous stenosis.

Question 84

Polytetrafluorethylene (PTFE) graft

Answer 84

A polytetrafluorethylene (PTFE) graft is a short bridge of synthetic graft material placed surgically between an adjacent artery and vein. Grafts have only 50% patency at 2 years, but are able to be used sooner than fistulas. Grafts require higher flow rates to remain patent compred to fistulas. Similar to a fistula, the most common cause of graft failure is a venous stenosis, either at the venous anastomosis or outflow vein.

Question 85

Clinical evaluation of surgical dialysis access

Answer 85

A pulsatile fistula with lack of thrill suggests venous outflow obstruction. High access recirculation at dialysis suggests venous outflow stenosis. Weak pulse and poor thrill suggests arterial inflow stenosis. A pulseless fistula suggests thrombosed fistula.

Question 86

Venous stenosis of surgical dialysis access

Answer 86

Venous outflow stenoses are typically treated with angioplasty, often requiring high-pressure or cutting balloons to dilate the fibrotic lesions. The goal of the procedure is to restore a palpable thrill and pulse, or to restore the venous to brachial artery pressure ratio to less than 0.4.

Question 87

Thrombosis of surgical dialysis access

Answer 87

Both arteriovenous fistulas and PTFE grafts may become thrombosed. In general, PTFE grafts are simpler to declot compared to fistulas as the thrombus is usually limited to the graft. Thrombosis is often secondary to venous stenosis, which must be treated as well. Either pharmacologic or mechanical thrombolysis can be performed.

Question 88

Hypothenar hammer

Answer 88

Hypothenar hammer syndrome represents injury to the ulnar artery as it crosses the hamate bone. Chronic repetitive trauma causes the ulnar artery to be chronically traumatized at the hamate, leading to intimal injury, thrombus, aneurysm or pseudoaneurysm. The classic clinical history of hypothenar hammer syndrome is a jackhammer operator iwth ischemia of the fourth and fifth digits. Imaging shows occlusion of the ulnary artery, often with distal embolic occlusions due to distal thrombi, usually in the 4th and 5th fingers. Treatment is surgical, as there if often ulnar injury not apparent on angiography.

Question 89

Buerger disease (hands)

Answer 89

As previously discussed, Buerger disease is a small and medium vessel vasculitis that typically occurs in male smokers. It more commonly involves the legs but may also involve the hands, where it may present with ischemia, ulcerations, and even gangrene. Small vessel occlusions and prominent corkscrew collaterals are the typical angiographic features.

Question 90

Raynaud disease

Answer 90

Raynaud disease is small arterial vasospasm triggered by cold temperature. On imaging, there is decreased perfusion of the distal digital arteries, with improvement upon warming or vasodilator adminimstration. Raynaud disease is associated with scleroderma and other connective tissue disorders.

Question 91

Thromboembolic disease

Answer 91

Thromboembolic disease of the upper extremities is most commonly caused by cardiac emboli (of which atrial fibrillation is a common cause). Less commonly, a subclavian artery aneurysm may be the source of the thrombus. If the source of emboli is central (such as the heart), bilateral disease would be expected, while a unilateral lesion would show unilateral emboli. The characteristic imaging feature of distal thromboembolic disease is occlusion of distal small arteries of the hand.