Abdominal vascular Flashcards
In mammals what three veins play a part in creating the caudal vena cava?
Supracardinal, subcardinal, vitelline veins
Give a (general) description of CT features of segmental caudal vena cava aplasia? CT and MRI features of canine segmental caudal vena cava aplasia - JSAP (2009)
All dogs have a missing normla CVC segment between kidneys and liver - renal and post-renal (cranial to the kidneys) caval blood was directed instead through shunt vessel into the right or left azygos vein. Additionally, in some cases, the common iliacs did not form the caudal aspect of the CVC, and instead ran cranially as two separate vessels (duplication), until they dumped into the azygos vein.
How would you characterize these vessel anomalies?
CT and MRI features of canine segmental CVC aplasia. JSAP (2009).
A - Normal
B - Right lateral cavo-right azygos shunt
C - Right medial, cavo-right azygos shunt
D - Aneurysmal right medial cavo-right azygos with isthmian connection to the azygos vein.
E - Split CVC right medial cavo-right azygos shunt
F - Dorsal cavo-r azygos continuation
G - Aneurysmal cavo-left azygos with shunting portal vessel
H - Split CVC aneurysmal cavo-left azygos shunt and shunting portal vessel.
Seeing a CVC abnormality on CT should make you raise your suspicion for…?
Imaging diagnosis - Portal vein aplasia and interruption of CVC in 3 dogs - VRU 52.4
CT and MRI features of canine segmental CVC aplasia - JSAP 2009
Portal shunting
Deep vein thrombosis (seen in humans, correlation in animals was not strong).
Really - you should look for other congenital abnormalities.
What breeds and sex are predisposed to caudal vena cava duplication?
MDCT and US characteristics of CVC duplication in dogs. VRU 55.5 (2014)
Westies, Yorkies, Poodles, Maltese (also the breeds predisposed to shunt formation).
Females
What are causes for CVC collateral circulation to form?
CT characteristics of collateral venous pathways in dogs with CVC obstruction. VRU 55.5 (2014).
Any causes of obstruction or increases in flow resistance: neoplasia, trauma, thrombosis
What are the four main venous collateral pathways identified secondary to CVC obstruction?
Which is the most common seen in dogs/humans?
CT characteristics of collateral venous pathways in dogs with CVC obstruction. VRU 55.5 (2014).
1) Superficial collateral - iliac circumflex veins drain from the common iliac veins intot he superficial, subcutaneous venous pathways
2) Intermediate collateral - enlargement of gonadal and periureteral veins –> drains to left renal and CVC
3) Portal collateral - enlarged left colic vein and cranial mesenteric vein in rectal region –> drains tot he portal vein
4) Deep collateral - enlargement of lumbar veins and drain blood from CVC to right azygos vein
How can you differentiate between a cavoportal or portocaval shunt?
CT characteristics of collateral venous pathways in dogs with CVC obstruction. VRU 55.5 (2014). Web
Hepatopetal (towards the liver) –> Cavoportal
Hepatofugal (away from the liver) –> portocaval
Level of attenuation: If matches the CVC - cavoportal pathway. If it matches the portal vessels - portocaval shunt
Describe how to perform a complete dual phase CTA for evaluation of a portosystemic shunt using a test bolus.
Dual-phase CTA of normal canine portal and hepatic vasculature. VRU 45.2 (2004).
Pre-contrast (full abdomen)
Dynamic scan: performed at the porta hepatis. Cine loop is imaged sequentially to evalutae contrast enhancement after low dose (185mg I/kg) administered. Injection rate of 5ml/s. ROI over the CSA of aorta, PV and hepatic artery. Time/attenuation curve is created.
Dual phase CTA: Calculated delay times are entered into scan parameters. 880mg I/kg given at same rate. Arterial phase begun at time of appearance of contrast in aorta (caudal –> cranial). Portal phase was intiiated after peak portal enhancement, or following reset time between phases. Cranial –> caudal
Define the characteristics of a time attenuation curve created after a dynamic CT scan.
Dual phase-CTA of normal canine portal and hepatic vasculature. VRU 45.2 (2004). Web.
Time of arrival - time at which vessel of interest has reached 15% of its peak contrast enhancement.
Time of peak enhancement - time it takes for a vessel to reach its highest peak attenuation.
What are the approximate scan delays for time of appearance of contrast in CTA study for aorta/PV, and time to peak enhancement for aorta/PV?
Dual-phase CTA of normal canine portal and hepatic vasculature. VRU 45.2 (2004).
Time of appearance:
Aorta - 8s
PV - 15s
Peak enhancement
Aorta - 12s
PV - 33s
Describe how to perform a CTA using a bolus tracking? What are drawbacks?
Thoracic CV MDCTA in companion animals. VRU 55.3
Pre-contrast (full abdomen)
Full dose of contrast administered followed by saline flus. A threshold is set (an increase in aortic HU by 30%) will trigger the CT machine to run.
Drawbacks: delay of machine
List the order of the portal vessel supply
Millers anatomy
Dual phase CTA of normal canine portal and hepatic vasculature. VRU 45.2
Formation - at the confluence of caudal mesenteric and cranial mesenteric veins. Splenic vein (blood from spleen, stomach, pancreas, left gastric vein) - T13-L1 Gastroduodenal vein (drains portions of the pancreas, stomach, duodenum, omentum) - T11
Where does the azygos vein form, and where do they drain?
Embryologically - how do these form?
Computed tomographic and magnetic resonance imaging features of canine segmental caudal vena cava aplasia. Journal of Small Animal Practice. 50.7 (2009)
Right azygos (predominant vein) - forms approximately at L1 - dorsal to the aorta before moving towards the right side. Drains into the cranial vena cava - extrapericardially
Left hemiazygos vein - drains at the coronary sinus (confluence of coronary veins tinto the right atrium) intrapericardially.
Supracardinal vessel - regressed on the left side. Stays intact on the right side.
What are common presenting complaints of dogs with arterioportal fistulas?
Zwingenberger, A., et al. CTA of arterioportal fistulae. VRU 46.6 (2005)
Similar to signs for dogs with PSS and portal hypertension: hepatic encephalopathy, ascites, lethargy
Two time attenuation charts are included. What is the difference between these. What is the diagnosis?
The first chart is a normal dog. Portal vein has a gradual increase in HU without a substantial peak/plateau.
Second chart is consistent with a fistula. The intrahepatic portal veins and portal vein have to high/rapid of a peak/plateau. These changes are consistent with enhancement during the arterial phase - consistent with an arterioportal fistula.
Zwingenberger. CTA of arterioportla fistulae. VRU 46.6 (2005).
