Kidneys, Ureters, Bladder, Urethra Flashcards
1
Q
Renal Mass Protocol Multiphase CT
What are the phases?
The timing of each?
The significance of each?
A
- A renal mass protocol CT consists of at least three phases of data acquisition, with each phase providing important information to aid in the diagnosis of a renal mass.
- Unenhanced phase: Necessary as a baseline to quantify enhancement.
- Nephrographic phase (100-second delay): The nephrographic phase is the critical phase for evaluating for enhancement, comparing to the unenhanced images.
-
Pyelographic phase (15-minute delay; also called the excretory phase): The pyelographic phase is helpful for problem-solving and to diagnose potential mimics of cystic renal masses.
- The pyelographic phase can distinguish between hydronephrosis (will show dense opacification in the pyelographic phase) and renal sinus cysts (will not opacify).
- Reflux nephropathy may cause a dilated calyx that can simulate a cystic renal mass on the nephrographic phase. The pyelographic phase would show opacification of the dilated calyx.
- The pyelographic phase is also useful to demonstrate a calyceal diverticulum and to show the relationship of a renal mass to the collecting system for surgical planning.
- Optionally, a vascular phase can be performed for presurgical planning.
2
Q
Evaluating Enhancement of Renal Masses
What is the most important characteristic to distinguish between a benign and malignant non-fat containing renal mass?
If a mass has intralesional fat and also enhances, what is it?
On CT, what is considered enhancement?
How about on MR?
What is considered as a lesion “too small to characterize”?
A
- The presence of enhancement is the most important characteristic to distinguish between a benign and malignant non-fat-containing renal mass (a lesion containing intralesional fat is almost always a benign angiomyolipoma, even if it enhances).
- On CT, enhancement is quantified as the absolute increase in Hounsfield units on postcontrast images, compared to pre-contrast:
- <10 HU: No enhancement. 10-19 HU: Equivocal enhancement. >20 HU: Enhancement.
- On MRI, enhancement is quantified as the percent increase in signal intensity as measured on post-contrast images:
- <15%: No enhancement. 15-19%: Equivocal enhancement. >20%: Enhancement.
- Lesions are considered “too small to characterize” if the lesion diameter is smaller than twice the slice thickness. For instance, using 3 mm slices, a lesion less than 6 mm cannot be accurately characterized based on attenuation or enhancement.
3
Q
What are the renal mass biopsy indications
A
- After full imaging workup is complete, there are several well-accepted indications for percutaneous renal mass biopsy:
- To distinguish renal cell carcinoma from metastasis in a patient with a known primary.
- To distinguish between renal infection and cystic neoplasm.
- To definitively diagnose a hyperdense, homogeneously enhancing mass (after MRI has been performed), which may represent a benign angiomyolipoma with minimal fat versus a renal cell carcinoma.
- To definitively diagnose a suspicious renal mass in a patient with multiple comorbidities for whom nephrectomy would be high risk.
- To ensure correct tissue diagnosis prior to renal mass ablation.
4
Q
Renal Cell Carcinoma
It represents what percent of all cancers?
Risk factors?
Most common subtype?
Which one enhances the most?
Which one is the hypovascular subtype?
What is a renal “adenoma”?
The subtype with the best prognosis?
Which subtype is known to affect mostly young adult males with sickle cell trait? Prognosis of this subtype?
A
- Renal cell carcinoma - RCC is a relatively uncommon tumor that arises from the renal tubular cells. It represents 2-3% of all cancers.
- Risk factors for the development of RCC include smoking, acquired cystic kidney disease, VHL, and tuberous sclerosis.
-
Clear cell is the most common RCC subtype (~75%), with approximately 55% 5-year survival.
- Clear cell RCC tends to enhance more avidly than the less common subtypes.
- Clear cell can be sporadic or associated with VHL.
-
Papillary RCC is a hypovascular subtype, with a 5-year survival of 80-90%.
- Papillary RCC tends to enhance only mildly due to its hypovascularity.
- A renal “adenoma” is frequently seen on autopsy specimens and is a papillary carcinoma <5 mm.
- Chromophobe is the subtype with the best prognosis, featuring a 90% 5-year survival.
- Collecting duct carcinoma is rare and has a poor prognosis.
-
Medullary carcinoma is also rare, but is known to affect mostly young adult males with sickle cell trait.
- Medullary carcinoma is an extremely aggressive neoplasm, with a mean survival of 15 months, not helped by chemotherapy.
5
Q
Renal Cell Carcinoma Subtypes
A
- Clear cell
- Collecting duct
- Chromophobe
- Papillary
- Medullary
MNEMONIC: CCCPM
6
Q
Staging of Renal Cell Carcinoma
Staging is based on what system?
Which stages are usually resectable?
Describe each stage.
A
- Staging of renal cell carcinoma is based on the Robson system, which characterizes fascial extension and vascular/lymph node involvement. Stages I-III are usually resectable, although the surgical approach may need to be altered for venous invasion (stages IIIA and IIIC).
- Stage I: Tumor confined to within the renal capsule.
- Stage II: Tumor extends out of the renal capsule but remains confined within Gerota’s fascia.
- Stage III : Vascular and/or lymph node involvement.
- IIIA: Renal vein involvement or IVC involvement.
- IIIB: Lymph node involvement.
- IIIC: Venous and lymph node involvement.
- Stage IVA : Tumor growth through Gerota’s fascia
- Stage IVB : Distant metastasis.
7
Q
Renal Angiomyolipoma
What is it composed of? Sporadic vs associated with what syndrome? In the case it is associated with a syndrome, what can happen with the AMLs then?
What is the risk if they get too big? What size is the cut-off?
Imaging characteristic? Calcifications?
MRI and US appearance?
A
- AML is the most common benign renal neoplasm, composed of fat, smooth muscle, and disorganized blood vessels. The majority are sporadic, but 40% are associated with tuberous sclerosis (where AMLs are bilateral, with multiple renal cysts).
- AML has a risk of hemorrhage when large (>4 cm), thought to be due to aneurysmal change of the vascular elements. Small, asymptomatic AMLs are not typically followed or resected.
- A early pathognomonic imaging finding is the presence of macroscopic fat in a non-calcified renal lesion. The non fat-containing portion enhances avidly and homogeneously. Calcification is almost never present.
- On MRI, the fat component will follow retroperitoneal fat on all sequences and will saturate out on fat-saturated sequences. Intracytoplasmic lipid is not a feature of AML, so there should be no significant signal drop-out on dual-phase MRI.
- Approximately 4% of AMLs will not contain visible macroscopic fat and will appear as a hyperdense enhancing mass. MRI is the next step, with the T2-weighted images the most useful to distinguish from renal cell carcinoma in some cases.
- A T2 hyperintense mass suggests RCC (clear cell subtype) and the patient can proceed to surgery.
- A T2 hypointense mass is nonspecific and can represent either RCC (papillary type) or AML with minimal fat. Although an AML typically would enhance more avidly than a papillary RCC, biopsy is warranted for definitive diagnosis.
- AML appears hyperechoic on ultrasound, although up to 1/3 of renal cell carcinomas may also be hyperechoic and ultrasound is thus unreliable to distinguish AML from RCC.
8
Q
Renal Oncocytoma
Imaging features?
How to differentiate this with RCC?
What complicates the pathologic diagnosis?
A
- Oncocytoma is the most commonly resected benign renal mass and has overlapping imaging findings with renal cell carcinoma.
- Imaging features can suggest oncocytoma, but imaging features are not specific and cannot be reliably differentiated from RCC.
- The imaging features suggestive of oncocytoma are homogeneous enhancement and a central scar.
- Complicating the pathologic diagnosis, oncocytic cells can sometimes be found in the rare chromophobe RCC subtype. The pathologist can usually distinguish oncocytoma from the more common clear cell and papillary renal cell carcinoma subtypes.
9
Q
Renal Lymphoma
What is more common: primary or secondary?
What are the disease patterns of renal involvement by lymphoma and which is most common?
A
- Primary renal lymphoma is rare, as the kidneys do not contain native lymphoid tissue. However, the kidneys may become involved from hematogenously disseminated disease or spread from the retroperitoneum.
- Renal involvement of lymphoma has several patterns of disease:
- Multiple lymphomatous masses (most common pattern; seen in 50% of cases of renal lymphoma).
- Solitary renal mass.
- diffuse lymphomatous infiltration, causing nephromegaly.
- Direct extension of retroperitoneal disease.
10
Q
Non-neoplastic Solid Renal Masses
Sometimes renal masses can represent a non-neoplastic lesion - give two examples.
What can mimic a hypervascular renal mass?
What would asymmetric enhancement of the renal vein on the affected side clue to?
A
- Infection, especially focal pyelonephritis, can masquerade as a solid renal mass. A renal abscess may be difficult to differentiate on imaging from a cystic renal cell carcinoma.
- Renal arteriovenous malformation will avidly enhance and can mimic a hypervascular renal mass. One clue to the presence of an AVM would be asymmetric enhancement of the renal vein on the affected side, due to early shunting of venous blood.
11
Q
Renal Pseudotumors
What are they?
Describe them!
A
- Renal pseudotumors are normal variations of renal morphology that may mimic a renal mass.
- Hypertrophied column of Bertin: The columns (septa) of Bertin are normal structures that anchor the renal cortex to the hilum and create the separations between the renal pyramids. When hypertrophied, the columns of Bertin may mimic a renal mass.
- Persistent fetal lobation/lobulation: In normal fetal development, the fetal kidneys are divided into discrete lobes. Occasionally these lobulations persist in adulthood, producing an indentation of the renal cortex. This indentation can cause an adjacent focal bulge that simulates a renal mass. This pseudomass can usually be distinguished from a true mass by the presence of septa of Bertin on either side.
12
Q
Name the syndromes with renal masses
Which ones have increased risk of RCC?
A
- VHL
- Birt-Hogg-Dube
- Tuberous Sclerosis
- They all have an increased risk of RCC!
13
Q
VHL
What is it? What does it lead to?
What is the primary manifestation of VHL in the GU system?
Other GU manifestations?
CNS manifestations?
Pancreatic and hepatic manifestations?
A
- von Hippel-Lindau is an autosomal dominant multiorgan syndrome caused by a mutation in the VHL tumor suppressor gene on chromosome 3, which leads to cysts and neoplasms in multiple organs.
- The primary manifestation of VHL in the genitourinary system is bilateral or multifocal renal cell carcinomas, most commonly the clear-cell subtype.
- Other genitourinary manifestations of VHL include multifocal pheochromocytoma and renal cysts.
- Central nervous system manifestations of VHL include hemangioblastoma of the brainstem, cerebellum, or spinal cord.
- Pancreatic and hepatic manifestations include malignant neuroendocrine pancreatic tumor, pancreatic serous cystadenoma (a benign neoplasm), and pancreatic/hepatic cysts.
14
Q
Burt-Hogg-Dube Syndrome
What is another name for this syndrome?
What is it characterized by?
A
- Folliculin gene-associated syndrome (FLCN-S) or Birt-Hogg-Dubé (BHD) syndrome is a genetic multisystemic autosomal dominant disease mainly characterised by:
- Multiple lung cysts and secondary spontaneous pneumothoraces
- Multiple bilateral renal tumours (particularly chromophobe renal cell cancer and oncocytoma)
- Cutaneous manifestations (angiofibromas, perifollicular fibromas, acrochordons, fibrofolliculomas, etc.)
- MNEMONIC: (Hogg-Skin, Burt-Lungs, Dube-Kidneys)
15
Q
Tuberous Sclerosis
What is it?
How does it manifest clinically?
Most common renal manifestation? What % of patients with TS will have at least one AML?
How often do you see renal cysts in TS pts?
How often do you get RCC in TS pts?
TS manifestation in heart? in the lung? on Skin?
A
- Tuberous sclerosis is an autosomal dominant neurocutaneous disease caused by a tumor suppressor gene mutation. It manifests clinically with seizures, developmental delay, and (mostly) benign tumors in multiple organ systems.
- The most common renal manifestation of tuberous sclerosis is multiple bilateral renal angiomyolipomas. Approximately 50% of patients with TS will have at least one AML.
- Renal cysts can be seen in ~25%.
- The relative risk of renal cell carcinoma is increased in patients with TS, and occurs in approximately 2-3% of patients. Diagnosis of renal cell carcinoma is complicated by the abnormal kidneys that may have multiple cysts and/or AMLs.
- In the heart, the most common neoplasm is a rhabdomyoma. A cardiac rhabdomyoma may be present during fetal life and can be detected by fetal ultrasound.
- In the lung, a process of smooth muscle proliferation identical to lymphangioleiomyomatosis can occur, causing cystic replacement of lung parenchyma.
- It has been suggested that the abnormal smooth muscle in the lung in patients with TS represents genetically identical metastatic smooth muscle from a renal angiomyolipoma.
16
Q
What are the two most common entities to cause a cystic renal mass?
A
- A cystic renal mass may be neoplastic or infectious; the two most common entities to cause a cystic renal mass are renal cell carcinoma and renal abscess.
17
Q
Neoplastic Differential of a Cystic Renal Mass
What are they?
A
- Cystic renal cell carcinoma. Although renal cell carcinoma most commonly presents as a solid renal mass, it can also manifest as a cystic renal mass.
- Multilocular cystic nephroma
- Mixed epithelial and stromal tumor
18
Q
Multilocular Cystic Nephroma
What is it? Age distribution?
Characteristic (but non-specific) feature in children?
In adults what can it be indistinguishable from?
How about in children?
A
- Multilocular cystic nephroma is a benign cystic neoplasm with enhancing septa that occurs in a bimodal age distribution in baby boys and middle-aged women. A characteristic but nonspecific feature is the propensity to herniate into the renal pelvis, causing hydronephrosis.
- In children, multilocular cystic nephroma can be indistinguishable from cystic Wilms tumor.
- In adults, multilocular cystic nephroma can be indistinguishable from cystic renal cell carcinoma.
19
Q
Mixed Epithelial and Stromal Tumor
What is it?
Typically found in whom?
Appearance?
A
- Mixed epithelial and stromal tumor is a benign neoplasm composed of epithelial and mesenchymal elements.
- Typically found in middle-aged women.
- MEST may appear as either a solid or cystic mass.
20
Q
Non-neoplastic differential of a cystic renal mass
A
- Renal abscess is a contained purulent collection within the kidney.
- Hemorrhagic renal cyst, which will not have any enhancing component.
21
Q
Role of MRI in evaluation of a complex cystic renal mass
When is it most useful?
What is it more sensitive for compared to CT?
Calcifications are more difficult or easier to detect compared to CT?
A
- MRI has a limited role in the evaluation of a cystic renal mass. The key advantage of MRI is more accurate enhancement characterization, as MRI does not suffer from the CT phenomenon of pseudoenhancement due to beam hardening from adjacent, densely enhancing renal parenchyma.
- The increased accuracy of MRI to characterize enhancement is most useful to distinguish a Bosniak IIF from a Bosniak III lesion. Thickening of a septation or cyst wall that shows measurable enhancement defines a Bosniak III lesion.
- MRI is more sensitive for detecting septations compared to CT.
- Calcifications are more difficult to detect with MRI.
22
Q
Simple Renal Cyst
How common are they?
CT appearance?
MR appearance?
A
- Simple renal cysts are extremely common, found in approximately 50% of patients over age 50. A simple renal cyst is an incidental lesion that requires no follow-up, even when large.
- On CT a simple cyst must attenuate close to 0 Hounsfield units, not contain any enhancing components, and have a thin imperceptible wall.
- On MRI, a simple cyst must be hypointense on T1-weighted images, hyperintense on T2-weighted images, and not contain any enhancing component.
23
Q
Renal Sinus Cyst
What are the two classifications?
Compare and contrast them.
A
- Cysts in the renal sinus may be classified as parapelvic and peripelvic cysts.
- A parapelvic cyst is a renal cortical cyst that herniates into the renal sinus. These cysts are usually large but solitary.
- Peripelvic cysts, in contrast, are lymphatic in origin and usually small and multiple.
24
Q
Hyperdense Cyst
What is it? What likely happened?
How do you diagnose this?
A
- A homogeneous renal cyst with an attenuation of >70 Hounsfield units on noncontrast imaging represents a benign hyperdense cyst, likely secondary to prior hemorrhage.
- A hyperdense cyst cannot be diagnosed if only post-contrast imaging is available as there is no way to distinguish a hyperdense cyst from an enhancing renal mass.
25
Q
Bosniak Classification
What is it?
Which classes have no/small/high risk for malignancy?
A
- The Bosniak classification risk-stratifies cystic renal masses, with increasing risk for cystic renal cell carcinoma with increasing Bosniak category. Classification is based on morphology, not size (except for hyperdense cysts in categories II and IIF).
- Category I and II: No risk of malignancy. No follow-up necessary.
- Category IIF: Small risk of malignancy. Imaging follow-up is needed.
- Category III and IV: Surgical lesions, concerning for cystic renal cell carcinoma.
26
Q
Bosniak Catergory I
A
- Water-attenuation cyst, with a hairline wall and no areas of enhancement.
- Practically, this classification is never used as such a lesion is simply called a simple renal cyst.
- Always benign. No follow-up needed.
27
Q
Bosniak Category II
A
- Water-attenuation cyst containing a few (3 or fewer) hairline septa. May contain fine septal calcification. No enhancement.
- Also includes small (<3 cm) hyperattenuating cysts without enhancement.
- Essentially always benign. No follow-up needed.
28
Q
Bosniak Classification IIF
A
- Multiple septa, with minimal smooth thickening (3 mm or less). may have thick and nodular mural calcification.
- Walls may slightly enhance.
- Also includes large (>3 cm) hyperattenuating cysts without enhancement.
- Usually benign. Radiographic follow-up is recommended, where morphologic change or new enhancement would be concerning for malignancy.
29
Q
Bosniak Category III
A
- Thickened, irregular walls or septa, with measurable enhancement.
- Concern for malignancy, but may be benign (ie infection, multilocular cystic nephroma.)
- Without comorbidities, treatment is surgical.
31
Q
Autosomal Dominant Polycystic Kidney Disease
Approximately responsible for how many patients on long-term dialysis?
Typical presentation?
What is another important association?
Imaging?
RCC association? If so, characteristic presentation?
A
- Autosomal dominant polycystic kidney disease ADPKD is responsible for 10% of patients on long-term dialysis.
- Patients typically present in their third to fourth decades, initially presenting with upper abdominal pain and a clinical course of progressive renal failure. The kidneys may become so enlarged as to be palpable. Hypertension and hematuria (thought to be due nephrolithiasis or rupture of a renal cyst into the collecting system) are common.
- Approximately one-half of patients will have a saccular aneurysm in the circle of Willis.
- On imaging, the kidneys are markedly enlarged and feature multiple cysts of varying attenuation or signal intensities due to hemorrhage.
- The traditional teaching is that ADPKD does not increase the risk of renal cell carcinoma. However, some authors propose that there is a slightly increased risk.
- Renal cell carcinoma associated with ADPKD tends to occur at a younger age and is more often bilateral, multifocal, and sarcomatoid. Diagnosis of renal malignancy is complicated by the presence of multiple (often hemorrhagic) cysts and frequently concomitant renal insufficiency, which may preclude the use of intravenous contrast.
33
Q
Pyelonephritis
What is it? What causes it?
Image findings?
A
- Pyelonephritis is an infection of renal parenchyma and is the most common bacterial infection of the kidney. The bacteria usually are ascending from the bladder.
- The imaging findings of pyelonephritis are nonspecific and imaging may be normal in up to 75%. Various patterns may be seen, including a unilaterally enlarged kidney, wedge-shaped or striated regions of decreased enhancement, and perinephric stranding. The urothelium may also be thickened and hyperenhancing.
- The differential diagnosis of a unilateral enlarged kidney includes pyelonephritis, acute ureteral obstruction, renal vein thrombosis, and compensatory hypertrophy.
- A striated nephrogram describes linear lucencies extending from the renal cortex to the medulla on a contrast-enhanced study. The differential diagnosis for a striated nephrogram is similar to that of a wedge-shaped perfusion defect.
- Focal pyelonephritis (previously called focal lobar nephronia) may mimic a renal mass.
- Mild hydronephrosis can be seen on the affected side, thought to be due to a bacterial endotoxin causing reduced peristalsis, and should not be confused with obstructive uropathy.
36
Q
Emphysematous Pyelonephritis
What is it?
Exclusively seen in what population?
Treatment?
A
- Emphysematous pyelonephritis is a severe renal infection characterized by gas replacing renal parenchyma, caused both by gas-forming organisms and renal infarction.
- Emphysematous pyelonephritis is seen almost exclusively in diabetic patients.
- Emphysematous pyelonephritis is a surgical emergency, requiring emergent nephrectomy.
39
Q
Xanthogranulomatous Pyelonephritis
What is it? What happens to the renal parenchyma?
Two most common causal organisms?
Clinical presentation?
What is “tumefactive XPG”?
Primary imaging modality? Imaging appearance? What is the “bear paw sign?
Primary differential?
Treatment?
A
- Xanthogranulomatous pyelonephritis - XPG is a chronic renal infection due to obstructing calculi, leading to the replacement of renal parenchyma with fibrofatty inflammatory tissue.
- Proteus mirabilis and Escherichia coli are the two most common organisms.
- The clinical presentation of XPG includes flank pain and nonspecific constitutional symptoms, such as fever and weight loss. Anemia and hematuria are also common.
- XPG can be diffuse (85%) or localized. The localized form, also known as “tumefactive XGP,” may mimic a renal mass.
- CT is the primary modality for imaging, which demonstrates fatty replacement of the renal parenchyma, marked perinephric inflammatory standing, and staghorn calculi.
- The bear paw sign represents the configuration of the hypoattenuating fibrofatty masses arranged in a radial pattern, reminiscent of a bear’s paw.
- Primary differential considerations include acute obstructing calculus with pyonephrosis or renal/transitional neoplasm with calcification.
- Treatment is nephrectomy.
40
Q
Renal Tuberculosis
How does the TB get there?
Active pulmonary TB is seen in approximately how many cases of renal TB?
Is it usually bilateral or unilateral?
Image findings? What is a “puddy kidney”?
A
- Mycobacterium tuberculosis infection of the renal parenchyma results from hematogenous dissemination.
- Active pulmonary TB is present in approximately 10%.
- Although initial renal TB infection typically involves both kidneys, chronic changes tend to be unilateral.
- Imaging findings include parenchymal calcification, scarring, papillary necrosis, and infundibular strictures. End-stage renal TB produces autonephrectomy and the characteristic puddy kidney appearance, which represents an atrophic, calcified kidney.
44
Q
Delayed (Prolonged) Nephrogram
What is it?
DDx for unilateral delayed nephrogram
DDx for bilateral delayed nephrogram
A
- A delayed (prolonged) nephrogram describes slow renal parenchymal uptake of intravenous contrast, prolonged enhancement, and delayed urine excretion.
- A unilateral prolonged nephrogram can be due to acute ureteral obstruction, renal vein thrombosis, and renal artery stenosis.
- Bilateral prolonged nephrograms can be seen in bilateral obstruction, contrast nephropathy, systemic hypotension, and myeloma kidney.
45
Q
Medullary Nephrocalcinosis
What is it?
Causes?
A
- Medullary nephrocalcinosis represents calcification of the renal medullary pyramids, usually with preserved renal function. Due to concentrating effects of the loop of Henle, this is 20x more common than cortical nephrocalcinosis.
- Medullary nephrocalcinosis can be caused by:
- Hypercalcemic state (e.g., hyperparathyroidism, sarcoidosis, etc). (this also helps you remember that medullary nephrocalcinosis is 20x more common then cortical nephrocalcinosis)
- Medullary sponge kidney (cystic dilation of distal collecting ducts) may be unilateral or segmental).
- Distal (type 1) RTA.
-
Furosemide therapy in a child.
- Radiopaedia MNEMONIC H: hyperparathyroidism; A: (renal tubular) acidosis; M: medullary sponge kidney; H: hypercalcemia / hypercalciuria; O: oxalosis; P: papillary necrosis
46
Q
Cortical Nephrocalcinosis
What is it?
Causes?
A
- Cortical nephrocalcinosis is dystrophic peripheral calcification of the renal cortex, with sparing of the medullary pyramids.
- Causes of cortical nephrocalcinosis include:
- Acute cortical necrosis.
- Chronic glomerulonephritis.
- Chronic transplant rejection.
- Hyperoxaluria
- Alport syndrome (hereditary nephropathy and deafness)
- Mnemonic (COAG) C: cortical necrosis; O: oxalosis; A: Alport syndrome; G: (chronic) glomerulonephritis
47
Q
Cortical Necrosis
What is it?
What two things may it lead to?
Ischemia may be due to what two things?
Predisposing factors?
A
- Cortical necrosis is a rare form of renal injury from acute ischemic necrosis of the renal cortex.
- Cortical necrosis may lead to cortical nephrocalcinosis.
- Chronic renal failure develops in up to 50% of patients.
- Ischemia may be due to small vessel vasospasm or systemic hypotension.
- Predisposing factors include hemolytic-uremic syndrome and thrombotic microangiopathy.
49
Q
Renal Trauma
What is the most commonly used system for classifying renal trauma?
What are its limitations? Be specific in what it may lack!
What causes traumatic renal artery thrombosis?
What is a pseudoaneurysm? Imaging appearance?
A
- The OIS scale from the AAST is the most commonly used system for classifying renal trauma. It is a surgical classification but correlates well with the CT findings.
- The OIS classification is somewhat limited as there are several important renal injuries, including traumatic renal artery thrombosis, renal artery pseudoaneurysm, and ureteral avulsion (most commonly occurring at the ureteropelvic junction) that are not included in the OIS classification but which can affect prognosis.
- Traumatic renal artery thrombosis is due to tearing of the intima, which initiates thrombosis. There is a permanent loss of renal function after approximately two hours of ischemia.
- Pseudoaneurysm is an arterial injury with a high risk of fatal rupture. On imaging, a pseudoaneurysm will be of similar density to the aorta, with arterial enhancement in the arterial phase and washout on delays. Treatment is endovascular embolization.
52
Q
Transitional Cell Carcinoma
Prevalence?
Typical imaging appearance?
If TCC is diagnosed in the ureter, what else should be evaluated and why?
A
- Although upper-tract malignancy is rare, transitional cell carcinoma is the most common ureteral neoplasm.
- The typical imaging appearance is a single filling defect on CT urography; however, multiple filling defects may be seen in 40%. Less commonly, there may be focal thickening of the ureteral wall. Given the propensity of transitional cell carcinoma for multifocality, the bladder should be evaluated for a synchronous mass.
60
Q
Uretocele
What is it?
What kinds are there?
Describe each kind.
What is a pseudouretocele? Causes?
A
- A ureterocele is a focal dilation of the most distal portion of the ureter that protrudes into the bladder. A ureterocele may be orthotopic or ectopic.
- An orthotopic ureterocele is seen with a normally inserting ureter, and is seen most commonly in adults. Orthotopic ureteroceles are also known as simple, adult-type, and intravesicular ureteroceles. orthotopic ureteroceles are usually asymptomatic.
- Mnemonic: “Older people need ortho”
- An ectopic ureterocele is seen in the setting of a duplicated collecting system, with ectopic insertion of the upper pole ureter into the bladder, and is usually diagnosed in children.
- A pseudoureterocele represents intussusception of the distal ureter into the bladder, which may be due to tumor, radiation cystitis, orureterovesicularjunction stone.
62
Q
Bladder Transitional Cell Carcinoma
Where is the most common site of malignancy?
Seen in what population?
Risk factors?
Presentation?
How does it spread?
Which kind can be treated endoscopically? Which kind needs radical cystectomy?
What portends a poorer prognosis?
A
- Transitional cell carcinoma is by far the most common bladder cancer. The bladder is the most common site of malignancy in the urinary tract.
- TCC is a disease of older adults with a male predominance.
- Risk factors include smoking and aromatic amines.
- It presents with painless hematuria.
- Bladder cancer spreads through the wall of the bladder. Organ-confined disease can be divided into nonmuscle-invasive (70%; typically resected endoscopically) and invasive (25% typically treated with radical cystectomy/nodal dissection).
- Metastatic bladder cancer (5%) is treated with systemic therapy.
- The presence of pelvic lymph nodes portends a poorer prognosis.
- If bladder cancer is clinically suspected, a negative CT urogram does not obviate the need for cystoscopy.
63
Q
Bladder AdenoCA
Prevalence? What is it associated with?
A
- Adenocarcinoma of the bladder is rare but is associated with a urachal remnant.
- The fetal urachus extends from the bladder dome to the umbilicus. It should be obliterated after birth but may persist as a urachal anomaly.
65
Q
Extraperitoneal Bladder Rupture
Definition? Which kind is more common when compared to intraperitoneal class?
More or less associated with pelvic fx when compared to intraperitoneal bladder rupture?
What sign is characteristic?
Treatment?
A
- Extraperitoneal bladder rupture is defined as rupture of the bladder outside of the peritoneal space. Extraperitoneal bladder rupture is at least twice as common as intraperitoneal rupture.
- Extraperitoneal bladder rupture is more commonly associated with pelvic fractures compared to intraperitoneal rupture. Extraperitoneal bladder rupture is typically caused by direct laceration of the bladder by a bone fragment.
- The molar tooth sign describes the characteristic inverted U appearance of extravasated contrast in the extraperitoneal space of Retzius, which mimics a molar tooth.
- Extraperitoneal bladder rupture is typically managed conservatively, by placement of a urinary catheter.
66
Q
Intraperitoneal Bladder Rupture
This occurs when what is disrupted?
Mechanism of injury?
Image finding?
Treatment?
A
- Intraperitoneal bladder rupture occurs with disruption of the bladder dome and peritoneum, causing resultant extravasation of urine into the peritoneal space.
- The mechanism of intraperitoneal bladder rupture is thought to be through pressure forces on a full bladder causing bursting at the dome into the peritoneum.
- The pathognomonic imaging finding on CT cystogram is intraperitoneal contrast interdigitating between loops of bowel.
- Intraperitoneal bladder rupture is typically treated surgically.
67
Q
- Male Urethral Anatomy
- Prostatic Urethra
- Verumontanum
- Prostatic Utricle
- Membranous Urethra
- Bulbous Urethra
- Penile Urethra
- Fossa Navicularis
- Prostatic Urethra
A
- The prostatic urethra courses within the prostate and is lined with transitional epithelium.
- The verumontanum is a prominent ridge of smooth muscle in the posterior portion of the prostatic urethra, and is the site of the paired ejaculatory duct orifices. The verumontanum is also the site of obstruction in posterior urethral valves in children. The prostatic utricle is a Müllerian duct derivative and is the blind-ending male homologue of the uterus and vagina, which is also located at the verumontanum.
- The membranous urethra is the shortest, least mobile urethral segment.
- The membranous urethra is contained within the urogenital diaphragm, which contains the external urethral sphincter and the paired Cowper’s glands. Bulbous urethra (anterior urethra)
- The bulbar urethra is the site of drainage of Cowper’s glands.
- The penile urethra is the longest urethral segment. It is lined with squamous epithelium.
- The distal portion of the penile urethra is dilated at the glans penis. This dilation is called the fossa navicularis.
- The glands of Littré are small mucous glands of the penile urethra. Normally, small ducts would be occluded by balloon during a retrograde urethrogram, and therefore would not opacify with injected contrast. The glands of Littré tend to opacify more prominently when inflamed in the setting of urethritis.
71
Q
Urethral Trauma
In the setting of trauma, when should an RUG be performed?
If the RUG shows evidence of urethral injury, what is typically placed?
What is the most common type of urethral injury? Where would contrast extravasate in this type of injury?
A
- In the setting of trauma, if there is blood at the meatus, painful urination, or inability to void, a RUG should be performed emergently. If the RUG shows evidence of urethral injury, a suprapubic catheter is typically placed.
- There are five types of urethral injury. Type III, pictured, is the most common, with disruption of the urogenital diaphragm and rupture of the bulbomembranous urethra.
- Contrast extravasates both into the pelvis and out into the perineum in a type III injury.
72
Q
Female Urethral Diverticulum
Presentation?
Etiology?
What two things can develop in a urethral diverticulum?
A
- Urethral diverticulum presents clinically with postvoid dribbling, urethral pain, and dyspareunia. often, however, the symptoms may be vague and nonspecific.
- Diverticula are thought to arise from glandular dilation caused by inflammation and chronic infection of the paraurethral glands of Skene.
- Urethral diverticula are prone to develop calculi due to urinary stasis.
- Very rarely, adenocarcinoma may develop within a urethral diverticulum.
