GU 2 -- Renal Masses
Terms
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- How are 50% of renal cell carcinomas diagnosed?
- Incidentally on imaging studies performed for other reasons
- What is true of lesions diagnosed incidentally versus those diagnosed after symptoms are present?
- Most of them are stage T1 or T2, and amenable to surgical treatment
- Why has survival in RCCa improved over the past 40 years?
- Earlier diagnosis directly attributable to imaging
- What is a ball?
- Renal mass that grows circumferentially, expanding the contour of the kidney as it comes into contact with the capsule.
- What is a bean?
- Renal lesion that is infiltrative. May swell the involved area, but the bean shape of the kidney is maintained.
- What masses are in the “ball†category?
- Most common renal masses: Cysts, renal cell CA, angiomyolipoma, oncocytoma, most metastases, and abscess.
- What masses are in the “bean†category?
- The three “Iâ€s.
- What are the three “Iâ€s
-
Infiltrating neoplasms
Inflammatory lesions
Infarction - What are the infiltrating neoplasms?
-
Transitional cell CA
Squamous cell CA
Infiltrating renal cell CA
Renal medullary CA
Lymphoma
Leukemia
Some metastases - What are the common “balls�
-
Cyst
Renal cell carcinoma - What are the uncommon balls?
-
Angiomyolipoma
Abscess
Most metastases - What are the rare balls?
- Oncocytoma, Multilocular cystic nephroma, Focal XGP
- What are the common beans?
- Transitional cell CA, Pyelonephritis
- What are the uncommon beans?
- Squamous cell carcinoma, Infiltrating renal cell carcinoma, Lymphoma, Some metastases, Infarct
- What are the rare beans?
- Renal medullary carcinoma, Collecting duct carcinoma, Leukemia
- What is the sensitivity of US for renal mass?
- 80%
- What is the sensitivity of CT for renal mass?
- Greater than 95%
- Where may a renal mass be first identified?
- Plain film
- What makes a renal mass suspicious?
- Calcification
- What is an old urology adage?
- “A calcified renal mass is a surgical renal massâ€
- What pattern of calcification in the area of the kidney is suspicious on plain film?
- Rim calcification.
- What percent of patients with rim calcification have malignancy?
- 20%
- What are the other 80% due to?
- Rim calcification in renal cysts
- What percent of renal cysts have rim calcification?
- 1%.
- What percent of renal cell CA has calcification?
- 15%
- What percent of renal masses that have calcification visible on plain film are due to renal cell CA?
- 60%
- What are other frequently calcified renal lesions?
- Complex renal cysts, XGP, Hemangiomas, Chronic perirenal hematomas, Aneurysms/vascular malformations
- What is ultrasound particularly crappy at finding?
- Infiltrating renal lesions (beans)
- What are the phases of nephrogram after IV contrast on CT?
- Portal venous phase correlates to corticomedullary phase, 120 seconds correlates to tubular (nephrographic) phase, Delayed imaging is in the equilibrium phase
- When are renal lesions most commonly missed on MDCT?
- When the kidneys are imaged only in the corticomedullary phase
- When is the optimal phase for renal mass detection?
- Tubular/nephrographic phase, when the cortex and medulla are contrast opacified, and contrast is starting to pour into the renal pelvis.
- How will almost all renal tumors appear in this phase?
- Hypodense
- How are all renal lesions classified from the most basic imaging appearance standpoint?
- Expansile versus geographic infiltrating
- How are lesions further classified?
- Solitary versus multiple
- What is seen in 50% of patients over 50?
- Renal cysts
- When is the only time renal cysts are worrisome?
- In a child.
- What may they signal in a child?
- May signal inheritable cystic disease.
- What about in young patients?
- Not uncommon in young adults.
- How is diagnosis of cyst confirmed?
- Ultrasound
- What is acceptable for simple cyst?
- Anechoic, with augmented through transmission and well demarcated back wall.
- What can simple cyst contain?
- 1 or 2 delicate internal septations (of course without flow).
- What should any lesion with any variance from these criteria have done to it?
- Be analyzed with CT to exclude a neoplasm.
- What are Bosniak class I cysts?
- Simple cysts
- What is criteria for Bosniak I?
- Water density mass, No enhancement, Imperceptible or barely perceptible margin
- What are characteristics of Bosniak II renal cystic lesions?
- Multiple (3 or more) septations, Thin peripheral calcification, High density contents
- What other lesion falls into Bosniak II category?
- Cysts with appearance consistent with infection
- What is the suspected cause of the septations, rim calcification, and/or high density contents seen in Bosniak II lesions?
- Prior infection
- What is the “BIRADS†for these lesions?
- Probably benign lesions. Follow up recommended.
- When is the follow-up to be done?
- Repeat CT scanning in 6-12 months to exclude progression of disease.
- What is the most problematic Bosniak II lesion?
- The hyperdense cyst.
- What is the appearance of hyperdense cyst on unenhanced CT?
- Hyperdense relative to renal parenchyma.
- What is appearance of hyperdense cyst on enhanced CT?
- Hypodense relative to renal parenchyma.
- What happens to the cyst in the interval?
- NOTHING. No part of the lesion can enhance, otherwise it is Bosniak IV and is a surgical candidate.
- If a hyperdense cyst is problematic, what can be done for further evaluation?
- Ultrasound, to confirm its nature as a benign cyst.
- What if the lesion cannot be confirmed as simple cystic?
- Short term follow up or surgical removal.
- What are Bosniak class III lesions?
- More complex characteristics than those typically explained by postinfectious sequelae.
- What are the characteristics?
- Dense thick calcification, Numerous septae or loculations, Nodularity of septa(e), Unenhancing solid components
- What is the “BIRADS†of Bosniak III lesions?
- 50% are cystic renal cell carcinoma, 50% are benign
- What are the typical etiologies of the benign Bosniak III lesions?
- Cysts complicated by infection, Cysts complicated by hemorrhage, Multilocular cystic nephroma
- How is presurgical differentiation of benign versus malignant Bosniak III lesions performed?
- It isn’t done. Bosniak III lesions are excised.
- What are characteristics of Bosniak IV lesions?
- Any area of solid enhancing tissue. Irregular margins.
- Where is the enhancing solid tissue typically?
- At the periphery of the cystic lesion.
- How should apparently benign cystic lesions be evaluated on CT?
- With careful attention to the lesion periphery. Any peripheral enhancement, even rim enhancement, is consistent with Bosniak IV lesion.
- What is the presumed diagnosis in a Bosniak IV lesion?
- Cystic renal cell CA.
- What percent of RCCA has cystic areas?
- 20%
- What is true in 75% of these RCCAs with cystic contents?
- The cystic areas represent central necrosis
- What is the largest component of the other 25%?
- Truly cystic RCCAs, which represent the papillary variety of RCCA.
- What is the appearance of papillary RCCA?
- Cystic lesion with frond-like tissue protruding into the cyst from the periphery
- What is true of these lesions?
- Hypovascular
- How is their papillary nature best evaluated?
- Ultrasound
- What is in the rest of the 25%?
- RCCA that occurred adjacent to an already present cyst.
- What can a renal cyst represent?
- It can signal the presence of a renal mass, which it formed by obstructing renal tubules. Thus renal cysts can herald the presence of a RCCA.
- What is the rarest RCCA/cyst combination?
- RCCA that originated in the wall of an already present cyst.
- What is renal cell carcinoma also called?
- Renal adenocarcinoma
- What is the appearance of RCCA on cross sectional imaging?
- Expansile, with solid components
- What excludes RCCA?
- Intratumoral fat.
- What is the exception to this rule?
- If the mass has grown to engulf renal sinus or perirenal fat. This can usually be discerned from true intrinsic tumor fat.
- What is the typical density of RCCA precontrast on CT?
- Isodense
- Is this always true?
- No. Sometimes hypodense. Sometimes hyperdense due to hemorrhage.
- What is the typical density of RCCA postcontrast on CT?
- May be transiently hyperdense during initial bolus. All are hypodense during infusion phase. ? Appearance on delayed images (5 min)—probably mildly enhancing, like with gado.
- What percent of RCCA are expansile?
- 95%
- What percent of RCCA are inflitrative?
- 5%
- What percent of RCCA are calcified on CT?
- 30%
- What percent exhibit transient hyperdensity during bolus?
- 50%
- How often is percutaneous renal biopsy performed?
- Rarely
- What is one of the few indications for percutaneous renal biopsy?
- Patient with renal mass and known primary tumor elsewhere.
- Why?
- AMLs smaller than 4 cm are very unlikely to hemorrhage.
- How do infiltrating RCCAs differ in appearance?
- May not bulge renal contour. Homogeneous internal architecture (like small masslike RCCAs)
- How are infiltrating RCCAs detected?
- Hypodensity versus surrounding parenchyma
- What is a clinical presentation in which RCCA may be the underlying cause, but will not be suspected?
- Renal abscess.
- How does this occur?
- Necrotic center of RCCA becomes infected.
- How are renal abscesses managed?
- 1) Send drainage fluid for cytology. 2) FOLLOW UP IMAGING TO EXCLUDE UNDERLYING MASS
- When is the follow up imaging performed?
- After symptoms have resolved.
- What is another presentation of RCCA in which the diagnosis is often missed?
- Nontraumatic subcapsular/perirenal hemorrhage
- What does nontraumatic subcapsular/perirenal hemorrhage mean until proven otherwise?
- Underlying malignant tumor.
- What percentage of subcapsular/perirenal hemorrhage is due to RCCA?
- 55%
- Why is the underlying diagnosis missed?
- The hemorrhage, which can be extensive, obscures the underlying tumor
- What should be done in all cases of subcapsular or perirenal hemorrhage where a mass is not detected on the initial diagnostic study as the underlying cause?
- Arteriography
- What is being searched for on the arteriogram?
- Vasculitis, vascular malformation, or other vascular lesion to explain the presence of hemorrhage.
- If one is detected, what is done?
- The lesion can be assumed the cause of the bleed.
- What if no such lesion is identified (i.e. normal arteriogram)
- CT or MRI should be repeated to look for an underlying mass.
- When is the repeat study performed?
- 1 Month after the hemorrhage, to allow time for the blood to clear.
- What does the follow up scan often reveal?
- A mass, which may be benign or malignant.
- What benign mass often bleeds?
- Angiomyolipoma.
- How are they treated?
- Nonsurgically or with renal sparing surgery if possible.
- What is the treatment for RCCA?
- Usually nephrectomy
- What is the advantage of this approach?
- Minimize nephrectomy for benign lesions.
- What is the appearance of RCCA on US?
- Solitary expansile mass
- What is the echogenicity?
- Variable. May be hyper, iso, or hypoechoic versus normal renal parenchyma
- What is the sonographic appearance of most small (< 5 centimeter) RCCAs?
- Mildly hyperechoic
- What is sometimes seen?
- Marked hyperechogenicity.
- What lesion is this imaging appearance the same as?
- Angiomyolipoma
- In what percent of <5 cm RCCAs does this appearance occur?
- 15%
- What does this mean?
- You can’t diagnose an AML based on US appearance alone. Must exclude RCCA with CT.
- What should all renal masses detected on US have done to them?
- A CT (or MRI) for further evaluation.
- What percentage of RCCA can be accurately staged on imaging?
- 90%
- What is stage I?
- Tumor confined within renal capsule
- What is stage II?
- Invasion of perirenal fat without lymph node mets
- What is stage III divided into?
- a, b and c
- What is stage IIIa?
- Tumor invasion into renal vein or IVC
- What is stage IIIb?
- Lymph node mets
- What is stage IIIc?
- Renal vein or IVC invasion AND lymph node mets
- What is stage IVa disease?
- DIRECT INVASION of the tumor PAST GEROTA’S FASCIA
- What is stage IVb disease?
- Distant metastases
- What is the best way to diagnose renal vein or IVC tumor invasion?
- High-rate infusion CTA of the renal veins/IVC.
- What is the most reliable finding?
- Thrombus visualized in the vessel.
- What finding is unreliable?
- Enlargement of the renal vein, as it may be enlarged simply secondary to increased flow related to hypervascular RCCA.
- What is the most practical method to confirm tumor thrombus in the renal vein or IVC and determine its extent?
- Ultrasound with doppler
- What size nodes are pathologic?
- 1.5 cm in short axis
- What size nodes are suspicious?
- 1.0 or greater
- What are common sites for distant mets of RCCA?
- Liver, bone, lung, brain
- What must be done to detect RCCA liver mets?
- Unenhanced imaging and ARTERIAL PHASE imaging as they are hypervascular.
- What is the importance in differentiating stage I from stage II?
- No practical importance, as both can be treated with partial nephrectomy.
- What is the most important thing to note in stage II disease?
- Whether the ipsilateral adrenal is involved or not.
- What is the most reliable indicator of perinephric tumor spread?
- Discrete perinephric soft tissue mass.
- What are unreliable signs?
- Perinephric stranding, fat obliteration, or enlarged perinephric vessels
- When should MRI be performed in evaluation of RCCA?
- Only when CT is inadequate for staging.
- What is T1W and T2W appearance of RCCA?
- Variable and unreliable. Just look for contour disrupting mass.
- What is appearance post contrast on MR?
- Hypointense on infusion phase. Mildly hyperdense on delayed imaging (3-5 min).
- What percent enhancement is considered highly suspicious for malignancy?
- 15%
- How is tumor extension into renal vein/IVC detected on MR?
- Absence of flow void on black blood. More sensitively diagnosed with bright blood images as a filling defect, however.
- What is the most important thing to tell surgeon about IVC extension?
- Whether it extends above the hepatic vein inflow.
- What is the most important reason that suspected RCCA is not biopsied for confirmation before excision in surgical cases?
- RCCA can contain elements that appear like oncocytoma.
- What is oncocytoma?
- Benign renal tumor with no metastatic potential
- What are the diagnostic imaging findings of an oncocytoma?
- There are none.
- How is the diagnosis made preoperatively?
- It is NOT made preoperatively, because as mentioned before, even if the pathology comes back as oncocytoma, this STILL does not rule out RCCA, because RCCA can contain elements resembling oncocytoma.
- What is the best thing that suggesting a diagnosis of oncocytoma can do for a patient/surgeon?
- Can suggest that the lesion may be benign, and a renal sparing approach may be considered.
- How does the surgeon decide whether to do renal sparing or more aggressive surgery?
- Based on frozen section biopsies taken intraoperatively.
- What are the typical features of oncocytoma on CT or MR?
- Well circumscribed. Homogeneous enhancement. Central stellate scar.
- What may be seen around the edge of the lesion?
- A pseudocapsule.
- What is a pseudocapsule?
- Normal renal tissue compressed around the lesion.
- What is the ultrasound echogenicity?
- Isoechoic to renal parenchyma.
- What do oncocytomas that exceed 6 cm often contain?
- Central areas of necrosis.
- What is the angiographic appearance of oncocytoma?
- Spoke-wheel pattern.
- What is spoke wheel pattern?
- There is a prominent rim of vessels at the periphery of the lesion, with (somewhat difficult to visualize) centrally radiating vessels.
- When a multilocular cystic nephroma is suspected by imaging, how is the surgical approach handled differently?
- If the patient is in the first peak (boys under 3 y.o.), I am not sure how it is handled.
- What if the multicystic tumor is seen herniating into the renal pelvis?
- Consistent with MLCN, but still not good enough to exclude RCCA.
- What percentage of MLCN hemorrage?
- They do not hemorrhage. If hemorrhage is seen in a multicystic mass, it is another diagnosis, probably RCCA.
- What is the DDx for a multiloculated cystic renal mass?
- Cystic RCCA Cystic Wilms Multilocular cystic nephroma Segmental multicystic dysplastic kidney Localized renal cystic disease Renal abscess Rare forms of renal inflammatory disease (echinococcus, segmental XGP, renal malakoplakia)
- Of these lesions, which is the most common when a multicystic renal mass is identified?
- RCCA.
- What is segmental multicystic dysplastic kidney?
- MCDK involving only part of the kidney.
- Where is it seen?
- Only in cases of renal duplication.
- What suggests it?
- Presence of duplication with unenhancing solid components.
- What is localized renal cystic disease?
- Rare disease of a collection of simple cysts in one part of one kidney. They look like individual cysts that just happen to be close together. They have normal enhancing renal tissue between them.
- What is the usual cause of renal abscess?
- Untreated or improperly treated pyelonephritis.
- What is the clinical setting of renal abscess?
- Persistent infection symptoms despite antibiotic treatment (i.e. at least 72 hours after treatment commencement)
- What confirms the diagnosis of renal abscess in the right clinical setting?
- Gas
- What is the enhancement pattern?
- Peripheral enhancement
- What is the treament for renal abscess?
- IV Abx and percutaneous drainage.
- What else must be treated if present?
- Ureteral obstruction.
- Why must this be treated?
- Ureteral obstruction impairs blood flow and limits antibiotic delivery to the parenchyma.
- What is the clinical history with focal XGP?
- Recurrent UTI
- In what demographic group?
- Middle aged women
- What is the appearance?
- Nonspecific. See nonfunctional mass which may exhibit minimal contrast enhancement. Usually perinephric stranding.
- What is seen in 80% of cases of focal XGP?
- Calculus.
- What are the common causes of multilocular cystic renal masses?
- RCCA Septated renal cyst Renal abscess
- What are the uncommon causes of multilocular cystic mass?
- Multilocular cystic nephroma Cystic Wilms Segmental multicystic dysplastic kidney
- What are the rare causes of multilocular cystic mass?
- Focal XGP Localized renal cystic disease Echinococcus Malakoplakia AVM or AV fistula
- In a patient with known extrarenal malignancy, what is the differential diagnosis of a solitary renal mass?
- Renal metastasis RCCA
- How is the diagnosis made?
- This is the one time percutaneous biopsy is indicated, as it dictates whether patient has surgical disease or not.
- What tumors metastasize to kidney commonly?
- Breast. Lung GI Malignant melanoma
- What other lesion commonly metastasizes to the kidney?
- Lymphoma
- In what percent of patients with lymphoma is there renal involvement?
- 1/20 (5%).
- What is special about these patients?
- They usually have known lymphoma, and they usually have extensive disease, which secondarily involves the kidney.
- What is true about primary renal lymphoma?
- Exceedingly rare.
- What is the characteristic pattern of lymphoma (i.e. not always seen, but when seen suggestive of it)?
- Extensive retroperitoneal mass, which spreads directly into the renal sinus, OR into the perinephric space, encasing the kidney. These features are IN ADDITION to its parenchymal involvement of the kidney.
- How many patterns of renal parenchymal involvement in lymphoma are there?
- 3
- What is the most common pattern?
- Multiple homogeneous nodules
- What is the parenchymal displacement pattern?
- Infiltrating, not exerting mass effect
- What is the second most common pattern of renal parenchymal involvement in lymphoma?
- Diffuse infiltration.
- What is this pattern usually typified by?
- Bilateral involvement. Renal enlargement, sometimes massive, with loss of renal architecture
- What occurs functionally?
- Decreased function
- In what condition is this pattern seen even more commonly than in lymphoma?
- Leukemia
- What is the least common parenchymal involvement pattern in lymphoma?
- Solitary lesion
- What does this pattern mimic?
- RCCA
- What would be useful if this pattern is seen in a patient with known lymphoma?
- Percutaneous biopsy, as lymphoma is not a surgical lesion
- With all patterns of involvement, what are the common features of the parenchymal lesions?
- Homogeneous Minimal enhancement (hypodense versus normal renal parenchyma)
- What is the appearance of lymphoma on ultrasound?
- Since lymphoma is from a monoclonal line of cells which are densely packed, there is little internal echo generation, and lesions appear hypoechoic to anechoic.
- What differentiates this from cyst?
- No significant posterior acoustic augmentation.
- When a focal renal mass is present, RCC is the most likely diagnosis. What additional finding suggests that the lesion is not RCC?
- Marked retroperitoneal lymphadenopathy, which would suggest lymphoma.
- What is important about angiomyolipoma and imaging of it?
- It is one of the few renal masses that can be definitively diagnosed by imaging
- In what group of patients do most angiomyolipomas occur?
- Middle age
- Is there a sex predilection?
- Females
- What is characteristic of lesions in these patients?
- Small, asymptomatic
- A significant percentage of angiomyolipomas occur in another demographic group. Which?
- Patients with tuberous sclerosis
- What percentage of patients with angiomyolipoma have tuberous sclerosis?
- 20%
- What percentage of patients with tuberous sclerosis will develop angiomyolipoma?
- 80%
- What are the characteristic features of angiomyolipoma in tuberous sclerosis patients?
-
Multiple tumors
Bilateral invovement
Large symptomatic lesions - When do AMLs occur in patients with TS?
- Detectable before patient reaches 30, in most cases, which is much younger than patients in the general population who get AMLs.
- What is an angiomyolipoma?
- A renal hamartoma. A totally benign lesion.
- What is angiomyolipoma pathologically?
- A lesion composed of varying proportions of angioid, myoid, and lipoid components.
- What occurs in AMLs with a higher proportion of angioid component?
- They are hypervascular, and due to this, some of the feeding arteries develop small aneurysms.
- What do these aneurysms do?
- Predispose to spontaneous hemorrhage.
- What is important about AML hemorrhages?
- Can be massive and life threatening.
- Otherwise, what symptoms do AMLs cause?
- Just those related to mass effect.
- How are AMLs treated?
- Depends on their size.
- What is the size cutoff for treatment?
- 4 cm
- How are these smaller AMLs managed?
- F/U sonogram every 6-12 months.
- What is the treatment for AMLs over 4 cm?
- Embolization or renal sparing surgery.
- What if the lesion is not amenable to renal sparing surgery or embolization?
- Sonographic follow-up evaluation can be used to look for enlargement or other features that would necessitate nephrectomy.
- What are the diagnostic criteria for AML?
- Only one criteria: Fat within a mass arising in the kidney.
- What is one additional unnecessary but nevertheless supporting finding for diagnosing AML?
- Enlarged or aneurysmal vessels within the tumor
- What if you are unsure of intratumoral fat?
-
Do thinner sections
OR
Do CT pixel mapping
OR
Do MRI - How is the diagnosis made with pixel mapping?
- Three contigous pixels between -20 and -100
- How is the diagnosis made on MRI?
- Do T1W imaging with and without fat saturation; should see bright signal on T1W and dark on T1W with fat saturation.
- What is true of 10% of AMLs?
- Contain minimal fat, so that definitive diagnosis cannot be made on imaging. These lesions will appear to be RCCAs, and will be treated as such.
- What are rare findings that can occur with AML?
-
Tumor extension into renal vein/IVC
Lymph node spread - What is the differential diagnosis for common causes of multiple renal masses?
-
1) Simple cysts
2) Autosomal dominant polycystic kidney disease
3) Acquired cystic disease of dialysis - What is the differential diagnosis for uncommon causes of multiple renal masses?
-
1) Von Hippel-Lindau
2) Tuberous sclerosis
3) RCCA
4) Lymphoma
5) Mets - What is the differential diagnosis for rare causes of multiple renal masses?
-
1) Medullary cystic disease
2) Multiple oncocytomas
3) Multiple abscesses - When do patients with ADPCKD present?
- 20s to 30s
- What do they present with?
- Flank pain, hematuria, urolithiasis, pyelonephritis, renal insufficiency, or HTN
- Where are the cysts anatomically?
- Can develop anywhere along the nephron
- What is the best way to diagnose ADPCKD?
- CT
- What does ADPCKD have genetically?
- High penetrance
- Meaning?
- All patients with the genetic abnormality will develop clinical symptoms.
- How is it inherited?
- Autosomal dominant
- So?
- So a parent with ADPCKD can expect that half of his/her children will develop the disease.
- What is the typical appearance?
- Bilateral renal enlargement due to parenchymal replacement with large number of renal cysts
- What is the increased risk of malignancy in ADPCKD?
- No increased risk
- What do 50% of patients with ADPCKD have in addition to renal findings?
- Liver cysts
- What do 15% of patients with ADPCKD have?
- Berry aneurysyms of the CNS
- Where are other places that cysts can occur in ADPCKD?
-
Adnexa
Pancreas
Spleen
Lung - What other condition do patients with ADPCKD have increased risk for?
- Heart disease
- What types of heart disease?
-
Valvular disease
Aortic coarctation - What are suggests ADPCKD in patients with a parent with the disease?
- Depends if under 30, 30-60, or 60+ years old