Imaging of Small Renal Masses

Mark E. Lockhart, MD, MPHMark E. Lockhart, MD, MPH

University of Alabama at BirminghamUniversity of Alabama at Birmingham

July 28, 2012July 28, 2012

Objectives

Discuss basic imaging findings Discuss basic imaging findings associated with small renal massesassociated with small renal masses

Highlight recent radiology Highlight recent radiology recommendations of incidental renal recommendations of incidental renal lesionslesions

Konnak JW, J of Uro 1985; Ozen H, Br J Uro 1993

Renal “Masses”

Most are now incidental on US, CT and Most are now incidental on US, CT and MRIMRI

Most are simple cysts and require no actionMost are simple cysts and require no action Incidental RCC have lower stage of Incidental RCC have lower stage of

malignancy (82% stage 1) than malignancy (82% stage 1) than symptomatic (37%)symptomatic (37%)

Column of Bertin

Actually a septum Actually a septum rather than a columnrather than a column

Junction of interpolar Junction of interpolar region and poleregion and pole

May be slightly May be slightly echogenic relative to echogenic relative to adjacent cortexadjacent cortex

How to evaluate a renal mass

Is it fatty?Is it fatty?Gross fat is less than -20 HUGross fat is less than -20 HUConsider angiomyolipoma or liposarcomaConsider angiomyolipoma or liposarcoma

Is it cystic?Is it cystic?Is it fluid density (-10 to 20 HU)Is it fluid density (-10 to 20 HU)Use Bosniak criteriaUse Bosniak criteria

Does it enhance?Does it enhance?Borderline is 15-20 HU changeBorderline is 15-20 HU changeMetastases, IVC clot, lymphadenopathy?Metastases, IVC clot, lymphadenopathy?

Angiomyolipoma

10% of patients 10% of patients with tuberous with tuberous sclerosissclerosis

80% of TS have 80% of TS have AMLAML

If exophytic then If exophytic then look for wedge of look for wedge of fat in cortexfat in cortex

Bosniak MA, Rad 1986 Curry NS, AJR 2000

Bosniak Classification

Bosniak MA.Bosniak MA. The current radiological approach to renal The current radiological approach to renal cysts. Radiology 1986;158:1 -10cysts. Radiology 1986;158:1 -10

Type 1 – simple cystType 1 – simple cyst Type 2 – mildly complex; likely benignType 2 – mildly complex; likely benign Type 3 – complex; worrisomeType 3 – complex; worrisome Type 4 – cystic neoplasmType 4 – cystic neoplasm

Cannot show Cannot show enhancementenhancement

Evaluation for Evaluation for de-enhancement de-enhancement can be useful if can be useful if same scanner on same scanner on same daysame day

Bosniak II: Small hyperdense

Bosniak IIF

Slightly more complex cysts that cannot be Slightly more complex cysts that cannot be neatly classified as category II or III neatly classified as category II or III lesions.lesions.

Perceived but Perceived but nonmeasureable nonmeasureable septal enhancement septal enhancement

stable on f/u

Curry NS, AJR 2000; Berland 2012

Bosniak III

Indeterminate cystic massesIndeterminate cystic masses Thickened irregular walls or septa with Thickened irregular walls or septa with

measureable enhancementmeasureable enhancement 25-59% chance malignancy 25-59% chance malignancy Recent work at UAB suggests lower rateRecent work at UAB suggests lower rate Percutaneous biopsy is controversialPercutaneous biopsy is controversial

Bosniak MA, Rad 1986 Curry NS, AJR 2000

Bosniak IV

Malignant cystic masses. Malignant cystic masses. 80-100% likelihood of malignancy80-100% likelihood of malignancy Findings similar to Bosniak III but also Findings similar to Bosniak III but also

have enhancing soft-tissue components have enhancing soft-tissue components adjacent to, but independent of, the wall or adjacent to, but independent of, the wall or septum. septum.

Bosniak IV: Thick enhance septa

Multilocular cystic Multilocular cystic nephromanephroma

Look for extension Look for extension into collecting into collecting systemsystem

No venous extensionNo venous extension

Renal Cell Carcinoma

Most common renal malignancyMost common renal malignancy More common in malesMore common in males Arises in renal cortex – often disrupts renal Arises in renal cortex – often disrupts renal

contour even when smallcontour even when small Bilateral in only 2%Bilateral in only 2% Calcifications in 25-30%Calcifications in 25-30%

Oncocytoma mimics RCC

Both are solid and Both are solid and disrupt cortical margindisrupt cortical margin

Both can enhanceBoth can enhance

Both can have central Both can have central scarscar

Urothelial Carcinoma Central renal mass Central renal mass

with mild ehancementwith mild ehancement

Rarely calcifiedRarely calcified

Extension into Extension into collecting systemcollecting system

Nodal metastasesNodal metastases

Lipid-Poor AML

Mildly hyperdense on Mildly hyperdense on CTCT

Low T2 signal. Does Low T2 signal. Does not drop signal on not drop signal on opposed phase MRIopposed phase MRI

Enhances similar to Enhances similar to RCCRCC

Renal Lymphoma

Focal mass(es)Focal mass(es) Infiltrative massInfiltrative mass Renal hilar massRenal hilar mass Perinephric rindPerinephric rind

Rarely only site Rarely only site of involvementof involvement

Management

ACR white paper on incidental renal massesACR white paper on incidental renal masses Cystic based on Bosniak criteriaCystic based on Bosniak criteria Solid based on sizeSolid based on size

>3cm, surgery>3cm, surgery1-3cm, surgery (may biopsy if 1-3cm, surgery (may biopsy if

hyperdense, homogenously enhancing)hyperdense, homogenously enhancing)<1cm, observe until 1cm<1cm, observe until 1cm

Berland JACR 2010

Management

Slight different criteria if high risk patient or Slight different criteria if high risk patient or limited life expectancylimited life expectancy

Small mass more likely benignSmall mass more likely benign Still rare risk of metastases in small massStill rare risk of metastases in small mass

Lack of morphologic change over 5 years Lack of morphologic change over 5 years suggests benignsuggests benign

Berland JACR 2010

Management different for VHL

Lower malignant potential

Resect when largest 3 cm

Acquired Cystic Renal Disease

Much higher risk of Much higher risk of RCC developmentRCC development

Consider any solid Consider any solid mass as suspiciousmass as suspicious

Summary

Small renal masses are a common Small renal masses are a common diagnostic challengediagnostic challenge

A few have characteristic features that can A few have characteristic features that can help the diagnosishelp the diagnosis

Know the imaging criteriaKnow the imaging criteria