radiologic evaluation of renal cysts

Eugene K. Cha, HMS IIIGillian Lieberman, MD

Radiologic Evaluation of Radiologic Evaluation of Renal CystsRenal Cysts

Eugene K. Cha, Harvard Medical School IIIEugene K. Cha, Harvard Medical School IIIGillian Lieberman, MDGillian Lieberman, MD

November 2004

Eugene K. Cha, HMS3Gillian Lieberman, MD

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Renal AnatomyRenal Anatomy

Netter FH. Atlas of Human Anatomy, Second Edition. 2001, p 313.


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Patient #1: MMPatient #1: MMHPI: 50 HPI: 50 yoyo M M p/wp/w::–– 7 d of flank/back pain7 d of flank/back pain–– 2 d of atypical chest pain2 d of atypical chest pain–– MM MM r/or/o for MI, for MI, r/or/o aortic dissectionaortic dissectionHD #3: MM developed acute LHD #3: MM developed acute L--sided flank sided flank painpainInitial Flank Pain Radiologic Workup: Initial Flank Pain Radiologic Workup: supine and upright plain films of abdomensupine and upright plain films of abdomen


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Patient MM: KUBPatient MM: KUB

PACS, BIDMC

Paucity of bowel gas on left; suggestion of soft-tissue mass


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Menu of Imaging Tests for Renal MassesMenu of Imaging Tests for Renal MassesExcretory Excretory UrographyUrography / Intravenous / Intravenous PyelogramPyelogram (IVP)(IVP)–– Limited sensitivity for small renal massesLimited sensitivity for small renal masses

67% for RCC 3 cm or less67% for RCC 3 cm or lessUSUS–– Reliable identification of simple renal cystsReliable identification of simple renal cysts

(most renal masses)(most renal masses)–– InexpensiveInexpensive

CTCT–– Current gold standard for evaluation of renal massesCurrent gold standard for evaluation of renal masses

MRMR–– For patients with contrast allergyFor patients with contrast allergy–– Elevated serum Elevated serum creatininecreatinine levellevel–– HyperdenseHyperdense renal cystrenal cyst

Amendola MA et al. Small renal cell carcinomas: resolving a diagnostic dilemma. Radiology 1988; 166:637.

Wolf JS Jr. Evaluation and management of solid and cystic renal masses. J Urol 1998 Apr;159(4):1120-33.

Israel GM, Hindman N, Bosniak MA. Evaluation of cystic renal masses: comparison of CT and MR imaging by using the Bosniak classification system. Radiology 2004 May;231(2):365-71.


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Patient MM: Further Radiologic WorkupPatient MM: Further Radiologic Workup

Next, Patient MM had a nonNext, Patient MM had a non--contrast CT contrast CT evaluation of his abdomenevaluation of his abdomen–– NonNon--contrast (noncontrast (non--ideal) because of patientideal) because of patient’’s s

compromised renal functioncompromised renal function


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Patient MM: NonPatient MM: Non--contrast CT Abdomen #1 contrast CT Abdomen #1 (Axial Images)(Axial Images)

well-circumscribed, low-attenuation lesion = liver cyst

well-circumscribed, high-attenuation lesion in kidney low-attenuation

lesions in kidneysPACS, BIDMC


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Patient MM: NonPatient MM: Non--contrast CT Abdomen #2 contrast CT Abdomen #2 (Axial Image and (Axial Image and SagittalSagittal Reconstruction)Reconstruction)

cyst in kidney, calcification

perinephric hematoma w/ adjacent strandingPACS, BIDMC


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Patient MM: NonPatient MM: Non--contrast CT Abdomen #3contrast CT Abdomen #3 (Coronal Reconstructions)(Coronal Reconstructions)

perinephric hematoma w/ adjacent stranding

liver cysts

PACS, BIDMC


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Patient MM: Renal US #1 (Transverse R)Patient MM: Renal US #1 (Transverse R)

PACS, BIDMC

cyst


1111

Patient MM: Renal US #2 (Patient MM: Renal US #2 (SagittalSagittal R)R)

PACS, BIDMC

Enlarged right kidney


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Patient MMPatient MMPMH:PMH:–– Adult polycystic kidney diseaseAdult polycystic kidney disease–– Chronic renal failureChronic renal failure–– HTNHTN–– HyperlipidemiaHyperlipidemia–– AtrialAtrial fibrillationfibrillation

Diagnosis:Diagnosis:–– Complication of PCKD w/ acute left kidney Complication of PCKD w/ acute left kidney

subcapsularsubcapsular hemorrhagehemorrhage into into perinephricperinephric spacespace


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BosniakBosniak Classification: Cystic Renal MassesClassification: Cystic Renal Masses

Category I: simple benign cystsCategory I: simple benign cystsCategory II: minimally complicated cystsCategory II: minimally complicated cystsCategory IIF: minimally complicated cysts that Category IIF: minimally complicated cysts that require radiologic followrequire radiologic follow--upup–– FollowFollow--up in 3 months, then 6 months, then 1 yearup in 3 months, then 6 months, then 1 year

Category III: moderately complicated cystsCategory III: moderately complicated cysts–– Exhibit some radiologic features seen in malignancyExhibit some radiologic features seen in malignancy–– Need surgical explorationNeed surgical exploration

Category IV: clearly malignant cystic carcinomasCategory IV: clearly malignant cystic carcinomasBosniak MA. The current radiological approach to renal cysts. Radiology 1986 Jan;158(1):1-10.

Bosniak MA. Problems in the radiologic diagnosis of renal parenchymal tumors. Urol Clin North Am 1993; 20:217-230.


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Features of Features of BosniakBosniak Category ICategory IBosniakBosniak Category I = simple benign cystsCategory I = simple benign cystsUSUS–– Sharply Sharply marginatedmarginated, smooth walls, smooth walls–– AnechoicAnechoic–– Good through transmissionGood through transmission

CTCT–– Sharp Sharp marginationmargination and demarcation from surrounding and demarcation from surrounding

renal parenchymarenal parenchyma–– Smooth, thin wallSmooth, thin wall–– Water density content, homogeneous throughoutWater density content, homogeneous throughout

(0(0--20 HU)20 HU)–– No enhancement following IV contrastNo enhancement following IV contrast

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


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Review of Patient MM: Renal US #1Review of Patient MM: Renal US #1

Cyst demonstrates:Cyst demonstrates:–– Sharply Sharply marginatedmarginated, thin walls, thin walls–– AnechoicAnechoic–– Good through transmissionGood through transmission

Category ICategory I

PACS, BIDMC


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Complications of Simple CystsComplications of Simple CystsSimple Cysts complicated by:Simple Cysts complicated by:–– HemorrhageHemorrhage–– InfectionInfection–– InflammationInflammation–– IschemiaIschemia

Host response:Host response:–– Inflammatory cellsInflammatory cells–– Granulation tissueGranulation tissue–– NeovascularityNeovascularity

Complicated Cysts:Complicated Cysts:–– CalcificationCalcification–– HemorrhageHemorrhage–– SeptationsSeptations–– Wall ThickeningWall Thickening–– NodularityNodularity at Gross Inspectionat Gross Inspection


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CT Criteria for CT Criteria for BosniakBosniak ClassificationClassification

CriteriaCriteria Cat ICat I Cat IICat II Cat IIFCat IIF Cat IIICat III Cat IVCat IV

WallWall ThinThin ThinThin More than More than thinthin

Thick or Thick or nodularnodular

SeptationsSeptations NoneNone Few, thinFew, thin More than More than few, thinfew, thin

Numerous, Numerous, thickthick

CalcificationsCalcifications NoneNone Few, thinFew, thin More than More than few, thinfew, thin

CoarseCoarse

Density Density prepre--contrastcontrast

00--20 HU20 HU 00--20 HU20 HU 00--20 HU20 HU(except (except

hyperdensehyperdense cyst)cyst)

00--20 HU20 HU > 20 HU> 20 HU

EnhancementEnhancement NoNo NoNo NoNo NoNo YesYes


Bosniak MA. Problems in the radiologic diagnosis of renal parenchymal tumors. Urol Clin North Am 1993; 20:217-230.

Wolf JS Jr. Evaluation and management of solid and cystic renal masses. J Urol 1998 Apr;159(4):1120-33.


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Review of Patient MM: CT #2Review of Patient MM: CT #2Cyst characteristics:Cyst characteristics:–– Thin wallThin wall–– Few, thin Few, thin septationsseptations–– Few, thin calcificationsFew, thin calcifications–– Density: 15 HUDensity: 15 HU

Category IICategory II

PACS, BIDMC


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Patient #2: JD, Patient #2: JD, BosniakBosniak Category IIICategory IIIUS:US:–– Complicated cystic lesion with Complicated cystic lesion with

some solidsome solid--appearing elements appearing elements among cystic spacesamong cystic spaces

CT:CT:–– Multiple Multiple septationsseptations–– Wall: moderate thicknessWall: moderate thickness–– Minimal enhancementMinimal enhancement

Category IIICategory IIINephrectomyNephrectomy: RCC: RCC



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Differential Differential DxDx of Renal Masses and Cystsof Renal Masses and CystsSimple Cyst (Simple Cyst (BosniakBosniak Cat. 1)Cat. 1)Other Probable Benign CystsOther Probable Benign Cysts–– Infected cyst, minimally complicated cyst, Infected cyst, minimally complicated cyst, hyperdensehyperdense cyst cyst

((BosniakBosniak Cat. 2), polycystic kidney diseaseCat. 2), polycystic kidney diseaseCystic Masses Possibly Assoc. w/ MalignancyCystic Masses Possibly Assoc. w/ Malignancy–– vonvon--HippelHippel--LindauLindau, tuberous sclerosis, acquired cystic disease, , tuberous sclerosis, acquired cystic disease,

multilocularmultilocular cystic cystic nephromanephroma, (, (BosniakBosniak Cat. 3 and 4)Cat. 3 and 4)Definable Benign Solid MassesDefinable Benign Solid Masses–– AngiomyolipomaAngiomyolipoma, hematoma, renal anomaly, infarction, lobar , hematoma, renal anomaly, infarction, lobar

nephronianephronia, , xanthogranulomatousxanthogranulomatous pyelonephritispyelonephritisProbable Malignant Solid MassesProbable Malignant Solid Masses–– RCC, transitional cell carcinoma, metastases, lymphoma, RCC, transitional cell carcinoma, metastases, lymphoma,

oncocytomaoncocytoma, etc., etc.Wolf JS Jr. Evaluation and management of solid and cystic renal masses. J Urol 1998 Apr;159(4):1120-33.

Hartman DS. Overview of renal cystic disease: IN: Pollack HM, McClennan BL (eds): Clinical Urography. Philadelphia: WB Saunders, 2000, pp 1245-1250.


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BosniakBosniak Classification SystemClassification SystemIdentifies:Identifies:–– Lesions that do not require further workLesions that do not require further work--upup

Category ICategory ICategory IICategory II

–– Lesions requiring radiologic followLesions requiring radiologic follow--upupCategory IIFCategory IIF

–– Lesions requiring invasive / surgical workLesions requiring invasive / surgical work--upupCategory IIICategory IIICategory IVCategory IV


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Utility of Utility of BosniakBosniak Classification SystemClassification SystemAronson et al. (1991)Aronson et al. (1991)–– Retrospective review of CT/US findings in 16 Retrospective review of CT/US findings in 16

pathologically proven renal cystic massespathologically proven renal cystic massesCat. II lesions: All benign (4/4)Cat. II lesions: All benign (4/4)Cat. III lesions: 3/7 benign, 4/7 malignantCat. III lesions: 3/7 benign, 4/7 malignantCat. IV lesions: All malignant (5/5)Cat. IV lesions: All malignant (5/5)

Aronson S et al. Cystic renal masses: usefulness of the Bosniak classification. Urol Radiol 1991; 13(2):83-90.

Bosniak MA. Difficulties in classifying cystic lesions of the kidney. Urol Radiol 1991;13(2):91-3.


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Utility of Utility of BosniakBosniak Classification SystemClassification SystemWilson et al. (1996)Wilson et al. (1996)–– Retrospective review of CT scans for 20 pts, Retrospective review of CT scans for 20 pts,

24 cystic renal masses biopsied or surgically 24 cystic renal masses biopsied or surgically removedremoved

Cat. I: All benign (7/7)Cat. I: All benign (7/7)Cat. II: 1/5 benign, 4/5 malignantCat. II: 1/5 benign, 4/5 malignantCat. III: All malignant (4/4)Cat. III: All malignant (4/4)Cat. IV: All malignant (6/6)Cat. IV: All malignant (6/6)

Wilson TE, Doelle EA, Cohan RH, Wojno K, Korobkin M. Cystic renal masses: a reevaluation of the usefulness of the Bosniak classification system. Acad Radiol 1996 Jul;3(7):564-70.


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Utility of Utility of BosniakBosniak Classification SystemClassification SystemCurry et al. (2000)Curry et al. (2000)–– TwoTwo--center, prospective and retrospective center, prospective and retrospective

analysis of analysis of properly performedproperly performed renal CT renal CT scans of 109 pts, 116 renal cystic lesionsscans of 109 pts, 116 renal cystic lesions

Cat. I and Cat. II: All benign (15/15)Cat. I and Cat. II: All benign (15/15)Cat. III: 29/49 malignantCat. III: 29/49 malignantCat. IV: All malignant (18/18)Cat. IV: All malignant (18/18)Prospectively followed patients: no malignanciesProspectively followed patients: no malignancies

Curry NS, Cochran ST, Bissada NK. Cystic renal masses: accurate Bosniak classification requires adequate renal CT. AJR Am J Roentgenol 2000 Aug;175(2):339-42.


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BosniakBosniak Classification System: SummaryClassification System: SummaryStudyStudy Malignant LesionsMalignant Lesions

Cat. ICat. I Cat. IICat. II Cat. IIICat. III Cat. IVCat. IV TotalTotal

Aronson et al.Aronson et al. 0/00/0 0/40/4 5/95/9 7/77/7 2020Brown et al.Brown et al. 0/20/2 0/40/4 3/123/12 4/64/6 2424Wilson et al.Wilson et al. 0/70/7 4/54/5 4/44/4 6/66/6 2222

CloixCloix et al.et al. 1/21/2 1/71/7 4/134/13 8/108/10 3232Siegel et al.Siegel et al. 0/220/22 1/81/8 5/115/11 26/2926/29 7070Curry et al.Curry et al. 0/40/4 0/110/11 29/4929/49 18/1818/18 8282

TotalTotal 1/37 1/37 (2.7%)(2.7%)

6/39 6/39 (15.4%)(15.4%)

50/98 50/98 (51.0%)(51.0%)

69/76 69/76 (90.8%)(90.8%)

250250

Curry NS, Cochran ST, Bissada NK. Cystic renal masses: accurate Bosniak classification requires adequate renal CT. AJR Am J Roentgenol 2000 Aug;175(2):339-42.


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ConclusionsConclusionsRenal cysts are commonly found on routine Renal cysts are commonly found on routine imagingimagingBy evaluating morphology, wall thickness, By evaluating morphology, wall thickness, calcification, cyst attenuation, calcification, cyst attenuation, septationsseptations, and , and enhancement, it is possible to identify:enhancement, it is possible to identify:–– Lesions that are benignLesions that are benign–– Lesions that should be managed with radiologic Lesions that should be managed with radiologic

followfollow--upup–– Lesions that require biopsy or surgical excisionLesions that require biopsy or surgical excision


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ReferencesReferencesAmendolaAmendola MA et al. Small renal cell carcinomas: resolving a diagnostic dMA et al. Small renal cell carcinomas: resolving a diagnostic dilemma. ilemma. RadiologyRadiology 1988; 166:637.1988; 166:637.Aronson S et al. Cystic renal masses: usefulness of the Aronson S et al. Cystic renal masses: usefulness of the BosniakBosniak classification. classification. UrolUrol RadiolRadiol 1991; 1991; 13(2):8313(2):83--90.90.BosniakBosniak MA. The current radiological approach to renal cysts. MA. The current radiological approach to renal cysts. RadiologyRadiology 1986 Jan;158(1):11986 Jan;158(1):1--10.10.BosniakBosniak MA. Difficulties in classifying cystic lesions of the kidney. MA. Difficulties in classifying cystic lesions of the kidney. UrolUrol RadiolRadiol 1991;13(2):911991;13(2):91--3.3.BosniakBosniak MA. Problems in the radiologic diagnosis of renal MA. Problems in the radiologic diagnosis of renal parenchymalparenchymal tumors. tumors. UrolUrol ClinClin North North AmAm 1993; 20:2171993; 20:217--230.230.Curry NS, Cochran ST, Curry NS, Cochran ST, BissadaBissada NK. Cystic renal masses: accurate NK. Cystic renal masses: accurate BosniakBosniak classification requires classification requires adequate renal CT. adequate renal CT. AJR Am J RoentgenolAJR Am J Roentgenol 2000 Aug;175(2):3392000 Aug;175(2):339--42.42.HarisinghaniHarisinghani MG, Maher MM, MG, Maher MM, GervaisGervais DA, McGovern F, Hahn P, DA, McGovern F, Hahn P, JhaveriJhaveri K, Varghese J, Mueller K, Varghese J, Mueller PR. Incidence of malignancy in complex cystic renal masses (PR. Incidence of malignancy in complex cystic renal masses (BosniakBosniak category III): should category III): should imagingimaging--guided biopsy precede surgery? guided biopsy precede surgery? AJR Am J RoentgenolAJR Am J Roentgenol 2003 Mar;180(3):7552003 Mar;180(3):755--8.8.Hartman DS. Overview of renal cystic disease: IN: Pollack HM, McHartman DS. Overview of renal cystic disease: IN: Pollack HM, McClennan BL (eds): Clinical Clennan BL (eds): Clinical Urography. Philadelphia: WB Saunders, 2000, pp 1245Urography. Philadelphia: WB Saunders, 2000, pp 1245--1250.1250.Hartman DS, Hartman DS, ChoykeChoyke PL, Hartman MS. From the RSNA refresher courses: a practical apPL, Hartman MS. From the RSNA refresher courses: a practical approach proach to the cystic renal mass. to the cystic renal mass. RadiographicsRadiographics 2004 Oct;24 2004 Oct;24 SupplSuppl 1:S1011:S101--15. 15. Israel GM, Israel GM, HindmanHindman N, N, BosniakBosniak MA. Evaluation of cystic renal masses: comparison of CT and MR MA. Evaluation of cystic renal masses: comparison of CT and MR imaging by using the imaging by using the BosniakBosniak classification system. classification system. RadiologyRadiology 2004 May;231(2):3652004 May;231(2):365--71.71.Netter FH. Atlas of Human Anatomy, Second Edition. 2001, p 313Netter FH. Atlas of Human Anatomy, Second Edition. 2001, p 313..NovellineNovelline RA. SquireRA. Squire’’s Fundamentals of Radiology. Cambridge: Harvard University Press Fundamentals of Radiology. Cambridge: Harvard University Press, 2004, s, 2004, pp 341pp 341--347.347.Wilson TE, Doelle EA, Cohan RH, Wojno K, Korobkin M. Wilson TE, Doelle EA, Cohan RH, Wojno K, Korobkin M. Cystic renal masses: a reevaluation of Cystic renal masses: a reevaluation of the usefulness of the the usefulness of the BosniakBosniak classification system. classification system. AcadAcad RadiolRadiol 1996 Jul;3(7):5641996 Jul;3(7):564--70.70.Wolf JS Jr. Evaluation and management of solid and cystic renal Wolf JS Jr. Evaluation and management of solid and cystic renal masses. masses. J J UrolUrol 1998 1998 Apr;159(4):1120Apr;159(4):1120--33.33.


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AcknowledgementsAcknowledgementsJason Jason HandwerkerHandwerker, MD, MDGillian Lieberman, MDGillian Lieberman, MDPamela Pamela LepkowskiLepkowskiLarry Larry BarbarasBarbaras, our webmaster, our webmaster

radiologic evaluation of renal cysts

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