Radiologic Evaluation of Renal Cysts

Eugene K. Cha, HMS III November 2004 Radiologic Evaluation of Renal Cysts Eugene K. Cha, Harvard Medical School III

Renal Anatomy Netter FH. Atlas of Human Anatomy, Second Edition. 2001, p 313. 2

HPI: 50 yo M p/w: Patient #1: MM 7 d of flank/back pain 2 d of atypical chest pain MM r/o for MI, r/o aortic dissection HD #3: MM developed acute L-sided L flank pain Initial Flank Pain Radiologic Workup: supine and upright plain films of abdomen 3

Patient MM: KUB Paucity of bowel gas on left; suggestion of soft-tissue mass PACS, BIDMC 4

Menu of Imaging Tests for Renal Masses Excretory Urography / Intravenous Pyelogram (IVP) Limited sensitivity for small renal masses 67% for RCC 3 cm or less US Reliable identification of simple renal cysts (most renal masses) Inexpensive CT Current gold standard for evaluation of renal masses MR For patients with contrast allergy Elevated serum creatinine level Hyperdense renal 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. 5

Patient MM: Further Radiologic Workup Next, Patient MM had a non-contrast CT evaluation of his abdomen Non-contrast (non-ideal) because of patient s compromised renal function 6

Patient MM: Non-contrast CT Abdomen #1 (Axial Images) well-circumscribed, low-attenuation lesion = liver cyst PACS, BIDMC well-circumscribed, high-attenuation lesion in kidney low-attenuation lesions in kidneys 7

Patient MM: Non-contrast CT Abdomen #2 (Axial Image and Sagittal Reconstruction) cyst in kidney, calcification PACS, BIDMC perinephric hematoma w/ adjacent stranding 8

Patient MM: Non-contrast CT Abdomen #3 (Coronal Reconstructions) liver cysts PACS, BIDMC perinephric hematoma w/ adjacent stranding 9

Patient MM: Renal US #1 (Transverse R) cyst PACS, BIDMC 10

Patient MM: Renal US #2 (Sagittal( R) Enlarged right kidney PACS, BIDMC 11

PMH: Patient MM Adult polycystic kidney disease Chronic renal failure HTN Hyperlipidemia Atrial fibrillation Diagnosis: Complication of PCKD w/ acute left kidney subcapsular hemorrhage into perinephric space 12

Bosniak Classification: Cystic Renal Masses Category I: simple benign cysts Category II: minimally complicated cysts Category IIF: minimally complicated cysts that require radiologic follow-up Follow-up in 3 months, then 6 months, then 1 year Category III: moderately complicated cysts Exhibit some radiologic features seen in malignancy Need surgical exploration Category IV: clearly malignant cystic carcinomas Bosniak 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. 13

Features of Bosniak Category I Bosniak Category I = simple benign cysts US Sharply marginated,, smooth walls Anechoic Good through transmission CT Sharp margination and demarcation from surrounding renal parenchyma Smooth, thin wall Water density content, homogeneous throughout (0-20 HU) No enhancement following IV contrast Bosniak MA. The current radiological approach to renal cysts. Radiology 1986 Jan;158(1):1-10. 14

Review of Patient MM: Renal US #1 Cyst demonstrates: Sharply marginated,, thin walls Anechoic Good through transmission Category I PACS, BIDMC 15

Complications of Simple Cysts Simple Cysts complicated by: Hemorrhage Infection Inflammation Ischemia Host response: Inflammatory cells Granulation tissue Neovascularity Complicated Cysts: Calcification Hemorrhage Septations Wall Thickening Nodularity at Gross Inspection 16

CT Criteria for Bosniak Classification Criteria Cat I Cat II Cat IIF Cat III Cat IV Wall Septations Calcifications Density pre-contrast Enhancement Thin None None Thin Few, thin Few, thin 0-20 HU 0-20 HU 0-20 HU No No (except hyperdense cyst) No More than thin More than few, thin More than few, thin Thick or nodular Numerous, thick Coarse 0-20 HU > 20 HU No Yes Bosniak 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. Wolf JS Jr. Evaluation and management of solid and cystic renal masses. J Urol 1998 Apr;159(4):1120-33. 17

Review of Patient MM: CT #2 Cyst characteristics: Thin wall Few, thin septations Few, thin calcifications Density: 15 HU Category II PACS, BIDMC 18

Patient #2: JD, Bosniak Category III US: Complicated cystic lesion with some solid-appearing elements among cystic spaces CT: Multiple septations Wall: moderate thickness Minimal enhancement Category III Nephrectomy: : RCC Bosniak MA. The current radiological approach to renal cysts. Radiology 1986 Jan;158(1):1-10. 19

Differential Dx of Renal Masses and Cysts Simple Cyst (Bosniak( Cat. 1) Other Probable Benign Cysts Infected cyst, minimally complicated cyst, hyperdense cyst (Bosniak Cat. 2), polycystic kidney disease Cystic Masses Possibly Assoc. w/ Malignancy von-hippel Hippel-Lindau,, tuberous sclerosis, acquired cystic disease, multilocular cystic nephroma,, (Bosniak( Cat. 3 and 4) Definable Benign Solid Masses Angiomyolipoma,, hematoma, renal anomaly, infarction, lobar nephronia, xanthogranulomatous pyelonephritis Probable Malignant Solid Masses RCC, transitional cell carcinoma, metastases, lymphoma, oncocytoma,, 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. 20

Bosniak Classification System Identifies: Lesions that do not require further work-up Category I Category II Lesions requiring radiologic follow-up Category IIF Lesions requiring invasive / surgical work-up Category III Category IV 21

Utility of Bosniak Classification System Aronson et al. (1991) Retrospective review of CT/US findings in 16 pathologically proven renal cystic masses Cat. II lesions: All benign (4/4) Cat. III lesions: 3/7 benign, 4/7 malignant 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. 22

Utility of Bosniak Classification System Wilson et al. (1996) Retrospective review of CT scans for 20 pts, 24 cystic renal masses biopsied or surgically removed Cat. I: All benign (7/7) Cat. II: 1/5 benign, 4/5 malignant Cat. III: All malignant (4/4) 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. 23

Utility of Bosniak Classification System Curry et al. (2000) Two-center, prospective and retrospective analysis of properly performed renal CT scans of 109 pts, 116 renal cystic lesions Cat. I and Cat. II: All benign (15/15) Cat. III: 29/49 malignant Cat. IV: All malignant (18/18) Prospectively 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. 24

Bosniak Classification System: Summary Study Cat. I Cat. II Malignant Lesions Cat. III Cat. IV Total Aronson et al. 0/0 0/4 5/9 7/7 20 Brown et al. 0/2 0/4 3/12 4/6 24 Wilson et al. 0/7 4/5 4/4 6/6 22 Cloix et al. 1/2 1/7 4/13 8/10 32 Siegel et al. 0/22 1/8 5/11 26/29 70 Curry et al. 0/4 0/11 29/49 18/18 82 Total 1/37 (2.7%) 6/39 (15.4%) 50/98 (51.0%) 69/76 (90.8%) 250 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. 25

Conclusions Renal cysts are commonly found on routine imaging By evaluating morphology, wall thickness, calcification, cyst attenuation, septations,, and enhancement, it is possible to identify: Lesions that are benign Lesions that should be managed with radiologic follow-up Lesions that require biopsy or surgical excision 26

References Amendola MA et al. Small renal cell carcinomas: resolving a diagnostic dilemma. d Radiology 1988; 166:637. Aronson S et al. Cystic renal masses: usefulness of the Bosniak classification. Urol Radiol 1991; 13(2):83-90. Bosniak MA. The current radiological approach to renal cysts. Radiology 1986 Jan;158(1):1-10. 10. Bosniak MA. Difficulties in classifying cystic lesions of the kidney. Urol Radiol 1991;13(2):91-3. 3. Bosniak MA. Problems in the radiologic diagnosis of renal parenchymal tumors. Urol Clin North Am 1993; 20:217-230. 230. 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. Harisinghani MG, Maher MM, Gervais DA, McGovern F, Hahn P, Jhaveri K, Varghese J, Mueller PR. Incidence of malignancy in complex cystic renal masses (Bosniak( category III): should imaging-guided guided biopsy precede surgery? AJR Am J Roentgenol 2003 Mar;180(3):755-8. 8. Hartman DS. Overview of renal cystic disease: IN: Pollack HM, McClennan BL (eds): Clinical Urography. Philadelphia: WB Saunders, 2000, pp 1245-1250. 1250. Hartman DS, Choyke PL, Hartman MS. From the RSNA refresher courses: a practical approach proach to the cystic renal mass. Radiographics 2004 Oct;24 Suppl 1:S101-15. 15. 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. Netter FH. Atlas of Human Anatomy, Second Edition. 2001, p 313. Novelline RA. Squire s s Fundamentals of Radiology. Cambridge: Harvard University Press, s, 2004, pp 341-347. 347. 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. 70. Wolf JS Jr. Evaluation and management of solid and cystic renal masses. J Urol 1998 Apr;159(4):1120-33. 27

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