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Mr Will Finch MBBS BSc(Hons) MRCS Urology SpR Edith Cavell Hospital. Atypical Renal Cysts. Bosniak Classification. When to…. Discharge, survey or operate. Bosniak Classification of Renal Cystic Disease. Category I.
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Mr Will Finch MBBS BSc(Hons) MRCS Urology SpR Edith Cavell Hospital Atypical Renal Cysts
Bosniak Classification • When to…. • Discharge, survey or operate
Bosniak Classification of Renal Cystic Disease • Category I. • simple benign cysts showing homogeneity, water content, and a sharp interface with adjacent renal parenchyma, with no wall thickening, calcification, or enhancement. • Category II. • cystic lesions with one or two thin (≤ 1 mm thick) septations or thin, fine calcification in their walls or septa (wall thickening > 1 mm advances the lesion into surgical category III) and hyperdense benign cysts with all the features of category I cysts except for homogeneously high attenuation. A benign category II lesion must be 3 cm or less in diameter, have one quarter of its wall extending outside the kidney so the wall can be assessed, and be nonenhancing after contrast material is administered. • Category IIF • minimally complicated cysts that need follow-up. This is a group not well defined by Bosniak but consists of lesions that do not neatly fall into category II. These lesions have some suspicious features that deserve follow-up up to detect any change in character. • Category III. • true indeterminate cystic masses that need surgical evaluation, although many prove to be benign. They may show uniform wall thickening, nodularity, thick or irregular peripheral calcification, or a multilocular nature with multiple enhancing septa. Hyperdense lesions that do not fulfill category II criteria are including in this group. • Category IV. • nonuniform or enhancing thick wall, enhancing or large nodules in the wall, or clearly solid components in the cystic lesion. Enhancement was considered present when lesion components increased by at least 10 H.
Bosniak II and IIF • Number of septae • Group 1 No septae • Group 2 1-4 septae • Group 3 5-9 septae • Group 4 >9 septae • Thickness of wall and/or septae • Group 1 Wall only • Group 2 Hairline thin • Group 2F Minimally thickened • Group 3 Grossly thickened (>1mm) and irregular Israel et al. Radiology 2004;231:365-71
Bosniak and Cancer Risk Warren et al. BJUI 2005;95:939-42
Value and Danger of Bosniak ClassificationLoock et al. Prog Urol 2006 (French) • 37 patients • Stage II 6 pts No cancers • Stage IIF 10 pts 2 cancers (20%) • Stage III 14 pts 4 cancer (30%) • Stage IV 7 pts 6 cancer (86%) • Stage I&II No Follow up required • Stage IIF Indeterminate risk requires FU • Stage III&IV Surgical management
Further Clarification? • 41 patients with Stage IIF • Nearly 6yrs FU • 36 masses remained unchanged on CT • 3 masses got smaller • These were considered benign • 2 lesions increased in size and were removed, both were RCC’s Israel G, Bosniak Ml. Am J Roentgenol 2003;181:627-3
Clarification hot off the press?? Does Stage IIF improve accuracy of Bosniak classification? O’Malley et al. J Urol 2009;182(3):1095 • 112 pts • Stage IIF 81 pts • Stage III 31 pts • Median FU of 15 months • 14.8% of Bosniak IIF lesions progressed in complexity (median of 11 months) • No differences in tumour or patient characteristics for cysts that progressed and those that remained stable • 33 patients with Stage III cysts had surgery • Malignancy rate 81.8% • Suggests increased accuracy of classification by low rate of progression (14.8%) for Bosniak IIF, and very high rate of malignancy in Stage III group (81.8%)
What should Follow up be? • Stage I No FU • Stage II No FU • Stage IIF Scan @ 6/12 and 1yr If no evidence of progression – discharge? Or Scan @ 6/12, 1yr and 2yrs and then discharge? • Stage III/IV Surgical exploration
Conclusions • No good quality studies to answer question of FU • Subjective assessment on USS, less so on CT • It appears that if Stage IIF diagnosed accurately • Low risk of progression ~ 15% - 20% • Progression occurs on average around 1yr • Would be sensible that accurate rpt imaging reflects this • Classification based on CT, but role for MRI or CEUS • Individual patients choice re balance of risk and FU or exploration?