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Is It Safe to Just Follow Moderately Complex Cystic Kidney Lesions?

In a retrospective analysis, researchers showed that few Bosniak category IIF lesions were malignant.

Cystic lesions of the kidney are encountered frequently as incidental findings on abdominal imaging. Nonenhancing cysts with hairline-thin walls and no septa (or a few hairline-thin septa) are virtually always benign and require no further intervention. However, some cystic lesions have features that are more complex (e.g., many thin septa, minimal thickening of a septum or wall, or nodular calcification) without having clearly malignant characteristics. In this retrospective study, radiologists describe outcomes for 42 of these moderately complex cystic kidney lesions in 41 patients.

Patients were followed with periodic computed tomography. During a mean follow-up of 5.8 years, 2 patients were diagnosed with cystic renal cell carcinoma. In one case, the lesion had enlarged and had developed characteristics that were more complex at 3 years. In the other case, the lesion had not enlarged, but it had become more complex at 1.3 years.

Comment: Because only 2 of 42 lesions in this series eventually were found to be malignant, and because cystic renal neoplasms have better prognoses than do solid ones, the authors conclude that "a surgical approach does not seem justified" for most patients with moderately complex cystic renal lesions. The authors acknowledge limitations of their analysis, including its retrospective nature and lack of pathologic proof of benignity in all cases. Perhaps the most important message for primary care physicians is that experienced radiologists should interpret imaging studies in which moderately complex cystic renal lesions are seen.

— Allan S. Brett, MD

Published in Journal Watch General Medicine October 10, 2003

Citation(s):

Israel GM and Bosniak MA. Follow-up CT of moderately complex cystic lesions of the kidney (Bosniak category IIF). AJR Am J Roentgenol 2003 Sep; 181:627-33.

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