http://radiographics.rsna.org/content/24/suppl_1/S101.full
David S. Hartman, MD ; Peter L. Choyke, MD ; Matthew S. Hartman, MD

1 From the Department of Radiology, Milton S. Hershey Medical Center, Penn State University School of Medicine, HO66, 500 University Dr, Hershey, PA 17033 (D.S.H.); the Department of Radiology, Clinical Center, National Institutes of Health, Bethesda, Md (P.L.C.); and the Department of Radiology, Emory University School of Medicine, Atlanta, Ga (M.S.H.). Presented as a refresher course at the 2003 RSNA scientific assembly. Received March 29, 2004; revision requested April 28 and received May 14; accepted May 25. All authors have no financial relationships to disclose.

The pathologic and imaging features of the renal cyst have been well described. A fluid-filled lesion is considered a cystic mass (ie, not a simple cyst) when it has any of the following features: calcification, high attenuation (>20 HU) at computed tomography, signal intensity not typical of water at magnetic resonance imaging, septations, multiple locules, enhancement, wall thickening, or nodularity. There are two important causes of a cystic renal mass: a complicated simple cyst (eg, one with hemorrhage, infection, or ischemia) and cystic renal cell carcinoma. At radiologic evaluation of such masses, it is imperative that optimal imaging techniques be used. Masses with calcification, high attenuation or high signal intensity, or septations can be categorized as benign (no further evaluation required), as requiring follow-up (probably benign), or as requiring surgery. Lesions requiring surgery can be benign or malignant at microscopic examination. Lesions that are multiloculated or demonstrate enhancement, wall thickening, or nodularity usually require surgery. When multiple features are present (eg, calcification and enhancement), the mass should be managed according to its most aggressive feature. Likewise, when there are conflicting findings at evaluation with different imaging modalities, the mass should be managed according to the most aggressive finding.