Differential diagnosis of asymmetrical renal cortex thickening and solid renal tumours

Nowadays the number of asymptomatic, incidental tumors being detected increased as a result of the widespread use of noninvasive abdominal imaging modalities, including ultrasound and computed tomography (CT) and magnetic resonance imaging. The aim of the study is to analyze the atypical, complex morphologic changes and anatomical variants of renal structure, with tumor-like appearance. This is important especially in screening revealing tumors in asymptomatic patients or in patients with atypical symptoms. Material comprises a group of 186 patients in which the US examination was performed between 1996 and 2002, in 2nd Department of Radiology, Medical University of Lublin. In 20 patients the local thickening of renal cortex was found, protruding from the surface of the kidney, so-called "renal gibbus", constituting the anatomical variation. In eight cases the cortex thickening suggesting the presence of the renal gibbus, proved to be renal tumors. Diagnosing of small asymptomatic tumors, less than 3 cm in diameter, was difficult. They have appearance of protruding cortex thickening distorting the renal outlines. The assessment of renal outlines was an important morphologic factor. Small renal tumors showed anatomical anomalies. Regular tumor shape was rarely seen in larger tumors. The normal renal shape was more often seen in small tumors, while the large mass produces irregular distortion of renal outline. In four cases the oblique section of the renal pyramid has within the central part of kidney the appearance of oval pseudo-tumor. The differentiating of oval cortex thickenings protruding from the lateral renal margin--presenting "renal gibbuses"--and small renal tumors is difficult and requires supplementary helical CT examination with spatial reconstructions. Dynamic CT with early bolus of contrast agent and late sections is indicated. The lesion sizes, regularity of its margins, distortion of renal shape, echogenicity similar with the normal renal cortex were important in US examination. MR enhanced with DTPA and CT guided biopsy enables definite diagnosis.