Renal Pseudotumors: An Anatomic-Radiologic Classification

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Abstract
A classification of pseudotumors is offered based on current understanding of renal anatomy and pathology. Rather than restrict the range of renal pseudotumors to parenchymal processes simulating renal mass lesions it is proposed to enlarge the concept to include all normal structures that are part of the kidney or related to it but to exclude all pathologic lesions. The proposed new definition of renal pseudotumor is a real or simulated renal mass urographically resembling neoplasm but histologically composed of normal tissue. Pathologic lesions, such as localized hydronephrosis, abscess and hematoma, are believed to represent a too diverse and heterogeneous group to merit inclusion within this classification. The importance of recognizing the curious pseudotumor is, of course, to achieve a correct diagnosis of a benign innocuous entity and, thereby, obviate an unnecessary operation. Once diagnosed the pseudotumor requires no treatment and further investigations into its nature are clinically unnecessary. Renal pseudotumors usually are first detected at excretory urography (IVP) but cannot always be differentiated from pathologic entities by an IVP alone. However, it has been shown that in the case of parenchymal pseudotumors this distinction can be made simply and accurately in almost all instances by radionuclide renal imaging.