RADIOLOGIC ASSESSMENT OF RENAL MASSES - IMPLICATIONS FOR PATIENT-CARE

THE ability to detect and characterize a mass arising in a kidney has been refined to an unprecedented degree over the past 2 decades due to technologic developments in sonography, computed tomography (CT), and magnetic resonance (MR) imaging (1-9). As these technologies have evo lved, the varied imaging characteristics of renal masses have become a pparent on the basis of both extensive formal investigations as well a s a widely shared clinical experience. Criteria for the radiologic dia gnosis of simple and complicated nephrogenic cysts (10-12), abscess (1 3,14), angiomyolipoma (15-17), hemangioma (18-21), benign and malignan t neoplasms (22-39), and inflammatory mass (40) have been thoroughly d escribed. The value of these advances can hardly be disputed. However, it is also clear that their prospective application in a given patien t is often subject to uncertainty or associated with wastefulness and futility (1,2,4). For example, the radiologic characteristics of diffe rent pathologic entities may overlap. Some features are highly diagnos tic of a certain pathologic condition, whereas others are equivocal (1 1,35,36,41-44). The use of multiple imaging modalities frequently prod uces data that are either redundant or contradictory. Further, radiolo gic interpretation is sometimes confounded by small size of the lesion (44,45). In any of these circumstances, the diagnostic radiologic eff ort may fail to provide data that usefully inform subsequent therapeut ic choices and/or patient outcome. Contemporary imaging has also opene d a Pandora's box, revealing conditions previously undetectable with i maging. These conditions include the discovery of a small solid mass o r a hyperattenuating fluid-filled mass in the kidney of an asymptomati c patient (25,46-64). Many of these small solid masses prove to be can cer at an early stage, and their early detection may account for the m uch heralded improvement in survival rates for renal cancer recently r eported (65-67). The true implications of these apparent salutary effe cts of CT and sonography, however, are yet to be determined, as emphas ized by questions regarding lead time bias of early detection and the biologic activity of incidentally discovered small lesions (68). In th is review of the role of the radiologic evaluation of a renal mass in clinical decision making, we use pathologic characteristics as our ben chmark. Radiologic data are considered as indirect analogues for these pathologic features. Further, a final tissue diagnosis is considered the province of the pathologist, not the radiologist. In this sense, a proper radiologic diagnosis is viewed as a prediction of a final tiss ue diagnosis, with an implied level of probability that is based on wh at is known about the inherent pathologic characteristics of the propo sed diagnosis, on the sensitivity of the modality or modalities used, and, to a lesser extent, on the prevalence and demographic features of the diagnoses under consideration.