Abstract
In the era of modern imaging, modalities like ultrasonography, computed tomography and magnetic resonance imaging diagnosis of renal mass lesions has become more accurate. Nevertheless, rare cases of renal adenocarcinoma and other primary renal tumors have been rarely reported to mimic pyonephrosis, renal abscess, perinephric abscess or tuberculosis. We report, for the first time in literature, a case of Wilms' tumor mimicking as a case of pyonephrosis. The incidence, possible causes and implications of such a misdiagnosis and the measures to avoid the same are discussed.