Xanthogranulomatous pyelonephritis masquerading as occult malignancy.

Xanthogranulomatous pyelonephritis (XGP) can present with weight loss, anemia, leukemoid reaction, and generalized debility; there may be no signs or symptoms referable to the urinary tract. Confusion between XGP and renal adenocarcinoma is well recognized, but other malignancies can also be simulated. Case histories of patients with proved XGP whose clinical presentations suggested occult malignancies are recorded. Proteus urinary tract infection, calculi, and a nonvisualizing kidney on intravenous pyelogram should suggest the correct diagnosis. The pathology, bacteriology, diagnosis, and treatment are reviewed.