An enormous abdominal mass associated with acute renal failure.

We report a 67-year-old man with acute uric acid nephropathy, secondary to spontaneous tumor lysis syndrome, that presented itself as a huge intra-abdominal tumor that led to acute renal failure, hyperuricemia, and azotemia. Initial finding of hydronephrosis detected by ultrasonography led us to believe that the azotemia and decreasing amount of urine resulted from obstructive uropathy, a common complication of malignancy, caused by either a direct renal invasion or a urinary outflow tract compression because of a tumor mass effect. However, clinical observations and the response to therapeutic intervention confirmed the diagnosis of spontaneous tumor lysis syndrome, which is a rare cause of acute uric acid nephropathy.