Urinary tract infection due to Staphylococcus saprophyticus: a clinical presentation mimicking a renal stone in a male adolescent.

In the context of increasing flank pain, hematuria, lack of toxicity, and absence of a stone on imaging studies, the cause may be a urinary tract infection due to Staphylococcus saprophyticus. When symptoms suggest renal lithiasis but intravenous pyelogram, renal ultrasonography, or renal cortical scan is negative for obstructive uropathy and dimercaptosuccinic acid scanning suggests acute pyelonephritis, initial antibiotic selection should include coverage for this organism, pending urine culture and sensitivity results.