Radiographically occult ureteral calculi in an HIV-positive child undergoing indinavir therapy

Helical CT has been shown to be a sensitive and specific tool for the rapid diagnosis of obstructing urinary tract calculi. AIDS patients taking the protease inhibitor indinavir, however, can develop urinary tract calculi that are invisible on CT. We present a case of a 9-year-old HIV-positive girl who developed acute ureteral obstruction while taking indinavir. Helical CT after the administration of intravenous contrast demonstrated signs of ureteral obstruction although no obstructing calculus was visualized. This case demonstrates that obstructing ureteral calculi secondary to indinavir therapy may not be visualized with helical CT, unlike nearly all other obstructing calculi. When secondary signs of obstruction are seen in these patients, the radiologist must have a high index of suspicion for urinary tract calculi even without direct visualization of a stone.