Renal Staghorn Calculus?

A 61-year-old woman presented with a history of recent cystitis accompanied by dark urine and back pain. Two right-sided renal calculi had been spontaneously excreted decades earlier. An abdominal ultrasound examination was suggestive of a huge right-sided renal pelvic stone. On the basis of the intravenous urography images (Fig. 1), the diagnosis of a staghorn calculus was established, and percutaneous lithotomy was recommended. Before surgery, the uncommon shape of the calculus was considered suspicious. Abdominal computed tomography scan (Fig. 1, inset) and subsequent renovasography disclosed that a calcified aneurysm of the right renal artery caused the impressive imaging findings, thus creating a potentially dangerous clinical pitfall.