[Bilateral urolithiasis with zonisamide developed for a short period of time in a 10-year-old girl with intractable epilepsy].

Zonisamide is an antiepileptic drug mainly used in patients with refractory epilepsy. One of the urological adverse effects caused by zonisamide is urinary lithiasis. We reported bilateral urinary lithiasis with zonisamide developed for a short period of time. A 10 year-old girl had been treated with zonisamide for intractable epilepsy for nine years. She progressively developed microscopic hematuria as well as crystalluria while being hospitalized for ventriculoperitoneal shunt infection. A computed tomography (CT) showed bilaterally hydronephrotic kidneys obstructed by multiple ureteral calculi. What was impressive was the fact that any single urinary calculus was not identified in a CT image taken just three weeks prior to this event. Then the diagnosis was made of zonisamide-induced bilateral urinary calculi and zonisamide treatment was discontinued. However, since the deterioration of renal function and left-sided hydronephrosis progressed, we performed the construction of right-sided percutaneous nephrostomy (PNS) and the transurethral placement of a left ureteral stent. Subsequently her condition was stabilized and all of these stones were discharged. The analysis of these stones showed mainly calcium phosphatic calculus. We eventually removed both the right PNS and the left ureteral stent. Since then, there has not been any recurrence thus far. We need to recognize the risk of progressively developing renal calculi during zonisamide treatment for a relatively short period of time in the face of dehydration.