[A rare anomaly presented with symptoms of acute abdomen: a third kidney located at right iliac fossa].

Supernumerary kidney is an extremely rare congenital anomaly of the urinary tract. A 39 year-old woman was admitted to the emergency unit with right lower quadrant pain. Physical examination revealed abdominal tenderness and defense on palpation of the right pelvic region. Blood and urine analysis revealed leukocytosis and urinary tract infection. Ultrasound examination demonstrated a suspicious mass which was thought to be a pseudokidney in the pelvis. Native kidneys were found in the normal anatomic position. Further investigation with computed tomography demonstrated a functioning third kidney which has located at the right iliac fossa in addition to normal excreting right and left kidneys. Acute abdomen like symptoms were secondary to the urinary infection of the third kidney and the urinary infection was successfully treated by antimicrobial and anti-inflammatory medication. We conclude that the infection of pelvic supernumerary kidney may create clinical symptoms of acute abdomen. Although extremely rare, congenital anomalies like supernumerary pelvic kidney should be included in the differential diagnosis.