Peritonitis is a rare complication of ventriculoperitoneal shunt. Shunt infection may be the cause in patients with ventriculoperitoneal shunt, who have acute abdomen. Specific clues taken from patient's history, physical examination and some further investigations may clarify the diagnosis. This case is a 25-years-old male with a ventriculoperitoneal shunt who presented symptoms of acute abdomen. The patient was admitted with complaints of abdominal pain. There were no neurologic signs or symptoms. Physical examination on admission revealed a mass in the right lower abdomen and abdominal muscular guarding with rebound tenderness. Laboratory studies showed leukocytosis of the peripheral blood. Abdominal ultrasound demonstrated a mass and the preoperative diagnosis was appendicitis. On abdominal exploration, appendix was found to be normal but a catheter infection related omental necrosis was present. Surgical therapy was carried out by withdrawal of the catheter and segmental resection of the omentum. The patient was discharged on seventh day postoperatively.