Objective: To report a case of ventriculoperitoneal (VP) shunt malfunction caused by an abdominal pseudocyst, a rare complication of VP shunting.
Case: A three-year-old girl presented to the emergency unit with severe headache. She also had constipation, with no passage of stools for the past five days. Vomiting, fever, seizures, or vision changes were absent. She had been diagnosed with hydrocephalus at the age of three months with subsequent VP shunt placement. A firm, non-tender, non-erythematous bulging of the shunt was palpable on the right frontotemporal region. No other neurological deficits were found. On the abdomen, a fecal mass was palpable on the right and left periumbilical regions, and a fluctuant, non-tender mass with a diameter of 3-4 cm was palpable on the right upper quadrant. Serial plain abdominal radiography revealed prominent fecal mass which persisted but diminished after defecation was encouraged using rectal bisacodyl, oral lactulose, and probiotics. However, the headache persisted despite repeated passage of stools. An abdominal ultrasound was performed and showed a 1.03x1.45x4.72 cm pseudocyst circumscribing the distal shunt catheter tip. The patient underwent immediate shunt repair and pseudocyst drainage, after which the headache resolved. She was discharged in stable condition three days post-operatively.
Conclusion:  An abdominal pseudocyst should be considered in patients with signs of VP shunt malfunction accompanied by gastrointestinal complaints. Abdominal ultrasound should be promptly obtained in such patients when stool evacuation fails to produce relief of the signs and symptoms of shunt malfunction.