Subcutaneous migration of distal ventriculoperitoneal shunt catheter caused by abdominal fat pad shift--three case reports.

Aberrant migration of a ventriculoperitoneal shunt catheter is an infrequent complication and the mechanism is unclear. We report three cases of subcutaneous migration of the distal catheter. The relationship between thick abdominal fat and catheter migration was suggested in all three cases. Abdominal radiography showed that the subcutaneous fat pad had slid down in the standing position, pulling the catheter out of the peritoneal cavity. We suggest the following mechanisms: Changing from the supine position to the standing position caused subcutaneous fat pad to slide down, the shifted fat pad pulled out the catheter from the peritoneal cavity, and anchoring prevents the catheter returning into the peritoneal cavity. Subcutaneous fat pad shift might act as a "windlass," resulting in coiling of the catheter in the subcutaneous tissue. During daily life, the peritoneal catheter was pulled out repeatedly and finally was coiled within the subcutaneous fat tissue. Placement of the catheter between the subcutaneous fat pad and the abdominal muscle wall will help to avoid this rare complication. This preventive measure is especially recommended for obese patients with a high risk of subcutaneous migration of the peritoneal catheter.