BACKGROUND: Peritoneal catheters may be used routinely in children undergoing cardiac surgery. Removal of the catheter is often complicated by omental herniation, which can cause intraperitoneal bleeding, peritonitis, and bowel obstruction. Instillation of saline into the catheter before removal is used in some institutions as a preventive measure, but the practice has never been investigated. OBJECTIVE: To determine the effectiveness of instilling saline into peritoneal catheters before their removal in reducing the occurrence of omental herniation and to determine risk factors for omental herniation. METHODS: A total of 404 patients with peritoneal catheters in place were randomized to either the control or the study group. The study group (n = 204) had saline (1 mL/kg; maximum, 10 mL) instilled into the catheter before the catheter was removed; the control group (n = 200) did not. Extrusion or no extrusion of omentum was recorded. Other data collected included the child's weight, the length of time the catheter was in place, whether peritoneal dialysis was performed, and whether the child was pharmacologically paralyzed when the catheter was removed. RESULTS: Extrusion of omentum occurred in 39% of the study group and in 33% of the controls. Results of logistic regression analysis suggested that omental herniation was more common in smaller children, children whose catheters remained in place longer, and children who were not pharmacologically paralyzed when the catheter was removed. CONCLUSIONS: Instillation of saline does not appear to reduce the occurrence of omental herniation. Further research into strategies to reduce this complication is recommended.