Abstract The case of intra- and retroperitoneal irrigation solution after hip arthroscopy of a 15-year-old girl is presented. She underwent hip arthroscopy for intra-articular adhesiolysis after previous surgical dislocation of the hip for the treatment of femoroacetabular impingement. Arthroscopy was performed in the lateral decubitus position without traction to debride the peripheral joint compartment. The irrigation pressure was set at 40 mm Hg. There were no intraoperative complications. By the end of surgery, the anesthesiologist reported a drop in the patient's body temperature from 36.3° to 34.5°C. Postoperatively, she complained about abdominal swelling and discomfort. Abdominal sonography revealed approximately 2 to 3 L of intra- and retroperitoneal liquid, which was considered to be irrigation fluid. The irrigation fluid was absorbed within 16 hours without further treatment. The only possible way the irrigation fluid could have flown was a retroperitoneal course along the iliopsoas muscle and the iliac vessels with intraperitoneal perforation along their course. We observed at arthroscopies that irrigation pressure incidentally can rise to 140 mm Hg when leaking of fluid through the portals occurs. Intra-abdominal fluid is a potentially devastating complication. A sudden drop of body temperature has to raise suspicion for intra-abdominal leaking of irrigation fluid.