False positive peritoneal lavage due to retroperitoneal haematoma

Many papers have described the excellent dependability of peritoneal lavage in detecting intraperitoneal blood. In our series this investigation has resulted in unnecessary laparotomies in 6 patients out of 33 (18 per cent). Massive retroperitoneal haematomas, mostly due to pelvic fractures, were the cause of these false positive results. Careful interpretation of positive peritoneal lavages in the presence of significant pelvic fractures is indicated.