Extra-abdominal lumbar abscesses caused by retroperitoneal gastrointestinal perforations through the lumbar triangle of Petit: report of two cases diagnosed by CT

Extra-abdominal abscesses of gastrointestinal origin developing within the lumbar subcutaneous tissues are extremely rare. We report two cases of retroperitoneal bowel perforation presenting spontaneously at admission with a lumbar abscess trespassing the lumbar triangle of Petit, a classical “locus of minus resistencia” of the posterior abdominal wall. The first case was caused by perforation of a retrocecal appendicitis—being concomitantly responsible of a necrotizing fasciitis of the thigh—and in the second case perforation was caused by left colonic diverticulitis. In both cases, the full diagnosis was made with abdominal CT. The patients were threatened by a two-step surgical approach comprising a direct posterior percutaneous drainage of the abscess followed by classical laparotomy.