[Excessive left retroperitoneal abscess of an unknown aetiology perforating into the peritoneal cavity: a case report].

Retroperitoneal abscesses present a relatively uncommon complication of diseases of various abdominal organs, although most commonly they are related to acute appendicitis of retrocoecal location. The paper presents the case of a healthy patient in whom an excessive left retroperitoneal abscess developed, perforated into the peritoneal cavity, and almost perforated through the skin in XIIth intercostal space. The patient had no abdominal symptoms or signs, but complained from slight pain in the left lumbar area. The diagnosis was established based on abdominal computed tomography scanning and an operative treatment by laparotomy. The evacuation and drainage of the abscess was effective and the patient recovered. Bacteriological examination of the pus from the abdominal cavity revealed single colonies of anaerobic Fusobacterium species. The cause of the occurrence of the abscess remained unknown.