[Sonographical diagnosis of pneumoretroperitoneum as a result of retroperitoneal perforation]

A retroperitoneal perforation is a rare incident. It can occur as a complication of ERCP with papillotomy (0.2-0.5%). Leakage of contrast agent during endoscopy raises the suspicion that this complication has occurred but doesn't always give sufficient information about the leakage extent. In the case of extreme gas emission, a plain abdominal X-ray shows classic pneumoretroperitoneum. The abdominal CT scan can display small amounts of free air which is why it is used for diagnosis in such cases. Ultrasonography also provides a reliable diagnosis and is a good method for monitoring the progression of the condition. Alternative causes of pneumoretroperitoneum can be: trauma, inflammation, infection, tumor as well as ERCP and other interventional procedures, especially endoscopies. Presacral retroperitoneal pneumoradiography was used for the diagnosis of retroperitoneal tumors in the 70 s but is no longer used today. Perforations into the retroperitoneal space come from several locations in the gastrointestinal tract. In the different types of lesions the gas can penetrate the compartments and reach as far as the mediastinum, the intraabdominal cavity, subcutaneum (cervical) or the scrotal compartment (compartment shift). Based on 11 cases (7 perforations during ERCP, 2 perforation during colonoscopy, 2 cases with damage of the distal esophagus), we show the most extensive presentation of the sonographical picture of pneumoretroperitoneum. Typical signs on abdominal ultrasound are an increased echogenicity around the right kidney ("overcasted" or "covered" kidney), air dorsal to the gallbladder, around the duodenum and the head of the pancreas and especially ventral to the great abdominal vessel which can lead to the picture of "vanishing" vessels. The extent of free air is easy to assess. Even very small amounts are detectable ventral to the right kidney. In most cases, a conservative approach with no oral intake, antibiotic coverage, and analgesia in close gastroenterological-surgical cooperation is indicated. Especially after ERCP abscess formation is repeatedly described, sometimes even with a lethal outcome. Sonography is a suitable method for detecting free air in the retro-peritoneum. Pneumoretroperitoneum following bowel-perforation can be effectively shown by ultrasound, it is possible to assess the extent of free air, and sonographic monitoring of the treatment is possible and successful.