Massive pneumoperitoneum with abdominal pain and fever mimicking delayed perforation following endoscopic resection: A case report

Pneumoperitoneum has been reported as an intraprocedural or acute postprocedural adverse event resulting from advanced endoscopic intervention. Here, we report a case of a massive pneumoperitoneum-mimicking delayed perforation after colonic endoscopic submucosal dissection. A 60-year-old man received endoscopic submucosal dissection for a large colon polyp. Room air was inadvertently used in the first half of the procedure. After 12 hours, the patient developed fever, abdominal pain, and bilateral shoulder pain, and massive pneumoperitoneum was detected through plain film and computed tomography. After urgent diagnostic paracentesis, the patient's symptoms dramatically improved, and laparotomy was avoided. Massive pneumoperitoneum rarely occurs in patients receiving complex and long-standing endoscopic procedures, and it may manifest similarly to delayed perforation. Prompt diagnostic paracentesis is valuable when the diagnosis is uncertain.