A Rare but Life-Threatening Complication of Direct Endoscopic Necrosectomy: Tension Pneumoperitoneum With Pneumothorax and Hypercapnia due to Walled-Off Necrosis Rupture.

Endoscopic ultrasonography (EUS)-guided drainage followed by direct endoscopic necrosectomy (DEN) is widely used as a minimally invasive treatment for walled-off necrosis (WON). While this approach is considered effective and safe, serious complications may occur. We report a case of carbon dioxide (CO2)-related tension pneumoperitoneum accompanied by severe hypercapnia during DEN. A 65-year-old man with gallstone pancreatitis developed a large WON causing gastric outlet obstruction. He underwent EUS-guided transgastric drainage with placement of a lumen-apposing metal stent (LAMS), followed by planned DEN sessions under CO2 insufflation with propofol sedation. During the second DEN session, the LAMS became dislodged, and subsequent DEN was continued after balloon dilation of the endosonographically created route. During the fourth DEN session, the patient experienced sudden oxygen desaturation. Imaging revealed extensive free air in the abdominal and thoracic cavities, and arterial blood gas analysis showed severe hypercapnia. Emergency exploratory laparotomy revealed disruption of the WON wall with communication into the abdominal cavity. Surgical necrosectomy and abdominal irrigation were performed. The patient recovered uneventfully. This case highlights a rare but potentially serious CO2-related complication of DEN and underscores the need for meticulous control of intracavitary pressure and close respiratory monitoring during the procedure.