RESUMEN
An endoscopic mucosal resection (EMR) is an effective and safe therapeutic technique for treating a patient with a laterally-spreading tumor (LST). Colonoscopic-procedure-related complications are noted to be about 2.8% worldwide, and a perforation is the most common. Most colon perforations cause pneumoperitoneum. However, a perforation within the retroperitoneal portion of the colon (rectum and some of sigmoid colon) may cause an extraperitoneal perforation, and the leaking free air may induce pneumoretroperitoneum, pneumomediastinum, and subcutaneous emphysema, depending on the amount of discharged air. Herein, we present the case of a patient with an extraperitoneal colon microperforation which manifested as pneumoretroperitoneum, pneumomediastinum, and subcutaneous emphysema after an EMR for a sigmoid LST, which was successfully treated with medical treatment and endoscopic clipping.