A case of gastrointestinal perforation following transarterial embolization for an intramural hematoma after cold snare polypectomy of an adenoma in the transverse colon.

We encountered a case of a large hematoma developing with perforation shortly after a cold snare polypectomy for a colorectal adenoma. The patient underwent cold snare polypectomy for a 3-mm type Is lesion in the transverse colon at another facility. Two hours later, she visited the emergency room due to abdominal pain. Contrast-enhanced computed tomography revealed a 70 mm, high-intensity mass in the transverse colon with contrast extravasation. We attempted transcatheter arterial embolization to stop the bleeding. Several hours later, the anemia had not worsened, but the severe abdominal pain persisted. Urgent laparoscopic right hemicolectomy was performed due to the possibility of gastrointestinal perforation. The surgery was successfully completed. Pathology reports confirmed the presence of an intramural hematoma in the proximal transverse colon with hemorrhagic infiltration of all layers, along with extensive ischemic changes. A perforation was identified in this area, with mucosal defects observed near the hole, possibly due to cold snare polypectomy.