Subacute reaction to endoscopic mucosal resection mimicking perforation.

A 25-year-old woman underwent routine day-case endoscopic mucosal resection (EMR) of two ascending colonic polyps. Six hours later she re-presented with severe abdominal pain. On examination she was tachycardic with tenderness and peritonism in the right lower quadrant. Urgent abdominal computed tomography (CT) did not reveal any signs of free intra-abdominal gas or fluid but did detect transmural thickening and oedema in the ascending colon and caecum. As there was no radiological evidence of perforation, the patient was managed conservatively and made a full recovery. The exact aetiology of this patient's symptoms is not known. She may have developed post-polypectomy electrocoagulation (a transmural diathermy injury), localised ischaemia of the colonic wall (secondary to the adrenaline used during EMR) or an allergic reaction to the dye used during EMR. As EMR is an increasingly used treatment modality in the management of colonic polyps, clinicians should have an awareness of the complications of treatment. We would advocate a low threshold for prompt CT investigation in any patient presenting with abdominal pain after EMR to detect any evidence of free intraperitoneal air. Patients without signs of perforation may be managed conservatively, as in this case.