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From the question on page 33

The CT scan in fig 1 of the question shows a thickened caecum with adjacent fat streaking, but no evidence of abdominal free air or a collection. The specimen of the right colon shows perforation within a central punched out area at the lower pole of the caecum at the site of submucosal injection site (stains of methylene blue still seen) (fig 1).

Figure 1 The right hemicolectomy specimen.

Laparotomy revealed a 1.5×1.5 cm perforation in the lower pole of the caecum adjacent to the appendix, sealed with small bowel mesentery, and 30 ml of purulent fluid within the pelvis, with all other factors normal. Histological analysis of the specimen confirmed marked oedema, ulceration of the colonic mucosa and a perforation with evidence of localised peritonitis. There was a transmural reaction at the site of the perforation involving the mucosal and serosal surfaces, with the presence of fibrinoid necrosis and chronic inflammatory cells. A small remnant of a sessile polyp of just 2 mm was seen next to the ulcerated area which was adenomatous in nature with low grade dysplasia, and a fibrinopurulent exudate with numerous bacterial cocci was present within the colonic wall.

The delayed presentation in conjunction with the laparotomy and histological findings is consistent with a localised caecal perforation as a complication of the submucosal injection. This could be a consequence of a serosal tear caused by a misplaced EMR solution injection into the muscle or serosal layers, or localised ischaemia caused by the submucosal injection. Interestingly, a study1 has reported histological ischaemic features such as ulceration/necrosis and fibrinoid necrosis of vessel walls in the resected specimens when methyl blue was used as a colonic tattooing agent, but of course another offending agent could well be the low dose of adrenalin used within the mixture. An alternative explanation for the ischaemia is that a misplaced submucosal injection caused tamponade of the anterior or posterior caecal arteries, although one might expect a more profound ischaemia with an earlier presentation in this scenario. To our knowledge, such a complication of just a submucosal injection has not been described, even in large series of colonic EMRs.2

Colonoscopists should be aware that serious complications can occur from the submucosal injection during a right-sided colonic EMR.

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