A dramatic finding at colonoscopy: cause for concern?

Case report A 66-year-old woman with a background of diverticular disease, hypertension, chronic kidney disease and amaurosis fugax was referred to our unit for colonoscopy as part of the bowel cancer screening programme following a positive faecal occult blood result. Scope trauma, haemmorhagic colitis or, rarely colonic perforation may result in similar appearances. 1 An association with collagenous and diversion colitis has been described, however the vast majority of cases are characterised by histologically normal mucosa and are asymptomatic. 1-3 The overriding theory is that these lesions represent mucosal 'breaks' due to barotrauma from air insufflation during colonoscopy. The predominance of 'cat scratch' lesions in the right colon, where the mucosa is less compliant and more susceptible to trauma, 4 supports this hypothesis. 1-5 The presence of collagenous colitis may contribute to the risk of barotrauma by further increasing the rigidity of the subepithelium. 2 Interestingly, in all previously reported cases of 'cat scratch colon' air insufflation was used during colonoscopy and it has been postulated that the use of carbon dioxide might reduce the high pressures which cause the barotrauma. 5 We describe the first case of 'cat scratch colon' identified using carbon dioxide insufflation, during a non-traumatic procedure on a background of a histologically normal colonic mucosa.