Localisation and lesion recognition at Colonoscopy


  • The ileo-caecal valve is the only definite anatomical landmark in the colon. It may occasionally be difficult to find
  • The internal appearance of transverse colon is usually triangular. However the descending colon may look triangular or the transverse colon may look circular
  • There may be bluish/grey indentation from the liver at the hepatic flexure; however a similar appearance may sometimes occur at the splenic flexure.
  • The distance of the lesion should only be mentioned on withdrawal. So you could say that the lesion/polyp was at 30cms in the sigmoid colon on withdrawal. The scope distance information at insertion is meaningless due to the elasticity of the colon
  • For the above difficulties of localisation, any area which may need repeat inspection or treatment should be tattooed.

Lesion recognition

  • Normal colonic mucosa shows a fine, ramifying vascular pattern.
  • Mucosal lesions- The vascular pattern is lost in marked hyperaemia as in IBD.
  • There are 9 different endoscopic indices of activity for ulcerative colitis (UC) developed for clinical trials; none have been validated. All 9 indices are subject to interobserver variation (IOV).
  • Feagen score for assessing severity of colitis
    Stage 1- Granular, hyperaemic mucosa, vascular pattern not visible, not friable
    Stage 2- above plus friability (bleeds on contact, but not spontaneously)
    Stage 3- above plus spontaneously bleeding
    Stage 4- Above plus clear ulceration
    Whenever describing a colitis mention at least the extent, whether circumferential or not, friability and presence of ulceration.
  • The typical endoscopic features of Crohn’s disease are the discontinuos spread of the disease, lesions are distributed asymmetrically. There may be bizarre, ‘map-like’ necroses and fissures. Appearances of so called ‘snail tracks’, aphthoid ulcers etc
  • Malignant polyp- is suspected if the polyp is irregular, ulcerated or thick walled. Firmness to palpation with a snare tube is probably the best discriminant for a malignant polyp. If malignancy is suspected, transect low in the stalk and tattoo the area.
  • Carcinomas are usually obvious.
  • Pseudomembranous colitis- typical membrane like deposits.

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