A prospective study of diagnostic methods in adenoma follow-up

Three hundred and thirty patients having had previous colonoscopic polypectomy of adenomas were recalled for follow-up and submitted to all available diagnostic methods: occult blood testing, digital examination, rigid proctosigmoidoscopy, fibre-optic sigmoidoscopy, total colonoscopy and double contrast barium enema. Polyps up to 7 mm diameter were electro-coagulated during diagnostic endoscopy but larger polyps were left in situ for barium enema before polypectomy at a later date. Disparities between endoscopy and X-ray were rechecked by one or both procedures. Occult blood testing, digital examination and rigid proctosigmoidoscopy were found to be inaccurate or ineffective in diagnosis of the 37% of patients with further adenomas or carcinomas. Double contrast barium enema demonstrated 71% of larger lesions compared to the 92% shown by colonoscopy. The commonest sites of X-ray inaccuracy were in the sigmoid colon and caecum. Colonoscopy permits immediate electrocoagulation or snare polypectomy of any lesions seen, as well as being the more accurate investigation and is, therefore, the procedure of choice in post polypectomy follow-up. The mean time taken for diagnostic total colonoscopy in this series was 15.3 minutes, comparable to the time taken for barium enema. Postal questionnaire showed both procedures to be equally well tolerated by the patients. Thirty per cent of colonoscopies were, however, considered technically difficult by the endoscopist, and for these patients it is suggested that follow-up should be by the combination of fibre-sigmoidoscopy using carbon dioxide insufflation and immediate double contrast barium enema. Should this combination indicate a need for total colonoscopy, then almost all adenomas and cancers would be detected. Total examination of the colon by one or other means is essential, over half the patients with adenomas and three of the five patients with carcinoma showing no pathology in the territory of fibresigmoidoscopy or limited colonoscopy.