A classification of anal fistulas is presented, which is the result of an analysis of 400 cases treated over the past 15 years, based on the pathogenesis of the disease and the normal muscular anatomy of the pelvic floor. Four main types were found but numerous variations of each occur, which are described. It is hoped that this will alert the surgeon to the various complex situations that he may encounter.

Although the reduction in CRC mortality was sustained, further follow-up of the screened population has not shown a significant reduction in the CRC incidence. Moreover, despite the removal of many large adenomas there was no reduction in the incidence of invasive cancer which was independent of sex and site of the tumour.

Background: Three large randomised trials have shown that screening for colorectal cancer using faecal occult blood (FOB) tests can reduce the mortality from this disease. Two national pilot studies have recently been launched in the UK to investigate the feasibility of population screening for colorectal cancer in the National Health Service. The largest of the randomised trials was conducted in Nottingham and randomised 152 850 individuals between the ages of 45 and 74 years to receive biennial Haemoccult (FOB) test kit (intervention group) or to a control group. Aims: We have compared the mortality in the intervention group compared with the control group. Methods: The 152 850 randomised individuals were followed up through local health records and central flagging (Office for National Statistics) over a median follow up period of 11 years. Results: At a median follow up of 11 years there was a 13% reduction in colorectal cancer mortality (95% confidence interval 3-22%) in the intervention group despite an uptake at first invitation of only approximately 50%. The mortality reduction for those accepting screening was 27%. The reduction in mortality was independent of sex and site of tumour. There was no significant difference in mortality from causes other than colorectal cancer between the intervention and control groups. Conclusions: Although the reduction in colorectal cancer mortality was sustained, further follow up of this population is required to determine whether a significant reduction in the incidence of colorectal cancer will be achieved.

Aims-To determine the harm that ensues from faecal occult blood (FOB) screening for colorectal cancer. Methods-150 251 people were randomly allocated either to receive biennial Haemoccult FOB tests (n =75 253) or not to be contacted (n=74 998). Study group patients returning positive tests were oVered colonic investigation; 1774 underwent complete investigation of the colon. Results-There was no significant diVerence in the stage at presentation of interval versus control group cancers. Survival in the interval cancer group was significantly prolonged compared with the control group. Sensitivity for colonoscopy or flexible sigmoidoscopy and double contrast barium enema (DCBE) was 96.7%. There were no complications of DCBE but seven (0.5%) complications of colonoscopy, of which six required surgical intervention. There were no colonoscopy related deaths. No patients without colorectal cancer died within 30 days of colonic investigation. Five patients died within 30 days of surgery for screen detected colorectal neoplasia and a further two died without having surgery. Six patients died after 30 days but within two years of surgery for screen detected benign adenomas or stage A cancers; in all cases the cause of death was not related to colorectal cancer. Conclusions-There was investigation related morbidity but no mortality and little to support overdiagnosis bias. The group returning falsely negative tests had a better outcome compared with the whole control group. There is a negative side to any screening programme but mortality reduction in this and other trials suggests that a national programme of colorectal cancer screening should be given consideration. (Gut 1999;45:588-592)