Three of four patients with CD will undergo an intestinal resection; half of them will ultimately relapse. The extent of disease at diagnosis and the presence of perianal fistulas have an impact on the risk of surgery and the risk of postoperative recurrence. Women run a higher risk of postoperative recurrence than men. The frequency of surgery has decreased over time, but the postoperative relapse rate remains unchanged.

suMMARY During the period 1955 to 1974 inclusive, 826 patients developed Crohn's disease and were registered citizens of Stockholm County at the time of definite diagnosis. These patients were followed up and investigated with reference to the occurrence of and outcome after treatment for anal fistulae. These fistulae were recorded in 184 patients (23 %/.). The incidence of anal fistulae increased the further distally the intestinal lesion was located. Healing followed local operation for anal fistula before curative intestinal resection in approximately 60% of the patients with small intestinal and combined ileocolic disease. However, patients with colonic Crohn's disease did not heal after such treatment. When curative intestinal resection was the primary procedure, 47 % of the patients healed spontaneously. Small intestinal and combined ileocolic disease was associated with a good prognosis-90 % were healed at follow-up,

SUMMARY A retrospective cohort of 823 patients with ulcerative colitis who resided at the time of diagnosis in one of three defined geographical areas (West Midlands region, Oxford region, England and Stockholm County, Sweden) was assembled. The patients were first seen at named hospitals in these areas and the diagnosis of ulcerative colitis established within five years of onset of symptoms between 1945-1965. All patients were 15 years of age or more at onset of disease and were followed for a minimum of 17 years and a maximum of 38 years. Ninety seven per cent completeness of follow up was achieved. Examining the colorectal cancer risk in the series relative to the risk in the general population by standardised morbidity ratios, there was an eight fold increased risk of cancer in the series as a whole. Dividing the series by extent of colitis, extensive colitis patients showed a 19 fold increase in risk. A four fold increased risk was shown in the remainder of the series (left sided colitis, proctitis and extent unknown). Life table analyses in extensive colitis gave cumulative risks of 7*2% (CI 3-6-10-8) at 20 years from onset of disease and 16-5% (CI 9.0-24.0) at 30 years from onset. No significant effect of age at onset, sex or referral centre could be detected. Examination of the data by interval from onset to cancer and by actual age at development of cancer suggests that patients who develop colorectal cancer will do so in a distribution around 50 years of age independent of duration of disease in adult onset ulcerative colitis (>15 years at onset of disease). An inverse relationship was shown between age at onset of disease and interval from onset of disease to cancer. Further age specific rates for cancer increased up to 50 years and decreased thereafter. These results suggest that extensive colitis patients have a genetic predisposition to colorectal cancer and that longstanding inflammation is not of prinwary importance in the initiation/promotion of cancer in this disease.There is convincing evidence from previous studies more likely to be the result of selection biases that patients with ulcerative colitis have a higher inherent in these series rather than any real differincidence of colorectal cancer than the general ences in the underlying cancer incidence of the population.' This increased incidence occurs pre-groups under review. dominantly in patients with longstanding extensive colitis. Many previous estimates of the colorectal Methods cancer incidence have been based on information drawn from hospital series of patients (Table 1) groups of patients are only found in hospitals special-

AIM:To determine whether visceral fat reduction in connection with bariatric surgery could improve weight loss and metabolic profile of obese subjects. PATIENTS AND METHODS: In a one-center, randomized and controlled pilot trial we assigned 50 subjects with severe obesity (body mass index >35 kg=m 2 ) to either adjustable gastric banding (AGB) alone (11 men and 14 women), or AGB plus surgical removal of the total greater omentum (11 men and 14 women). The patients were followed at regular intervals for 2 y and examined at 0 and 24 months with respect to body composition and metabolic profile. RESULTS: No significant differences between control and omentectomized patients were observed at baseline. The removed greater omentum constituted 0.8 AE 0.4% (mean AE s.d.) of total body fat. At 2 y follow-up there was an expected decrease in body weight and an improvement in metabolic profile in both groups. Although omentectomized subjects tended to lose more weight than control subjects the difference was not statistically significant and changes in waist-to-hip ratio and saggital diameter did not differ between groups. However, the improvements in oral glucose tolerance, insulin sensitivity and fasting plasma glucose and insulin were 2 -3 times greater in omentectomized as compared to control subjects (P from 0.009 to 0.04), which was statistically independent of the loss in body mass index. No differences in blood lipids between the groups were recorded. No adverse effects related to omentectomy were observed. CONCLUSIONS: Omentectomy, when performed together with AGB, has significant positive and long-term effects on the glucose and insulin metabolic profiles in obese subjects.