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This presentation assesses the incidence of perforation of the intestine in patients with inflammatory bowel disease by reviewing the incidence of this complication in a total of 3175 patients from the OMGE inflammatory bowel disease multi-national survey. Amongst 1928 patients with ulcerative colitis, perforation was noted in only 5 (0.3%), which is much lower than in previous series (from 1% to 2%). By contrast, 19 of 1247 patients with Crohn's disease had perforated (1.5%). The survey thus suggests that the incidence of perforation in ulcerative colitis has fallen in the last 2 decades, probably as a result of the widespread implementation of early surgery. The risk of perforation of Crohn's disease remains quite high.

This presentation describes the progress during 1978-1982 of the O.M.G.E. Multinational Survey of patients with inflammatory bowel disease. After a brief description of the study design and protocol, and review of results up to 1978, the status of the survey in 1982 is presented. In all, 35 centres contributed 2,657 cases at that time; data collection being meticulous via previously designed proformata. Diagnostic criteria are next discussed. Little change between 1978 and 1982 is noted, with wide variation in the UC/CD ratio for individual centres, but continuing evidence of a congruence of diagnostic thought, now codified into a simple (and recommended) O.M.G.E. Scoring System. Patients seen prior to 1978 were reviewed in 1982. Where attempted, a follow-up of over 90% was achieved, usually more than four years after the original presentation. Interesting data resulted. The stability of diagnosis was high, only 3.4% of patient diagnoses changing between 1978 and 1982. The mortality of Crohn's disease patients, usually unrelated to surgery, was higher than that of ulcerative colitis patents, and the cancer risk identical in the two groups. Most patients were well at review; but--though asymptomatic--were usually on prophylactice therapy, most commonly with salazopyrine. Finally, problems in assessing severity and activity of disease are discussed, and joint studies between O.M.G.W. and the newly formed International Organisation for the Study of I.B.D. described. As regards Crohn's disease, several 'indices of activity' already exist; when tested on a set of 200 O.M.G.E. patients, indices did not correlate well with each other, or with patient prognosis. Further studies are suggested during 1982-1986.

Inflammatory bowel disease is being studied by the World Organisation of Gastroenterology (OMGE) Research Committee in a survey (currently) affecting 1696 patients presenting to 30 hospitals in 16 countries. A computer-aided diagnostic prediction system (when tested in 1056 patients) showed an accuracy of match between computer prediction and clinical diagnosis in 94% of these patients. Most centres, however, do not possess appropriate computing facilities. A simple diagnostic "scoring system", based on likelihood ratios, has therefore been developed, using a series of numbers set out on a single sheet of paper. The overall accuracy of the simple scoring system in the same 1056 patients was equivalent (93%) to the computer-aided system. In a further series of 510 "new" patients from eight fresh centres the diagnostic scoring system made a firm prediction in 490 cases (96%). Where made, the accuracy of match between the scoring system prediction and clinical diagnosis was 96%. It is suggested that this simple system, which requires no analytical resource and could be used by any gastroenterologist, might be of some value in clinical research and clinical practice.

This paper assesses the extent and importance of geographical variation in disease presentation in relation to automated systems for clinical decision making. Reference is made to studies carried out by the World Organization of Gastroenterology involving 1,500 patients with inflammatory bowel disease, 6,000 patients with acute abdominal pain, and 1,300 patients with upper GI bleeding. These studies indicate that geographical variation in disease presentation (both regarding prior probability of disease and conditional probability of symptoms in each disease) is so great as to constitute a considerable potential threat to the widespread introduction of any automated decision-making system. It is suggested that there is an urgent need for the creation of large-scale multinational case series where diseases and symptoms are adequately and reproducibly defined in advance. Reference to studies previously mentioned is used to adduce evidence of the benefits of such large-scale data bases.

There is no room for complacency concerning our knowledge of Crohn's disease of the colon, and this applies to epidemiology as to other aspects of diagnosis and management. In this presentation therefore "current knowledge" is first reviewed. Crohn's disease of the colon is shown to be a worldwide disorder with incidence rates of between one and four cases per 100,000 population per year and prevalence rates up to ten times this figure. This disease is most commonly found in Europe and North America, with a slight excess in females over males and a preponderance of young persons whose disease begins in early adult life. Two-thirds of cases have colonic involvement. Racial and ethnic studies have been confusing and there is some reason to doubt the simplistic assertion of the 1960's that the disease is most common in Jews. Genetic marker studies have been similarly inconclusive despite an apparent association with HLA-B27-as have most studies involving environmental factors such as diet, smoking and the contraceptive pill. The presentation next explores some important reasons why this current "knowledge" is suspect as well as inconclusive. There is a total lack of etiological data about Crohn's disease, and until recently no standard definition of the disease existed. Many epidemiological studies have selected cases from small groups rather than the whole population-a particularly difficult problem due to the protean nature of the disease. Observer variation in eliciting data presents a further problem as does the simplistic nature of the analysis carried out to date. Finally, some tentative solutions are proposed for current outstanding problems. It is argued that Popperian philosophy may form the basis for a working description of Crohn's disease and the World Organisation of Gastroenterology Crohn's disease study has proposed such a definition. Multi-national trials are clearly necessary if some of the problems listed earlier are to be overcome; as is the development of reproducible and relevant indices for assessing the severity of disease. However, in the last analysis the only real key to progress is an improvement in our fundamental understanding of the disease itself; and at the present time there seems very little prospect of progress on this front. Until such progress is made, the epidemiology of Crohn's disease will remain a difficult and muddled area.

An analysis is presented of the course and outcome of the initial referred attack in a group of 332 patients with Crohn's disease treated at the General Infirmary at Leeds from 1939 to 1968 inclusive. A further 50 cases were excluded on the basis of insufficient diagnostic evidence: usually such patients had acute terminal ileitis. Only 5% of patients achieved full remission on conservative management, and most eventually came to surgery. The overall fatality rate was some 3.3% and this was affected chiefly by the severity of attack and the age of the patient. The severity of attack was classified as mild, moderate, or severe according to a system which took into account factors such as bowel habit, rectal bleeding, abdominal pain, pulse rate, temperature, haemoglobin, and weight. In attacks graded as ;mild', no deaths occurred; in those graded ;severe' the fatality rate was 8.8%. Similarly, whilst no patient under 20 years of age died, the fatality rate in the over 60s was some 14.8%. Further comparison between the present group of 332 patients and an earlier series of 204 patients suffering from ulcerative colitis (Watts, de Dombal, Watkinson, and Goligher, 1966a) shows considerable differences in the course and prognosis of the two diseases. In particular 70% of patients with ulcerative colitis achieved remission on conservative management alone whereas only 5% of Crohn's disease patients did so. These differences, and in particular the poor response to conservative therapy, are discussed, together with their implications for management.

This presentation reviews the course and outcome of disease in 2657 cases of inflammatory bowel disease (IBD) registered into the OMGE multinational survey and considers whether there are differences between the natural history of IBD observed in this series and that observed in earlier large-scale series. It is concluded that several such differences exist. The current mortality from ulcerative colitis (4% in 10 years) is similar to that from Crohn's disease and quite different from that recorded in earlier series (over 20% in 10 years). This may be because the disease itself has changed (the proportion of patient-years with severe attack has fallen from 14.6% in the 1960s to under 10% in the present series). It may also be because of increasing use of maintenance sulphasalazine (since the attack rate per year is significantly lower than patients on maintenance therapy). Finally, cancer is now equally common in Crohn's disease and ulcerative colitis patients; whilst perforation is more common in Crohn's disease (possibly because ulcerative colitis patients now tend to come to surgery earlier).

This presentation describes the progress during 1982-1986 of the OMGE Multinational Survey of patients with inflammatory bowel disease. After a brief description of the study design and protocol, the status of the survey in 1986 is presented. In all, 40 centres contributed 3175 cases at that time, data collection being meticulous via previously designed proformata. Diagnostic criteria are next discussed. Little change between 1976 and 1986 is noted, with wide congruence of diagnostic thought, now codified into a simple (and recommended) OMGE diagnostic scoring system. Patients seen prior to 1978 were reviewed in 1986. Where attempted, a follow-up of over 86% was achieved, usually more than 4 years after the original presentation involving no less than 5215 'patient-years' of observed follow-up. Following these overall considerations, details of four subprojects are annexed, each of which was presented as a 'free paper' at the 8th World Congress and concerning, respectively, the changing natural history of IBD, risks of perforation and toxic megacolon in the 1980s, IBD in elderly patients, and features associated with recurrence in Crohn's disease.

The prospect of recurrence following surgery for Crohn's disease (CD) poses an important and difficult problem in routine clinical practice. Out of the 1247 CD patients registered in the OMGE multinational inflammatory bowel disease survey, a high proportion came to surgery. A detailed study has been undertaken of 154 patients (77 who did recur matched with 77 who did not recur) who had undergone surgery for CD. An assessment was made which established a 'risk factor' (RF) for each item of patient information. Findings indicated the risk of recurrence to be higher in patients under 20 years both at onset of disease (RF, 2.2:1) and at time of their operation (RF, 2.7:1) and in patients with distal colonic Crohn's disease (RF, 1.8:1). Histopathologic findings, number of previous operations, and symptomatic status prior to operation did not appear to affect the subsequent risk of recurrence. The margin of clearance at operation appeared to affect further recurrence. Amongst patients with 10cm or more margin of clearance (i.e. histopathologically normal bowel) only 21% recurred during follow-up, versus 50% in those with a smaller margin of clearance.

Studies of inflammatory bowel disease (IBD) undertaken in the 1960s reported a highly unfavourable course and prognosis in patients over the age of 60 years. However, recent surveys have suggested that the pattern of IBD in the elderly patient is similar to the overall pattern of disease in other age groups. We have, therefore, reviewed data relating to 2657 patients from the OMGE series with particular reference to the pattern of disease in 244 patients (9.1% of the total group) aged over 60 years at the time of registration into the survey. The course and outcome of disease in these 244 patients were similar to other age groups in terms of response to therapy, major complications, and rate of recourse to surgery. However, the death rate in the elderly (2.4%) was higher than that in younger patients (0.8%). We concur with recent studies that the course of IBD is now more favourable in elderly patients than hitherto suspected. The cause is probably multifactorial, involving both a change in therapy and a change in the natural history of the disease.

Observer variation in calculating various indices for estimating the severity and activity of Crohn's disease is reported. Seven prospective users of Crohn's disease activity indices were presented with 10 'cases histories' compiled from relevant patient data and asked to calculate (independently) various indices of severity and activity from this information. The results showed a disquieting degree of observer variation in all indices studied. Similar results were obtained when 15 members of the International Organisation for the Study of Inflammatory Bowel Disease (IOIBD) reviewed one case history and also when members independently reviewed a series of real life cases. It is suggested that each index so far proposed is open to considerable observer variation, which casts some doubt upon the validity of studies so far carried out. Clarification of indices and the use of ranking methods can, however, do much to overcome this discrepancy.

The problems associated with recurrent Crohn's disease were examined in a series of 168 patients who had undergone primary resection for this condition at the General Infirmary at Leeds from 1939 to 1968 inclusive. The overall recurrence rate was 34.2%. The risk of recurrence was less in patients with involvement mainly of large bowel rather than small. It was also affected by the age of the patient, being greatest in children or adolescents, less in adults, and least in those over 60 years of age. Recurrent disease was most commonly found in the small bowel proximal to an anastomosis, and usually manifested itself either in the first year or two after surgery or some five to 15 years later. Patients with ;early' recurrence had a shorter history of symptoms at operation, and a graver outlook than those with ;late' recurrence. The status of recurrent cases was much better than might have been anticipated in so far as nearly 70% of them were considered at review to be in very good or good general health. Moreover the risk of further recurrence after a second or third operation was found to be no greater than after a first operation.

This paper reports the outcome of 60 pregnancies in 40 women, all of whom had concomitant Crohn's disease. Detailed analysis of pregnancy rates in Crohn's disease supports in outline the hypothesis that some patients with bowel symptoms may be rendered temporarily subfertile by the activity of their bowel complaints. In contrast there is little or no evidence of any adverse effect during pregnancy on mother or child. Most pregnancies went normally to term and, if anything, Crohn's disease tended to improve during the period of confinement.After delivery, however, over 40% of patients suffered a relapse of Crohn's disease. Such a situation might well constitute a logical indication for the administration of corticosteroid therapy.