Biomedical subjects
Publications and source records attributed to R N Allan.
A previously fit 23 year old adult male who presented with a sudden onset of profound autonomic neuropathy, for which no cause could be found, is described. The patient subsequently developed ischaemic enterocolitis that ultimately necessitated colectomy and subtotal enterectomy. Potential neural and humoral mechanisms are discussed.
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The course, prognosis and management of 62 patients with Crohn's disease aged 55 years or over at diagnosis has been reviewed. The distal ileus was the commonest site of disease in the older patient, where the characteristic presentation was acute after initially mild symptoms. Early local resection was often required, particularly where there was diagnostic doubt or suspicion of caecal malignancy. Recurrence rates were much lower in the older patient than after resection in younger patients. Medical treatment played a minor role in the management of patients with distal ileal disease, in part because stricture formation was present at diagnosis and the acute nature of symptoms at presentation led to early surgical treatment. Colonic Crohn's disease was usually confined to the distal or left side of the colon and initially could be difficult to distinguish from diverticular disease. Extensive colonic Crohn's disease was rare. The apparently limited disease was not necessarily associated with a good prognosis, since disease at this site sometimes progressed rapidly, necessitating urgent surgical resection. Medical treatment (corticosteriod therapy, with or without azathioprine) was usually effective initially for treatment of symptomatic colonic Crohn's disease, but sustained remission was rare. Those patients with persistent symptoms were restored to good health with surgical treatment but at a price, in that nearly half eventually required a permanent stoma.
Until recently the investigation of serological responses to mycobacteria in patients with Crohn's disease has been hindered by the considerable degree of cross-reactivity between antigens of M. paratuberculosis, and other mycobacterial subspecies. We evaluated the serological response of Crohn's disease patients to a recently identified species-specific 18 kDa protease-resistant antigen corresponding to M. paratuberculosis bacterioferritin. The 18 kDa antigen was purified from M. paratuberculosis as previously described. Serum was obtained from 40 patients with Crohn's disease, 15 with ulcerative colitis, 25 coeliac patients, and 21 normal blood donors. Antibody levels were measured by enzyme-linked immunosorbent assay (ELISA), with anti-human IgA and IgG alkaline phosphatase conjugate. Antibody titres were expressed as the dilution giving 1/3 of the plateau binding value of a standard positive serum (MT/3). Disease activity of the Crohn's disease cases was assessed using the Harvey-Bradshaw index. There was no statistically significant elevation of the mean IgG or IgA MT/3 titres of Crohn's disease patients over controls. No patients had antibody titres greater than two standard deviations above the mean control MT/3 titres, and there was no significant correlation between Crohn's disease activity and level of antibody titres. These findings make it unlikely that M. paratuberculosis is of primary pathogenic importance in Crohn's disease.
OBJECTIVE: To assess the changing distribution of disease within the large bowel in patients presenting with ulcerative proctitis or proctosigmoiditis. To evaluate the influence of clinical exacerbations, smoking, parity and family history in disease extension. DESIGN: Retrospective single-centre study in a university hospital. METHODS: Case records of patients presenting over a 40-year period were examined to evaluate the clinical course and disease distribution from initial presentation to final follow-up. For each patient whose disease extended to the more proximal colon, an age- and sex-matched control patient was identified whose disease remained confined to the original site. Patients completed a questionnaire to provide information on family history, smoking and parity. The differences in clinical exacerbations, family history, smoking and parity were then compared between the two groups. RESULTS: Among 145 patients presenting with proctitis or proctosigmoiditis followed prospectively for a median period of 10.9 years, the disease extended in 53 patients. Using actuarial methods the disease progressed beyond the rectosigmoid area in 16% of patients at 5 years and 31% at 10 years. Among the patients whose disease progressed, progression was preceded in 68% of cases by a clinical exacerbation of the colitis. When patients whose disease progressed were compared with those whose disease remained confined to the original site, no differences were detected in the number of clinical exacerbations, smoking habit, family history or parity. CONCLUSIONS: The factors that are associated with the extension of colitis are probably different from those that predisposed an individual to develop inflammatory bowel disease initially.
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We report a case of bilateral endogenous Escherichia coli endophthalmitis in an insulin-dependent diabetic. This condition appears to occur almost exclusively in diabetics, and is invariably related to a urinary tract infection. Treatment of any infection in diabetics should be aggressive, and any deterioration in vision should be addressed promptly.
Three patients with Crohn's disease are described who were treated by ileal resection for intestinal obstruction. Histological examination of the resected specimen in each case established the diagnosis of adenocarcinoma of the small intestine complicating Crohn's disease. This diagnosis should be considered in patients with longstanding macroscopic Crohn's disease who present with severe or recurrent symptoms. The diagnosis may not be apparent on routine radiological examination or even macroscopically at laparotomy.
The increased prevalence of gall stones in Crohn's disease is thought to be related to depletion of the bile salt pool due either to terminal ileal disease or after ileal resection. This study was designed to examine whether this hypothesis is correct and explore alternative explanations. Two hundred and fifty one randomly selected patients (156 females, 95 males, mean age 45 years) were interviewed and screened by ultrasonography to determine the prevalence of gall stones in a large population of patients with Crohn's disease. Sixty nine (28%) patients had gall stones proved by ultrasonography (n = 42), or had had cholecystectomy for gall stone disease (n = 27). The risk factors for the development of gall stones including sex, age, site, and duration of disease, and previous intestinal resection were examined by multivariate analysis. Age and duration of disease were positive risk factors for gall stones and were covariables. The site of disease and of previous intestinal resection did not predispose to gall stones. Previous surgery was an independent risk factor for the development of gall stones, the risk increasing with number of laparotomies. It is suggested that mechanisms other than ileal dysfunction may predispose to gall stones. Postoperative gall bladder hypomotility with biliary sludge formation may be precursors of gall stone formation in patients with Crohn's disease.
The risk of developing colorectal cancer has been compared in two identically selected cohorts of patients with extensive Crohn's colitis (n = 125) and extensive ulcerative colitis (n = 486). In both groups the effects of selection bias have been reduced wherever possible. There was an 18-fold increase in the risk of developing colorectal cancer in extensive Crohn's colitis and a 19-fold increase in risk in extensive ulcerative colitis when compared with the general population, matched for age, sex, and years at risk. The absolute cumulative frequency of risk for developing colorectal cancer in extensive colitis was 8% at 22 years from onset of symptoms in the Crohn's disease group and 7% at 20 years from onset in the ulcerative colitis group. The relative risk of colorectal cancer was increased in both ulcerative colitis and Crohn's disease among those patients whose colitis started before the age of 25 years. Whether the absolute risk is greater in the younger age group or merely reflects that the expected number of carcinomas increases with age is uncertain. While there is an increased risk of developing colorectal cancer in extensive colitis the number of patients with Crohn's disease who actually develop colorectal cancer is small because many patients with extensive Crohn's colitis undergo colectomy early in the course of their disease to relieve persistent symptoms unresponsive to medical treatment.
The surgical resection rates among parous women with distal ileal and colonic Crohn's disease have been compared with resection rates among distal ileal (n = 197) and colonic (n = 332) Crohn's disease patients. Thirty of 44 parous women with distal ileal Crohn's disease and 28 of 44 with colonic Crohn's disease had achieved their first pregnancy on average 8 years and 6.2 years respectively before the diagnosis of Crohn's disease was established. Resections for each patient were negatively correlated with parity in both groups. (Distal ileal disease (p = 0.034, rs = 0.3207), colonic disease (p = 0.051, rs = -0.2960)). Patients with distal ileal Crohn's disease and a history of pregnancy at diagnosis (n = 30, mean follow up = 15 years) had fewer resections/patient when compared with the published resection group: mean (SD); 1.17 (0.65) v 1.57 (1.05), p = 0.006. Patients with colonic Crohn's disease and a history of pregnancy at diagnosis (n = 28, mean follow up = 16.5 years) had fewer resections/patient when compared with the published resection group: mean (SD); 0.68 (0.77) v 1.05 (0.77), p = 0.019. In summary, patients with distal ileal and colonic Crohn's disease, who had been pregnant in the past subsequently need fewer surgical resections. Pregnancy could influence the natural history of Crohn's disease either by decreasing immune responsiveness or by retarding fibrous stricture formation, which is the commonest indication for surgical intervention.
The colorectal cancer risk in Crohn's disease eliminating all known biases was assessed in a cohort of 281 patients with Crohn's disease who resided in the West Midlands at the time of diagnosis, and were first seen within five years of onset of symptoms between 1945-1975. All patients were 15 years of age or more at onset and were followed up from 12-35 years (total 5213 person years at risk (PYR)). The colorectal cancer risk in the series compared with the risk in the general population was computed by applying sex and age specific PYRs to the date of death or end of the study period 31 December 1991. There were six colonic and two rectal cancers. Six of the eight colorectal cancers were diagnosed 20 or more years after the onset of Crohn's disease. The relative risk (RR) of colorectal cancer for the series as a whole was 3.4 (p < 0.001), with a fivefold excess in the colon, but no significant excess in the rectum. Patients with extensive colitis showed an 18-fold increase in risk (RR = 18.2, p < 0.001), which decreased with increasing age at onset. This study shows that there is a statistical excess risk of developing colorectal cancer in patients who develop their Crohn's disease at a young age of onset (less than 30 years of age).
A 31 year old man from Gambia, resident in the United Kingdom for two years, presented with a two month history of unproductive cough, malaise, weight loss, non-specific abdominal pain, and episodic diarrhoea. Acid alcohol fast bacilli were identified in his sputum, together with Strongyloides stercoralis larvae and Giardia lamblia cysts in his stools. This case illustrates that latent strongyloidiasis can become overt in the presence of tuberculosis, and the diagnosis of strongyloidiasis must be borne in mind in patients who have previously resided in endemic regions.
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The clinical course of 44 patients undergoing elective proximal fecal diversion for Crohn's disease of the colon is reported. Sustained disease remission was obtained in 31 patients (70 percent). Diversion was associated with a significant reduction in steroid requirements (P < 0.01) and a significant improvement in hemoglobin (P < 0.001), erythrocyte sedimentation rate (P < 0.001), and albumin (P < 0.05). Sixteen patients (36.4 percent) have required a proctocolectomy, 19 patients (43.2 percent) remain defunctioned, and four patients (9 percent) have died. Five patients have had intestinal continuity restored, which has remained intact in four patients for a mean follow-up of 99 (range 21-153) months. Fecal diversion for Crohn's disease of the colon produces a high incidence of sustained disease remission, but for the majority of patients the prospect of future restoration of intestinal continuity is limited.
Diffuse jejunoileitis is an uncommon, but important manifestation of Crohn's disease because of the associated high morbidity and challenges in medical management. Despite this there have been no studies of prognosis or management of diffuse jejunoileitis for nearly 20 years. This study analysed the outcome among 34 patients (20 women and 14 men) with diffuse jejunoileitis diagnosed between 1960 and 1991 including clinical features, medical and surgical management, death rates, current status, and prognosis. Diffuse jejunoileitis presents in younger patients (mean age at diagnosis 26.4 years) than those with distal ileal Crohn's disease (mean age at diagnosis 33.3 years). Nearly all presented with clear cut abdominal symptoms including a combination of colicky abdominal pain (91%), weight loss (62%), and diarrhoea (53%). Most patients had severe symptoms reflected by the fact that 77% had been treated with corticosteroids for periods of more than six months at some stage during their follow up. The mean follow up from diagnosis was 16 years. Twenty eight patients (82%) had at least one operation for diffuse jejunoileitis and two thirds of the patients (n = 21) required two or more operations. The frequency of surgical intervention was particularly high in the younger patients (r = 0.71, p < 0.001). The proportion of patients requiring surgery was highest in the first year after diagnosis. The annual operative rate was 15% for the first 10 years and then it fell to 5.2% in years 11-15, and 2.6% in years 16-20. The data suggest that the disease does burn itself out over time. The increasing use of strictureplasty for short strictures and the minimal use of resection has eliminated problems associated with the short small bowel syndrome. The longterm prognosis of this patients is good. Only two patients died (one of perforation of the jejunum and another of an unrelated bronchogenic carcinoma). After a mean interval from diagnosis of 16 year, 24 of 32 living patients are well and symptom free. Only eight have abdominal symptoms of whom three are receiving corticosteroid treatment and one azathioprine. The combination of anti-inflammatory drugs with the relief of recurrent obstructive symptoms by strictureplasty can together produce a good longterm prognosis in most patients with diffuse jejunoileitis.
Cultural and serological studies have provided limited, often conflicting, evidence of a role for mycobacteria in the pathogenesis of Crohn's disease. Interest has focussed on Mycobacterium paratuberculosis, previously considered to be common in the environment with no major role as a human pathogen. Whether a specific serum antibody response to mycobacteria occurs in Crohn's disease or ulcerative colitis was investigated. Sera from patients with Crohn's disease (n = 38), ulcerative colitis (n = 15), and a healthy control population (n = 30) were assayed in an enzyme linked immunosorbent assay (ELISA) using eight filtered sonicate mycobacterial preparations and a purified protein derivative made from the bovine tubercle bacillus. In addition, IgG, IgM, and IgA levels to M paratuberculosis were determined in sera from patients with active (n = 24) or inactive (n = 29) Crohn's disease and the control populations. There was strong evidence of contact with environmental mycobacteria in all patients and control populations, with the greatest responses to preparations of M avium, M tuberculosis, and M kansasii. A large proportion of patients with Crohn's disease had antibodies that bound most antigens tested but there were no statistical differences between these values and those of the control population. Similarly, there were no differences in antibody levels to M paratuberculosis in patient and control groups. Although a subset of patients with active Crohn's disease (25%) had IgG concentrations that exceeded the control mean by more than 2 SD, this phenomenon may not be specific to Crohn's disease: 20% of a small group of patients with coeliac disease had similarly raised IgG levels to M paratuberculosis. These findings do not provide serological evidence of a role for this organism in the pathogenesis of Crohn's disease.
Culture studies have suggested that Mycobacterium paratuberculosis may play a role in the aetiology of Crohn's disease. However, evidence of sensitization to mycobacterial antigens amongst patients with Crohn's disease has not yet been adequately demonstrated. Previous studies of cell-mediated immunity (CMI) in Crohn's disease were restricted to responses of peripheral blood mononuclear cells (PBMC) to mycobacterial antigens. In this study we have investigated the proliferative responses of both PBMC and mesenteric lymph node mononuclear cells (MLNMC) to a range of mycobacterial and non-mycobacterial antigens. There was no evidence of specific sensitization in the responses of MLNMC and PBMC from patients with inflammatory bowel disease (IBD) to the mycobacterial antigens. However, anergy to M. paratuberculosis could not be excluded. IBD MLNMC responses to most antigens were generally greater than those of PBMC, which were often undetectable. When compared with controls, there was evidence of increased CMI to a range of non-mycobacterial antigens, especially Yersinia enterocolitica, amongst both MLNMC and PBMC from patients with Crohn's disease and ulcerative colitis (UC). These results do not provide support to the proposed role of mycobacteria in the pathogenesis of Crohn's disease, but indicate that further investigation may determine a role for bacterial-specific T cell-mediated responses in the pathogenesis of IBD.