OBJECTIVE: To conduct a prospective audit of all patients presenting with anal fistula at St. Mark's Hospital during one calendar year and to compare the presentation and outcome of this cohort with previous reports from this institution. PATIENTS AND METHODS: All patients undergoing examination under anaesthetic (EUA) for anal fistula during 1997 were studied. All fistulae were anatomically classified and operative procedures recorded. During a mean follow-up period of 14 months details of healing, recurrence and function were gathered. RESULTS: 98 patients with a mean age of 43.7 years were assessed. 86 (88%) patients had fistulae of cryptoglandular (idiopathic) origin. Fistulae were superficial in 11 (11%) patients, intersphincteric in 30 (31%) patients, trans-sphincteric in 52 (53%) patients, suprasphincteric in 3 (3%) patients and extra-sphincteric in 2 (2%) patients. 49 (50%) fistulae were classified as complex. Eradication of fistulae with preservation of function was achieved in 89 (91%) patients. Fistula recurrence occurred in 4 (4%) cases. Ten (10%) patients had some degree of incontinence, 9 (9%) of whom had undergone previous fistula surgery. Nine (9%) patients still had setons in situ at the end of the follow-up period. CONCLUSIONS: A greater proportion of difficult fistulae was seen during the year compared with previous studies from St. Mark's. Despite this a satisfactory outcome was achieved in the vast majority with a relatively low rate of disturbed function. Previous fistula surgery is a risk factor for incontinence, which can usually be managed conservatively.

Adipose tissue is reported to contain monocyte-like pre-adipocytes, which may mature into macrophages, contributing to local inflammation. Dendritic cells (DC) can be derived from monocytes and initiate and regulate primary immune responses. We hypothesized, therefore, that adipose tissue may provide DC involved in local immune activity. To test this, we studied cells from human omental adipose tissue samples from 17 patients with benign gynecological disease. The hypothesis that adipose tissue DC are involved in inflammatory disease was tested by comparing these cells with those from 18 patients with Crohn's disease, where hypertrophy of adipose tissue suggests involvement in disease. A high proportion of the 1.33 +/- 0.12 x 10(5) CD45-positive cells/mg, obtained from control omenta, expressed CD11c, CD1a, and CD83; costimulatory molecules CD40, CD80, and CD86; and major histocompatibility complex (MHC) Class II but little CD14, CD16, or CD33. Omental cells showing morphological characteristics of DC were also observed. Metrizamide gradient-enriched DC from these populations were potent stimulators of primary proliferation of allogeneic T cells in mixed leukocyte reactions. Increased numbers of CD45+ cells from omentum of Crohn's patients (4.50+/-1.08 x 10(5) CD45+ cells/mg) contained higher percentages of CD11c+ and CD40+ cells (80.8+/-3.8% vs. 63.4+/-6, P=0.032; 77.9+/-4% vs. 58.8+/-6.5, P=0.029, respectively), but MHC Class II and stimulatory capacity were almost completely lost (P= <0.001), suggesting innate activation but lost capacity to stimulate adaptive immune responses. Granulocytes were also present amongst the omental cells from Crohn's patients. Results indicated that omentum may provide DC, which could "police" local infections and contribute to and/or reflect local inflammatory activity.

Site-specific differences in fatty acid composition in normal human mesentery are consistent with local interactions between lymph node lymphoid cells and adjacent adipose tissue. These site-specific properties are absent in CD, causing anomalies in composition of lymphoid cell fatty acids, which may explain the efficacy of elemental diets containing oils rich in n-6 polyunsaturates.