The formation of a pelvic ileal reservoir or pouch for patients requiring a proctocolectomy for ulcerative colitis or familial adenomatous polyposis (FAP) has gained rapid favour over recent years. The operation has evolved by empiric practice with the progressive refinement of operative technique. There is still debate over whether to retain or remove the anal transitional zone (ATZ). This debate relates to concern about the neoplastic and inflammatory potential of diseased mucosa if retained in the anal canal. Similarly the chronic inflammatory changes observed in ileal pouch mucosa have raised the possibility that neoplasia may be a long term consequence of forming the ileum into a pouch. This thesis investigates these issues.
The work begins with a review of the literature on the ATZ and its importance in restorative proctocolectomy. Following this a detailed study of the micro anatomy of the anal canal is carried out on 28 anal canals. The median span of the ATZ was found to be only 4.5 millimetres and it contains almost no columnar epithelium. However an important area termed the columnar cuff was identified. In a patient who does not have a mucosectomy, the columnar cuff constitutes a span of diseased Columnar epithelium extending over 1 5 to 2.5 cm in the upper anal canal. Long term concerns need to focus on the columnar cuff rather than the ATZ.
The columnar cuff and ATZ in 113 patients with an ileal pouch has been studied. These patients had an examination with the intention of biopsying the anal canal and ileal pouch to study the ATZ and columnar cuff. It was possible to obtain a successful biopsy of the columnar cuff in 72% of cases. The technique of staining for the small bowel brush border enzyme sucrase isomaltase has been developed and shown to reliably distinguish between pouch mucosa with villous atrophy and columnar cuff mucosa. The same group of patients was followed over a 2.5 year period and 9% were shown to have symptomatic ‘cuffitis’. A histological scoring system is described and a diagnostic triad of symptoms, endoscopic inflammation and acute inflammation on histology is put forward as a way to diagnose cuffitis. The same 113 patients had columnar cuff biopsies examined for dysplasia and aneuploidy at a mean of 2.5 years after pouch formation and 10.1 years after the diagnosis of ulcerative colitis. No dysplasia was found but one patient had aneuploidy in the columnar cuff.
The final part of the work focuses on investigating the risk of neoplasia in ileal pouches. This work draws on a large cohort of 1221 patients with an ileal pouch and selects out a potentially higher risk group for pouch neoplasia. 106 patients who had a pouch for ulcerative colitis were selected, including 34 with chronic pouchitis. In addition 33 patients who had a pouch for FAP were studied. In the ulcerative colitis group one patient was found to have low grade dysplasia and aneuploidy and a further two patients aneuploidy. The risk of neoplasia in an ileal pouch for ulcerative colitis appears low and chronic pouchitis was not identified as a particular risk factor. In contrast adenomatous polyps were found in the ileal pouch of 42% of patients with FAP. It appears that forming the terminal ileum into a reservoir promotes the formation of ileal polyps.
In conclusion forming the ileum into a pelvic reservoir to maintain continence appears to be a safe procedure with medium term follow up. It will be important to continue to gather data to establish the natural history of an ileal pouch. In the interim a level of follow up and surveillance for some groups of patients may be wise. / Whole document restricted, but available by request, use the feedback form to request access.
| Identifer | oai:union.ndltd.org:AUCKLAND/oai:researchspace.auckland.ac.nz:2292/5495 |
| Date | January 2003 |
| Creators | Thompson-Fawcett, Mark W |
| Publisher | ResearchSpace@Auckland |
| Source Sets | University of Auckland |
| Detected Language | English |
| Type | Thesis |
| Rights | Whole document restricted but available by request. Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: the author |
| Relation | PhD Thesis - University of Auckland, UoA1217852 |
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