Pathology of IBD

Bryan Warren

Powerpoint File

This talk will concentrate on clinicopathological decision making and the pitfalls encountered in assessing a patient for restorative proctocolectomy.

The precise clinicopathological diagnosis of the subtype of chronic inflammatory bowel disease of the colon has always been important for patient prognosis. The introduction of restorative Proctocolectomy made careful diagnosis and patient selection crucial to successful outcome of pouch surgery.

More recently new biological therapies may be both specific for Crohn’s disease or ulcerative colitis and quite toxic for the patient. A definitive biopsy diagnosis of Crohn’s disease often remains difficult. Crohn’s disease after treatment may mimic ulcerative colitis and vice versa. The role of the pathologist in restorative proctocolectomy varies with the procedure. In particular whether it is a one, two or three stage pouch procedure. Pathologist in the have a much easier time than those involved in the one or two stage pouch procedure. In the one or two stage pouch procedure complex clinicopathological decisions are made based on biopsy material which may be more challenging if the biopsies are from unknown sites, a limited number of sites or are viewed in isolation, without knowledge of the endoscopic appearances or the complete history. Biopsies may also present a challenge after treatment as mentioned above. The ideal starting material should be a colonoscopic report and pictures and adequate biopsies from clearly labelled sites around the colon prior to treatment. This is not always available!

The three stage restorative proctocolectomy permits several advantages. The pathologist is able to study all previous biopsy series plus a colectomy specimen. He may then have the added bonus of biopsies form a diverted rectum, and hopefully the reassurance of the appearances of the resected diverted rectum and ileostomy end. There are still pitfalls. In particular the effects of diversion of the faecal stream in ulcerative colitis include the development of histological changes, which may mimic Crohn’s disease. Important varieties of ulcerative colitis, which may mimic Crohn’s disease, are very important to recognise here. These include skip lesion sin ulcerative colitis. There are two acceptable examples of these one is in the caecum; the other is in the appendix. They do not seem to be contraindications to pouch surgery. After treatment, some cases of ulcerative colitis develop rectal sparing or more commonly relative rectal sparing which may also provide a mimic of Crohn’s disease. Ulcerative colitis after treatment may also become very patchy microscopically which may confuse on biopsy series. Accurate diagnosis and careful patient selection depend on considered clinicopathological assessment and there may be a good case for the establishment of Inflammatory Bowel Disease focussed Multidisciplinary Team Meetings similar to those, which we have for colorectal caner.

General reading:

Jewell DP, Warren BF, Mortensen NJ. Challenges in Inflammatory Bowel Disease. Blackwell. 1sst edition 2001. 2nd edition due 2006.

Warren BF, Shepherd NA. Surgical pathology of the intestines: the pelvic ileal reservoir and diversion Proctocolitis. In; Lowe DG, Underwood JCE Eds. Recent Advance in Histopathology Vol 18; Edinburgh, Churchill Livingstone, 1999; 63-88

Warren BF, Shepherd NA. The role of pathology in pelvic ileal reservoir surgery. Int J Colorectal Dis 1992; 7: 68-75.