Evolution of the changes of the ileal pouch mucosa over a long follow-up period

The mucosa of the ileal pouch after restorative proctocolectomy develops relevant adaptative changes but the real mechanisms and the evolution over time of these alterations are still unclear. The aims of the present work were to study the distribution of the mucosal changes at different levels in the reservoir and to evaluate the evolution of these alterations over a long follow-up period.

The severity of chronic and acute inflammation, villous atrophy, colonic-type mucins production and proliferative index were evaluated in the bioptical specimens from 46 patients (30 males, 16 females, mean age 38 years) with functioning pouch. We compared the histology of the upper pouch mucosa with the lower one. Then we divided the 46 patients into Group A-24 patients with a median follow-up of 11 years (range 9-16); Group B-22 patients with a median follow-up of 4 years (range 2-8), comparing the results from the two groups. Finally we performed a prospective evaluation in the 24 patients who were controlled in 3 subsequent follow-ups (1993-1994, 1996-97, 1999-2000).

At the topographic evaluation only the acute inflammation was significantly more pronounced in the lower pouch area (p = 0.031). All the morphological changes showed a trend of greater severity in the group A patients, in particular villous atrophy (p = 0.005) and colonic-like mucins secretion (p = 0.006). At the prospective evaluation, the chronic inflammation showed a significant progressive worsening over time (p = 0.011).

Our experience showed that the transformation of the mucosa represents an "organ" response to the luminal environment and may progress over time.