Colectomy with ileorectal anastomosis lowers rectal mucosal cell proliferation in familial adenomatous polyposis

Rectal polyp regression has been observed in familial adenomatous polyposis (FAP) after colectomy and ileorectal anastomosis (IRA). In view of the association between risk of neoplasia and epithelial cell turnover rates, a study was conducted to determine the effect of colectomy and IRA on rectal mucosal proliferation in FAP. Endoscopic biopsies of flat rectal mucosa were taken from 12 FAP patients with an established IRA and 10 FAP patients prior to colectomy. Mucosal proliferation was assessed by flash-labeling S-phase cells with bromodeoxyuridine. Labeled cells were visualized on paraffin sections with an immunohistochemical stain using a monoclonal antibody to bromodeoxyuridine. Twenty crypt columns were analyzed. The mean labeling index (percent labeled cells/crypt) of the FAP patients with established IRAs (7.0 +/- 1.4 percent) was significantly less than that of the precolectomy patients (12.8 +/- 3.0 percent) (Mann-Whitney U test, P = 0.0004). Comparison of labeled distribution curves shows a contraction of the crypt proliferative zone in the IRA group. Colectomy with IRA in FAP is associated with a significant reduction in rectal mucosal cell proliferation. These findings support the claim of reduced risk of rectal cancer following this procedure in FAP and are of relevance to the study of environmental vs. genetic control of cell proliferation.