THE HISTOLOGICAL PATTERN AND PATHOLOGICAL INVOLVEMENT OF THE ANAL TRANSITION ZONE IN PATIENTS WITH ULCERATIVE-COLITIS

Background: The aim was to determine whether the transitional epithelium (TE) of the anal transition zone (ATZ) was involved by chronic ulcerative colitis (CUC) and whether preserving the ATZ preserves the disease. Methods: Proctocolectomy specimens from 50 CUC patients and 50 patients with rectal cancer serving as controls were stained with alcian-blue to map the ATZ, and biopsy specimens containing adjacent TE and rectal mucosa were examined. Results: The mean inflammation score (0, none; 4, severe) in TE of controls was 0.4, whereas in CUC it was 0.5. However, the mean inflammation score of the rectal mucosa within the ATZ was 0.2 in controls and 2.6 in CUC (P < 0.001). Rectal columnar epithelium extended past half of the maximum length of TE in 75% of patients (65-83%; 95% CI) and was within 1 cm of the dentate line in 89% (81%-94%). Conclusions: Although the TE of the ATZ was not inflamed, the rectal mucosa within the ATZ was. Moreover, rectal mucosa traversed half of the length of the ATZ in 75% of patients and was within 1 cm of the dentate line in fully 89%. Preserving the ATZ may preserve the disease in the majority of patients with CUC. © 1993.