ABNORMAL RECTAL MUCOSA OF THE ANAL TRANSITIONAL ZONE IN ULCERATIVE-COLITIS

Objective: To determine the frequency of atypia and active ulcerative colitis (UC) in rectal mucosa within the anal transitional zone (ATZ). Design: Surgeons identified ATZ tissues from restorative proctocolect omy specimens for determination by surgical pathologists of specific h istopathologic features in rectal mucosa of the ATZ. Setting: Surgical referral center for restorative proctocolectomy. Patients: Ninety-fou r patients with symptomatic UC underwent restorative proctocolectomy b etween January 1991 and December 1994. Interventions: Specific histopa thologic features of active UC in the ATZ were evaluated by a single r eviewer who did not know the clinicopathologic details of individual s tudy patients. Main Outcome Measurements: Presence and coexistence of rectal mucosal dysplasia (high or low grade), mucosa classified as ind efinite for dysplasia, and acute UC (crypt abscess or cryptitis) in th e ATZ. Results: Of 94 ATZ tissue specimens, acute intracryptic inflamm ation was present in 60 rectal mucosa specimens (64%). In 29 (48%) of these 60 specimens, inflammation was neither widespread nor intense. R ectal mucosal dysplasia (low grade but not high grade) was present in 15 (16%) of 94 ATZs specimens. Inflammation elsewhere in the rectal mu cosa accompanied dysplasia in 11 (73%) of 15 ATZ specimens. Rectal muc osa classified as indefinite for dysplasia was present in 24 (26%) of 94 ATZ specimens and coexisted with inflammation in 15 (63%) of these 24. Thus, rectal mucosal atypia was present in 39 (41%) of 94 ATZ spec imens, and in 26 (67%) of these 39, abnormal rectal mucosa coexisted w ith acute inflammation. Conclusions: Rectal mucosa in the ATZ can exhi bit active UC and/or atypia. Long-term monitoring is advisable if the ATZ is preserved during restorative proctocolectomy.