Abnormal rectal mucosa of the anal transitional zone in ulcerative colitis

Abstract

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 proctocolectomy specimens for determination by surgical pathologists of specific histopathologic features in rectal mucosa of the ATZ.

Setting: Surgical referral center for restorative proctocolectomy.

Patients: Ninety-four patients with symptomatic UC underwent restorative proctocolectomy between January 1991 and December 1994.

Interventions: Specific histopathologic features of active UC in the ATZ were evaluated by a single reviewer who did not know the clinicopathologic details of individual study patients.

Main outcome measurements: Presence and coexistence of rectal mucosal dysplasia (high or low grade), mucosa classified as indefinite for dysplasia, and acute UC (crypt abscess or cryptitis) in the ATZ.

Results: Of 94 ATZ tissue specimens, acute intracryptic inflammation was present in 60 rectal mucosa specimens (64%). In 29 (48%) of these 60 specimens, inflammation was neither widespread nor intense. Rectal mucosal dysplasia (low grade but not high grade) was present in 15 (16%) of 94 ATZs specimens. Inflammation elsewhere in the rectal mucosa accompanied dysplasia in 11 (73%) of 15 ATZ specimens. Rectal mucosa 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 specimens, and in 26 (67%) of these 39, abnormal rectal mucosa coexisted with acute inflammation.

Conclusions: Rectal mucosa in the ATZ can exhibit active UC and/or atypia. Long-term monitoring is advisable if the ATZ is preserved during restorative proctocolectomy.