EFFECT OF TOPICAL 5-AMINOSALICYLIC ACID (5-ASA) THERAPY ON RECTAL MUCOSAL BIOPSY MORPHOLOGY IN CHRONIC ULCERATIVE-COLITIS

Classic teaching emphasizes that chronic ulcerative colitis is charact erized morphologically by the presence of fixed architectural and cell ular mucosal changes that categorize the process as chronic. To examin e the effect of topical 5-aminosalicylic acid (5-ASA) enemas on the pr esence of six histological features of chronicity in established chron ic ulcerative colitis, 123 mucosal biopsies were taken prospectively a t 1-month intervals, all from the same anatomic location (10 cm), from 14 patients treated with either 5-ASA or placebo enemas. The biopsies were evaluated for the presence of mixed inflammation in the lamina p ropria, crypt architectural abnormalities, basally located lymphoid ag gregates, basal plasmacytosis, villiform surface epithelial configurat ion, and Paneth cell metaplasia. Overall, 29% of biopsies from 64% of patients were histologically normal (no chronic features, no active di sease). Compared with patients treated with placebo enemas, patients t reated with 5-ASA enemas showed a significantly higher percentage of n ormal biopsies (36% ASA group vs. 12% placebo group; p = 0.005) and a lower percentage occurrence of each individual histological feature of chronicity. In addition, patients treated with 5-ASA had a higher ave rage number of normal biopsies per patient (3.0) than those treated wi th placebo enemas (1.3). Therefore, histologically normal-appearing mu cosal biopsies do occur in established cases of chronic ulcerative col itis, and this finding is enhanced by treatment with 5-ASA enemas. Awa reness of these results should prevent the presence of normal rectal m ucosal biopsy findings in chronic ulcerative colitis patients from bei ng misinterpreted as either evidence against this diagnosis or as repr esenting focal skip areas characteristic of Crohn's disease.