ANAL WALL THICKNESS UNDER NORMAL AND INFLAMMATORY CONDITIONS OF THE ANORECTUM AS DETERMINED BY ENDOLUMINAL ULTRASONOGRAPHY

Objectives: To determine the normal dimensions of the anal wall and if there mere detectable differences in inflammatory disorders. Methods: A cross-sectional survey was performed on all patients referred to a university anorectal ultrasound clinic who had either perianal Crohn's disease (17 patients), ileoanal pouches (15 patients), perianal fistu la (15 patients), or previous radiation to the rectum (5 patients). Re sults were compared to 40 normal controls. Anal wall thickness (AWT), mucosa, submucosa, internal sphincter thickness (MSIT), and external s phincter thickness (EST) were measured or calculated. Intra- and inter observer reliability was assessed. Results: The mean AWT was 14.8 mm ( 95% CI: 14.0-15.6), mean EST was 8.3 mm (95% CI: 7.6-9.0), and the mea n MSIT was 6.5 mm (95% CI: 5.8-7.2) in the control subjects. Measureme nts did not differ significantly with sex or with an increase in age. Patients with perianal Crohn's disease, ileoanal pouches with septic c omplications, and previous local radiotherapy had significant increase s in anal wall thickness. In Crohn's disease, the significant increase was in MSIT, whereas, in the pouch patients, the increase was in the EST. Reliability studies demonstrated a learning curve with experience and a better correlation with determination of AWT than MSIT. Conclus ions: Patients with anorectal inflammatory conditions have increased t hickness in anal wall dimensions.