Increased anal resting pressure and rectal sensitivity in Crohn's disease

Anal pathology occurs in 20 to 80 percent of patients with Crohn's disease in which abscesses, fistulas, and fissures account for considerable morbidity. The etiology is not clearly defined, but altered anorectal pressures may play a role. This study was designed to investigate anorectal physiologic conditions in patients with Crohn's disease compared with healthy controls.

Twenty patients with Crohn's disease located in the ileum (n = 9) or the colon (n = 11) without macroscopic proctitis or perianal disease were included. All were subjected to rectal examination, anorectal manometry, manovolumetry, and rectoscopy. Comparison was made with a reference group of 173 healthy controls of whom 128 underwent anorectal manometry, 29 manovolumetry, and 16 both examinations.

Maximum resting pressure and resting pressure area were higher in patients than in controls (P = 0.017 and P = 0.011, respectively), whereas maximum squeeze pressure and squeeze pressure area were similar. Rectal sensitivity was increased in patients expressed as lower values both for volume and pressure for urge (P = 0.013 and P = 0.014, respectively) as well as maximum tolerable pressure (P = 0.025).

This study demonstrates how patients with Crohn's disease without macroscopic proctitis have increased anal pressures in conjunction with increased rectal sensitivity. This may contribute to later development of anal pathology, because increased intra-anal pressures may compromise anal circulation, causing fissures, and also discharging of fecal matter into the perirectal tracts, which may have a role in infection and fistula development.