A manometric study of anorectal function after surgery for anal fistula, with special reference to incontinence.

Anorectal function was manometrically studied in 199 adults on average 9 years after laying open of anal fistula, in order to determine the factors adversely affecting anal continence. Resting anal pressure, and especially squeeze and voluntary contraction pressures, were significantly reduced in the 67 patients with defective anal control. Maximal squeeze and contractile pressures were significantly lower in women than in men but, like maximal resting pressure, were uninfluenced by age. Fistula type significantly influenced maximal resting and squeeze pressures, with tendency to low pressures and high incidence of defective anal control after operation for high intermuscular fistula. Maximal contractile power was unrelated to extent of external sphincter division. Rectal sensation and activity of the rectoanal reflexes did not appreciably differ between the continent patients and the others. Digital assessment of sphincter tone at rest and at maximal contraction correlated well with the respective anal pressures, but was an unreliable indicator of anal continence. The manometric findings warrant maximal preservation of the anal sphincter musculature, but fistula healing must not be thereby endangered.