Patterns of fecal incontinence after anal surgery

Conservative anal surgery, with maximum preservation of the anal sphincters and continence, is becoming increasingly possible with the emergence of new sphincter-sparing treatments. Many surgeons remain skeptical, however, of the nature and impact of incontinence after anal surgery. We aimed to characterize the patterns of anal sphincter injury in patients with fecal incontinence after anal surgery.

We reviewed our fecal incontinence database and studied a subset developing incontinence after anal surgery. Maximum resting and squeeze pressures and the distal high-pressure zone to mid-anal canal resting pressure gradient were evaluated. Anal ultrasounds were evaluated and specific postoperative lesions were characterized.

Patterns of sphincter injury in 93 patients with fecal incontinence after manual dilation, internal sphincterotomy, fistulotomy, and hemorrhoidectomy were studied. The internal sphincter was almost universally injured, in a pattern specific to the underlying procedure. One-third of patients had a related surgical external sphincter injury. Two-thirds of women had an unrelated obstetric external sphincter injury. The distal resting pressure was typically reduced, with reversal of the normal resting pressure gradient of the anal canal in 89 percent of patients. Maximum squeeze pressure was normal in 52 percent.

Incontinence after anal surgery is characterized by the virtually universal presence of an internal sphincter injury, which is distal in the high-pressure zone, resulting in a reversal of the normal resting pressure gradient in the anal canal. These data support concerns that non-sphincter-sparing anal surgery leads to fecal incontinence and is increasingly difficult to justify given the availability of modern sphincter-sparing approaches.