Clinical Evaluation, Etiology, and Classification of Anal Incontinence

The potential causes of AI, as reported by the literature [7], are examined below.

2.1 Anal Incontinence after Operations for Anal Fissure

A correlation observed between internal sphincterotomy and AI [8] was the stimulus for treatment with “chemical” sphincterotomy, i.e., nitrates, botulin toxin etc. Indeed, postsphincterotomy AI is likely to be temporary. However, AI is more frequent when the surgeon carries out a posterior sphincterotomy, because of the weak (without muscles) area behind the divided internal sphincter. Therefore the correct procedure is a lateral internal sphincterotomy, where the surgical defect is “protected” by the adjacent external sphincter.

2.2 Anal Incontinence after Operations for Anal Fistula

When patients affected by anal fistula are afraid of being incontinent after the operation, ask them about bowel function and parity. In cases of diarrhea or vaginal multiparity, choose an operation which does not damage the sphincters, e.g., a fistulectomy and advanced rectal or cutaneous flap rather than fistulotomy; or alternatively, opt for an innovation, such as a fistula plug or Permacol, which leave the sphincter intact (bearing in mind that the innovations like plugs or Permacol have a high rate of recurrence, up to 50%).

Reports show a low risk of AI in patients whose high fistulae were treated with a lay-open technique [9]. The simple lay-open procedure may have a success rate of 95% [10], but it is a fact that, in my experience at least, patients seem more concerned about losing their continence than having a fistula recurrence. That is why, in the past 20 years, the most frequently performed type of surgery for fistula changed from the lay-open to anal sphincter-preserving procedures.

2.3 Anal Incontinence after Operations for Hemorrhoids

AI may follow a hemorrhoidectomy performed in a patient who has already undergone a procedure for prolapse and hemorrhoids (PPH) [11].

2.4 Anal Incontinence after Operations for Anal Tumors

In local excision of an anal tumor, the surgeon has to excise tissues at a distance of 2 cm from the lower edge of the neoplasm in order to either avoid or minimize the risk of recurrence. Therefore some fibers of both the internal and the low external sphincter have to be removed. In this case, the surgeon may perform a sphincteroplasty at the end of the operation.

2.5 Anal Incontinence after Operations for Rectal Cancer

The risk of the so-called anterior resection syndrome is high (up to 90% in some series) [12] especially if the neoplasm is in the lower rectum. Oncologic radicality may impact on the structures involved in anal continence. The first structure to be impacted is the rectal reservoir, which has to be either totally or partially excised with the tumor. This, especially in cases of very low anterior resection of the rectum and coloanal anastomosis (with the suture just above the anus) or in cases of low intersphincteric resection, with the excision comprising the whole internal sphincter. The anterior resection syndrome also consists in anal pain or discomfort, diarrhea, lack of the “adaptation reflex” which is active if the rectum is present. Therefore, urgency and frequency may occur. Moreover, radiotherapy may worsen AI because the muscular tissue will become rigid, sclerotic, less elastic and will not function properly. In these cases, a Miles procedure and creating a colostomy may appear desirable. A sigmoidostomy evacuates formed stools and may be irrigated every other day, so that the patient might even avoid wearing the bag (except when going out) and wear just a smooth and flat cap to cover the stoma.

2.6 Anal Incontinence Following Operations for Slow-Transit Constipation

Colectomy and ileorectal anastomosis still have a place in the surgical management of slow transit constipation refractory to any conservative treatment (laxatives, enemas, etc.). According to some authors [13], it often worsens patients’ quality of life. I have carried out around ten of these operations myself.

2.7 Anal Incontinence Following Operations for Anorectal Stricture

The most frequent cause of anorectal stricture is the Milligan-Morgan hemorrhoidectomy, when the surgeon does not leave enough mucocutaneous bridges after removing the piles. Sometimes an anoplasty operation is needed, but good results may be achieved just by periodical irrigation through the anorectum [14].

2.8 Anal Incontinence Following Surgery for Inflammatory Bowel Diseases

Proctocolectomy and ileoanal anastomosis with an ileal reservoir has become the operation of choice, i.e. the “gold standard” in cases of total ulcerative colitis and familial adenomatous polyposis. When the diseased rectum has to be excised, a reservoir function for anal continence may still be maintained by constructing an ileal reservoir just above the ileoanal anastomosis. Nevertheless either minor soiling or AI may occur in around 20% of these patients, especially at night, when the function of the anal sphincters is reduced. Biofeedback is the therapy of choice in these cases, or surgically constructing a four-loop or “W” large-capacity reservoir above the anal canal. Performing the ileoanal anastomosis above the anorectal ring by stapling, and thus leaving intact the tissues responsible for discriminating low intestine content, can be an option as well, but it may leave a site of disease persistence, become dysplasia or, worse, cancer.

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