7.1.1 Anal Fissure

Anal fissure is the most frequent cause of acute anal pain in Europe. The incidence peak is in young adults. The reported annual incidence in Europe is 0.11 % (1.1 cases per 1,000 person-years), but due to unreported cases, the true incidence is probably much higher. The prevalence ranges widely by age and patient characteristics (e.g. significantly higher in females). Even after operative fissure treatments, there is a notable rate of recurrences (approximately 1-6 %).

The exact etiology of anal fissures is unknown, but usually the initiating factor is a trauma caused by hard or forceful defecation. Obesity, low fiber diets, hypothyroidism, anal tumors and chronic constipation have been associated with the development of anal fissures. Regarding pathogenesis, a genetic disposition is recognized. Additional possible abnormalities are spasms, hypertonicity and hypertrophy of the internal anal sphincter that lead to elevated anal canal and sphincter resting pressures. Anal fissures can also occur after trauma during delivery and as a complication of anal surgery. Anal fissures may infrequently be associated with Crohn’s disease, HIV infection and tuberculosis.

The typical symptom is acutely occurring lacerating pain during bowel movements, with the pain lasting even hours after defecation. The pain commonly recurs with every defecation, which may lead to a cycle of worsening constipation, harder stools, and increase of anal pain and discomfort (vicious cycle). Many patients note bright-red blood on the toilet paper or stool. Small amounts of blood may be visible in the toilet bowl, but unlike hemorrhoids, significant bleeding does not usually occur. Thus, anal fissures do not cause anemia. The symptoms of anal fissure are relatively specific, and the diagnosis can often be made on patient history alone.

Most frequently anal fissures resolve spontaneously. After a duration of 6-8 weeks the anal fissure is regarded as chronic. Anal fissures have a tendency to recur; the recurrence rate with non-surgical treatments is high, whereas that of surgical sphincterectomy is less than 6%.

A typical complication is a submucous abscess, which impedes wound healing. An abscess can lead to fistulas of the skin or mucosa surface. More rare complications include anal thrombosis, ulceration and incontinence. In immunocompromised patients, the fissure can serve as a port of infection.

The diagnosis is usually made clinically, based on the typical findings of inspection. Proctoscopic and rectal examination is painful and often not necessary. If the anal fissure is not visible, the tender wound base of the fissure may be recognizable by gentle digital examination.

If symptoms are typical and if the fissure is located in the posterior or anterior midline (idiopathic anal fissure), no further tests (biopsy and endoscopy) are necessary.

Occasionally, fissures are not easily visible and proctoscopy is required to locate them.

Endoscopy (e.g. to exclude Crohn disease) and biopsy (e.g. to exclude malignancy) are needed in the following constellations: fissure located in an untypical location (e.g. laterally), chronic fissures with protracted wound healing, failure to respond to appropriate therapy, or those who have recurrent anal fissures after surgical therapy.

If fissures are located off the midline, if there are multiple fissures or if an underlying illness is conceivable (notably Crohn disease, anal squamous cell cancer, or HIV infection), appropriate tests should be ordered. These may include the following: microbiologic swabs, systemic inflammatory parameters, fecal calprotectin, HIV testing, biopsy.

First-line medical therapy includes stool-bulking agents, such as fiber supplementation and stool softeners. Laxatives should be used as needed to maintain regular bowel movements and treat underlying constipation.

Second-line therapy consists of topical medicaments that decrease the muscle tonus of the inner anal sphincter. Nitroglycerin applied in different formulations directly to the internal anal sphincter (e.g. nitroglycerin 0,4% ointment or anal suppositories). Comparable to the use of nitroglycerin ointment, nifedipine ointment is also available in some European countries. The topical treatment should be continued even after the symptoms subside (e.g. 2 months).

In addition to topical treatments, botulinum toxin has been used to treat acute and chronic anal fissures, but poses a small risk of injection site infections. The effect lasts some months, until the regeneration of free nerve endings.

If the anal fissure in unresponsive to conservative treatment and lasts over 2 months surgical intervention should be evaluated. Symptomatic chronic fissures should be treated operatively because they only rarely heal spontaneously.

In chronic fissures, surgical revision with possible skin-subcutaneous flap reconstructions may lead to healing. Other surgical therapies consist of sphincter dilatation or operative sphincterectomy, which pose a small risk of postoperative incontinency (usually concerning gases).