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An anal fissure is a painful tear in the mucous membrane of the anal canal.

An anal fissure is a radial lesion in the mucous membrane of the anal canal (anoderm). In 80-90% of cases, the tear is localized in the posterior commissure of the anal canal (distal to the dentate line) in the so-called "6 o'clock incision position". A distinction is made between primary and secondary as well as acute and chronic anal fissures. Typical symptoms are pain during defecation and burning after a bowel movement. Anal fissures are diagnosed by inspection and palpation as well as proctoscopy. Therapeutically, the aim is to reduce the sphincter hypertonicity - initially conservatively, and surgically if this is not effective enough.

Epidemiology

Anal fissures are relatively common. However, there are no precise epidemiological data on incidence and prevalence. The lifetime risk - i.e. the probability of suffering an anal mucosal tear in the course of a lifetime - is 8 to 11 percent. There is no significant gender preference.

Causes

Primary anal fissures: Primary anal fissures occur spontaneously and without an underlying disease. Factors that increase sphincter tone are discussed as possible causes. These primarily include constipation and hard stools. Risk factors include a low-fibre diet, obesity and hypothyroidism. Pregnancy: The increased incidence during pregnancy may be due to constipation. Diarrhea: A study from 2006 also showed an increased incidence of anal fissures in patients with diarrhea.

Secondary anal fissures: Secondary anal fissures usually appear as uni- or multifocal ulcerations in the anal canal or on the anal verge. They can be mechanical, bacterial, viral, inflammatory or immunological, as well as drug-induced and toxic. The pathogen-related venereal diseases include infections with the human immunodeficiency virus (HIV), cytomegalovirus (CMV), herpes simplex viruses (HSV) and Chlamydia trachomatis (serotypes S-K, L1-L3) as well as tuberculosis, syphilis, gonorrhea, histoplasmosis and leishmaniasis. Crohn's disease can also be associated with perianal pathology. An association with anal fissures is significantly higher in this group than in the population as a whole.

Pathogenesis

The exact mechanism of anal fissure development is still unclear. Increased tone of the internal sphincter muscle and non-drained low-grade infections are discussed as significant pathogenetic factors. However, the success of most treatment concepts that reduce sphincter tone tends to speak in favor of hypertonicity. The increased sphincter pressure is assessed by the current guideline as a central point in the vicious circle of hypertonus, ischemia, inflammatory stimulus and pain.

Symptoms

An anal fissure usually causes severe, sometimes tearing pain during defecation. Afterwards, many sufferers experience a sharp burning sensation. Depending on the type of anal fissure (acute or chronic), the discomfort can last for several hours after defecation. In addition to the anal pain, patients often notice blood deposits on the stool or traces of bright red blood on the toilet paper. The symptoms can significantly reduce the patient's quality of life.

Acute and chronic anal fissures

Depending on the time of occurrence, a distinction is made between acute and chronic anal fissures. The latter is considered to be acute if the symptoms persist for longer than six to eight weeks.

Diagnosis

An anal fissure is suspected on the basis of the patient's medical history. The proctological examination includes inspection and palpation and - if possible - a proctoscopy. an anal fissure can usually be visualized by spreading the nates. In 80-90 percent of cases, the fissure is located in the posterior commissure of the anal canal (distal to the dentate line) in the so-called "6 o'clock lithotomy position". A proctoscopy serves to confirm the suspected diagnosis and exclude possible differential diagnoses. However, due to the pain and increased sphincter tone, it is not initially feasible in a large number of patients. In the case of an atypically localized anal fissure (acute or chronic), an extended diagnosis is indicated. This should include serological and microbiological tests for HIV, CMV, Chlamydia trachomatis, lymphogranuloma venereum, Neisseria gonorrhoeae, histoplasmosis and leishmaniasis. If Crohn's disease is suspected, a colonoscopy with biopsy should be performed in accordance with the guideline.

Differential diagnosis

An anal fissure can present similarly to other diseases. These should be excluded in the differential diagnosis. These include above all

  • cryptogenic perianal abscesses and anal fistulas
  • Skin diseases
  • Precancerous diseases
  • Lymphomas
  • deep-seated rectal carcinomas
  • Anal carcinomas

Therapy

Therapy: acute anal fissure

Treatment depends on the duration and form of the anal fissure.

Acute anal fissures heal on their own in many cases. The following conservative therapies are used for therapeutic intervention:

  • Diet: high-fiber and fiber-rich diet
  • Nutritional supplements (for example with psyllium husks); a change in diet is also recommended to prevent recurrence
  • Sitz baths (e.g. with bran): no influence on the healing rate, but can increase patient comfort; occasional skin irritation possible
  • local application of calcium antagonists: for example nifedipine for three to eight weeks
  • Local anesthetics: Symptom relief possible, no influence on healing rate; occasional skin irritation and infections possible
  • local application of steroids: should be reserved for patients with secondary conditions, such as local eczema

Therapy: chronic anal fissure

Compared to acute fissures, chronic anal fissures are much less likely to heal with conservative treatment. Nevertheless, all patients should be offered a six-week trial of conservative treatment before surgical treatment is initiated.

Conservative treatment

The current guideline recommends the following conservative treatment measures for chronic anal fissures:

  • Calcium channel antagonists (CCA): calcium channel blockers such as nifedipine lower the sphincter tone by reducing the influx of calcium ions into the smooth muscle cells. As a result, their contractility is reduced and the strained anal mucosa relaxes. Locally applied or topical CCA should be used as first-line drug therapy. Oral CCA can also be used for therapy. However, topical application is preferable due to the better ratio of effect to side effect.
  • Nitrates: Nitrates such as gylcerol trinitrate (GTN) relax the smooth muscle cells via the release of nitric oxide and thus reduce the anal resting pressure. They have a similar effect to calcium antagonists and can be used as topical agents for the treatment of chronic anal fissures. The occurrence of frequent side effects, particularly headaches (in around 30 percent of cases), has been shown to limit treatment.
  • Botulinum toxin A: As a neurotoxic protein, botulinum toxin A inhibits the transmission of excitation from the nerve cell to the muscle cell and thus acts as a muscle relaxant. After local injection, the resting tone of the sphincter ani internus muscle is reduced in the case of an anal fissure. In comparison to GTN and CCA, meta-analyses show slightly - but significantly - higher healing rates for botulinum toxin A. In cases of resistance to calcium antagonists, the use of the neurotoxin as a second-line therapy (as an alternative to surgery) can be discussed with the patient. In the case of a hypertonic sphincter, a dosage of 20 to 40 U Botox® equivalent is applied intrasphincally for the first intervention.

Surgical procedures

The following surgical procedures are recommended for the treatment of chronic anal fissure:

  • Fissurectomy

Fissurectomy has a higher healing rate than all conservative measures - but a lower rate than lateral internal sphincterotomy (LIS). The latter carries a higher risk of incontinence. The guideline experts have therefore opted for fissurectomy as the first-line treatment for surgical procedures.

  • Advancement flap: An anal advancement flap can be performed in different variations. For example, the anal mucosa is mobilized via the fissurectomy wound or the perianal skin is moved externally via the fissure (V-Y flap, "house" flap, dermal flap). According to the guideline, an advancement flap can be performed in addition to a conventional fissurectomy as a first-line surgical treatment or as a second-line treatment after an unsuccessful fissurectomy.
  • Lateral internal sphincterotomy (LIS): Lateral internal sphincterotomy or lateral internal sphincterotomy (LIS) is a surgical treatment procedure to separate the sphincter muscles. Open LIS is performed by incision through the intersphincteric groove, separation of the internal sphincter muscle from the anal mucosa by blunt dissection and division of the internal sphincter muscle under visual control; closed LIS is performed by stab incision in the intersphincteric space and blind division of the internal sphincter muscle under digital control.

Both techniques achieve similar results in terms of healing success and side effects. According to the current US guideline, LIS is considered the gold standard among surgical procedures due to its high cure rates.

Prognosis

An acute anal fissure usually heals spontaneously after a few weeks and without consequential damage. Chronic anal fissures also have a good prognosis after conservative treatment or surgical intervention. When choosing the surgical method, the increased risk of fecal incontinence should be considered.