An anal fissure is a linear tear in the lower aspect of the anal canal. When this tear does not heal it then becomes an ulcer resulting in pain and spasm of the muscles of the anal canal. This condition results from trauma to the anus with the most common cause being the passage of hard constipated stool. Other causes include diarrhea, anoreceptive intercourse, childbirth, haemorrhoidal surgery, and chemotherapy. Importantly, this condition does not result in the development of cancer of the anus.
The classical symptom experienced is a sharp pain on the passage of stool. It is typically described like passing “bits of glass”. This pain is a result of muscle spasm around the anus and tearing. Associated bright red bleeding afterwards that is seen on the toilet paper and in the toilet bowl is common. When a fissure has been present for more than six weeks it is common to develop skin tags at the site of the anal fissure. Skin tags are a result of swelling and inflammation of the surrounding skin. Typically, your doctor or specialist will be unable to examine you due to severe pain and spasm and treatment is started based on symptoms. On occasion, examination under anaesthetic is necessary to make the diagnosis.
The first line of treatment for anal fissure should be conservative measures aimed at maintaining a diet high in fiber (bran, vegetables, whole wheat breads, etc.) and water (approximately 2 litres per day) to keep the stool soft and well formed. In addition, warm baths and keeping the area clean can be helpful in relieving the pain. In order to help relax the anal muscles and alleviate the spasm topical application of ointments (containing 0.2% GTN or 2% Diltiazem) are prescribed for approximately six weeks. The most common side effect of these medications, which limits their use, is a severe headache.
Surgical treatment is usually only performed when all conservative measures have been exhausted, and, after investigations have been performed to confirm the diagnosis and rule out any other sinister pathology. These investigations include anorectal physiology (manometry, ultrasound scanning) to assess for spasm and hypertrophy of the anal canal muscle and endoscopic (camera) examination of at least the left side of the colon. The “gold standard” surgical treatment that is usually performed is a lateral sphincterotomy. This involves partially cutting the inner most anal canal muscle to weaken it and relieve spasm. Sphincterotomy is always reserved as a last resort and is contraindicated in women of childbearing age, as there is a slight chance of incontinence afterwards. Alternatively, Botox injection into the internal anal muscle provides temporary muscle relaxation and healing to occur. Its effect usually lasts three months and can be repeated. At the time of surgery, it may be necessary to excise the fissure and the associated skin tags to augment healing. Immediate symptom relief usually occurs after surgery.
Botox injection usually carries a success rate of 60-65% versus 90-95% with lateral sphincterotomy. Rarely, in patients who develop a non-healing chronic anal fissure despite medical and surgical treatments an advancement skin flap to cover the fissure defect after excision may be necessary.