Anal Fissure

An anal fissure is a break or tear in the skin of the anal canal, often noticed by bright red anal bleeding on toilet paper, undergarments, or in the toilet. Acute anal fissures are typically painful after defecation, whereas chronic fissures may show reduced pain intensity and become cyclical.

Signs & Symptoms

An anal fissure is a break or tear in the skin of the anal canal, often noticed by bright red anal bleeding on toilet paper, undergarments, or in the toilet. Acute anal fissures are typically painful after defecation, whereas chronic fissures may show reduced pain intensity and become cyclical.

Causes

Most anal fissures result from stretching of the anal mucous membrane beyond its capability. Superficial fissures resemble paper cuts and may self-heal within weeks. Chronic and deeper fissures often persist due to spasms of the internal anal sphincter muscle, which impair blood supply and can lead to non-healing ulcers that may become infected.

Common causes include:

• Constipation
• Passing large, hard stools
• Prolonged diarrhoea
• Childbirth trauma in women
• Anal sex
• Crohn's disease
• Ulcerative colitis
• Poor toileting in young children

In older adults, decreased blood flow to the area can be a factor. Lateral fissures may indicate conditions such as tuberculosis, occult abscesses, leukaemic infiltrates, carcinoma, AIDS, or inflammatory bowel disease. Sexually transmitted infections such as syphilis, herpes, chlamydia, and human papillomavirus can also contribute.

Diagnosis

External anal fissures can be diagnosed through visual inspection. Internal fissures can be diagnosed using a beak proctoscope, Chelsea Eaton anal speculum, Park anal retractor, or by digital rectal examination.

Narrow fissures might not be detected by finger palpation due to reduced tactile sensitivity from gloves. Colonoscopy, sigmoidoscopy, or normal proctoscopy are not suitable for diagnosing anal fissures but are used for internal haemorrhoids and other rectal diseases.

Prevention

To prevent anal fissures, adults should avoid straining during defecation by treating and preventing constipation through a high-fibre diet, adequate water intake, occasional stool softeners, and avoiding constipating agents.

Prompt treatment of diarrhoea and careful anal hygiene, including using soft toilet paper and cleaning with water or sanitary wipes, can also help. Lubricating ointments may be used to prevent irritation, although haemorrhoid ointments should be avoided as they constrict blood vessels.

In infants, frequent diaper changes and ensuring adequate fluid intake can prevent fissures. Addressing underlying causes is usually sufficient for healing.

Treatment

Non-surgical treatments are recommended initially for both acute and chronic anal fissures. These include topical nitroglycerin or calcium channel blockers like diltiazem, as well as botulinum toxin injections into the anal sphincter. Other measures include warm sitz baths, topical anaesthetics, high-fibre diets, and stool softeners.

Medication

Local applications of nitroglycerine ointment, nifedipine ointment, or diltiazem aim to relax the sphincter muscle and promote healing. While effective, nitroglycerine ointment may cause headaches due to systemic absorption. Botulinum toxin injections can also be used, but may require additional treatments over time. Combination therapies offer high cure rates.

Surgery

Surgery is reserved for cases where medical therapy has failed after one to three months. The primary concern is the risk of anal incontinence, which can range from minor gas control issues to loss of solid stool. Lateral internal sphincterotomy (LIS) is the preferred procedure due to its simplicity and high success rate (~95%).

It involves partially dividing the internal anal sphincter to reduce spasming and improve blood supply, facilitating healing and reducing recurrence. However, long-term continence disturbances can occur in about 14% of patients, necessitating careful patient selection.

Anal Dilation

Anal dilation, or stretching, has fallen out of favour due to high rates of incontinence. Controlled studies have shown mixed results, with some indicating effectiveness and low side effects when performed correctly.

Fissurectomy

Fissurectomy involves excising the skin around the fissure, promoting new tissue growth and healing.

Epidemiology

Anal fissures occur in approximately 1 in 350 adults, affecting men and women equally, most commonly between ages 15 and 40.

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Self-assessment MCQs (single best answer)

What is a common sign of an anal fissure?

Which of the following is NOT a common cause of anal fissures?

Which diagnostic tool is NOT suitable for diagnosing internal anal fissures?

Which preventive measure is recommended for adults to avoid anal fissures?

What is the main goal of using nitroglycerin ointment in treating anal fissures?

Which of the following is a surgical option for treating anal fissures?

What is a potential long-term complication of lateral internal sphincterotomy?

Which condition might be indicated by the presence of lateral anal fissures?

Why has anal dilation fallen out of favour as a treatment for anal fissures?

What is the primary benefit of fissurectomy as a treatment for anal fissures?