Postpartum Anal Fissure

Postpartum anal fissure is a tear in the lining of the lower anal canal, usually in the posterior midline, causing sharp pain with passing stool and bright red blood. It affects 10 to 20 percent of women after birth, and results from straining at the second stage, hard stool, constipation and trauma. It matters because pain causes the woman to hold on to stool, which leads to more constipation and spasm of the internal sphincter and delays healing.

• Risk factors: constipation, long second stage, instrumental delivery, anal sphincter injury, previous fissure, iron tablets, dehydration, breastfeeding with low fluid intake.
• Acute fissures (under 6 weeks) heal in 60 to 90 percent with simple care.
• Chronic fissures last more than 6 to 8 weeks and show a sentinel skin tag and exposed muscle.

Women have severe burning or cutting pain with defaecation lasting minutes to hours, and bright red blood on the paper or stool. They may avoid going to the toilet.

• A visible tear when the buttocks are gently parted.
• Spasm of the anal sphincter that makes digital examination painful.
• Differential diagnosis: haemorrhoids, perianal abscess, perianal haematoma, third or fourth degree tear, anal herpes, Crohn disease, anal cancer, anal tuberculosis, syphilis or HIV related anal ulcer.
• Complications: chronic fissure, perianal abscess, fistula, constipation with overflow, sphincter spasm, avoidance of defaecation, pain.

The approach is inspection, without forceful digital examination.

• Gentle separation of the buttocks shows a linear tear, often in the posterior midline, with a sentinel skin tag in chronic cases.
• Digital rectal examination or anoscopy is deferred if too painful, and done under local anaesthetic if needed.
• A fissure off the midline, multiple fissures, or fissure with systemic symptoms needs tests for HIV, syphilis, Crohn disease and tuberculosis.
• Examination for sphincter injury after a tear.

The principle is to soften stool, relax the sphincter and relieve pain, with surgery reserved for chronic fissure that fails medical care.

• Supportive: fibre 25 to 30 g daily; fluids 2 to 3 litres; warm sitz baths for 10 to 15 minutes after each bowel movement and 2 to 3 times daily; avoid straining; hold a pad against the perineum when passing stool; breastfeeding continues.
• Pharmacological: lactulose 15 mL oral 12-hourly; ispaghula husk 3.5 g oral 12-hourly with water; glyceryl trinitrate 0.4 percent ointment, a pea sized amount (about 1 cm, 1.5 mg) applied to the anal margin 12-hourly for 6 to 8 weeks (headache is common; avoid in hypotension); or diltiazem 2 percent cream applied to the anal margin 12-hourly for 6 to 8 weeks; lignocaine 2 percent gel applied 5 minutes before defaecation; paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours).
• Procedures: botulinum toxin A 20 to 30 units injected into the internal sphincter for chronic fissure after 8 weeks of failed medical care; lateral internal sphincterotomy for chronic fissure failing both, after 6 months postpartum.
• Special groups: women with a sphincter tear or low anal pressures, or who plan more births, avoid sphincterotomy and are offered botulinum toxin or advancement flap because of the risk of incontinence.
• Red flags: fissure off the midline, non healing beyond 8 weeks, perianal swelling or abscess, fever, severe unrelenting pain, weight loss, leakage of stool.
• Follow-up: review at 2 weeks and 6 weeks; anorectal assessment if the fissure persists beyond 8 weeks; review before any later birth.