Colorectal Surgery

Anal Fissure

An anal fissure is a painful anoderm tear, usually posterior midline; relieve constipation and sphincter spasm, and investigate atypical or refractory disease for secondary causes.

In a nutshell

Anal fissure causes severe post-defecation pain and bright-red bleeding. Confirm a typical midline tear gently, soften stool, relax the internal sphincter, and refer atypical or refractory disease to exclude secondary causes and consider sphincter-preserving treatment.

Classic presentation

Sharp pain during/after defecation with a small amount of bright-red blood and a posterior midline tear, sometimes with a sentinel tag.

Key points

Break the pain–spasm–ischaemia cycle: prevent hard stool, avoid straining and use topical sphincter-relaxing treatment when needed.
Do not force a painful DRE or proctoscopy; gentle inspection may be enough initially.
Lateral, multiple, painless, indurated or non-healing fissures are atypical and need investigation for Crohn disease, infection or malignancy.
Topical GTN or diltiazem is used for persistent disease; check BNF cautions and local protocol (see BNF/local protocol for medicines).
Refractory chronic disease may need botulinum toxin or surgery; weigh healing against continence risk.
Fever, constant worsening pain, swelling or pus suggests abscess rather than an uncomplicated fissure.
Safety-net bleeding, weight loss, bowel-habit change and a lesion that does not heal.

First-line investigation

History and gentle perianal inspection; defer painful instrumentation and investigate atypical findings.

Management

Confirm a typical fissure gently

Use focused history and inspection; avoid forced DRE or instrumentation when pain is severe.^1,3

Soften stool and reduce trauma

Fibre, fluid, stool-softening laxative, regular toileting and avoidance of straining are the foundation.^1,3

Relax the internal sphincter

Use topical GTN or diltiazem for persistent disease with BNF/local-protocol cautions (see BNF/local protocol for medicines).^1,4,5

Refer atypical or refractory disease

Investigate secondary causes and refer chronic non-healing disease for specialist options including botulinum toxin or sphincter-sparing surgery.^1,2

Check healing and safety-net

Review pain, bleeding, stool pattern and adverse effects; escalate fever, abscess features, heavy bleeding, weight loss or persistent atypical lesions.^1,3

Exam traps

A fissure is usually painful; painless bleeding or a mass needs another diagnosis.
Posterior midline is typical; lateral or multiple fissures suggest secondary disease.
Do not use repeated painful examination as proof of diagnosis.
Surgery is effective but can cause incontinence; risk-stratify before sphincterotomy.

Illustrations

The pain-spasm-ischaemia cycleFlow diagram showing a mucosal tear causing pain, pain triggering internal sphincter spasm, spasm compressing the blood supply, and resulting ischaemia preventing healing and perpetuating the tear.PassFinals · original

Posterior midline anal fissure with sentinel tagClinical photograph of a longitudinal anoderm tear at the posterior midline with an associated distal skin tag characteristic of a chronic fissure.Bernardo Gui, Wikimedia Commons · Public domain

Mechanism of action of topical GTN and diltiazemDiagram illustrating how topical smooth-muscle relaxants lower internal anal sphincter tone, restoring blood flow to the ischaemic fissure base.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.