Anal Stenosis

Anal stenosis is pathological narrowing of the anal canal caused by replacement of normal pliable anoderm with scar tissue.

Most acquired cases follow excessive anodermal excision during haemorrhoid surgery. Other causes include inflammatory bowel disease, radiation, trauma and previous anorectal reconstruction.

Distinguish anatomical stenosis from functional narrowing caused predominantly by sphincter spasm.

Mild stenosis can initially be treated with:

Fibre
Adequate fluid intake
Stool softening
Carefully supervised gradual dilation when appropriate

Avoid forceful uncontrolled anal dilation because mucosal tearing and further fibrosis can worsen the stenosis.

Moderate or severe anatomical stenosis generally requires anoplasty to replace scarred tissue with healthy pliable anoderm or perianal skin.

Options include:

House flap
Diamond flap
V to Y or Y to V advancement techniques
Other advancement or rotational flaps according to defect orientation

House flap reconstruction provides a broad segment of healthy tissue and has produced favourable functional outcomes in comparative series. ([pmc.ncbi.nlm.nih.gov](https://pmc.ncbi.nlm.nih.gov/articles/PMC10086798/))

Internal sphincterotomy is useful only when significant functional sphincter hypertonicity contributes to the narrowing. It cannot correct a fixed circumferential loss of anoderm by itself.

Prevention is critical during haemorrhoidectomy: preserve generous mucocutaneous bridges between excised haemorrhoidal columns.

Chronic Anal Fissure

A chronic anal fissure persists beyond the normal acute healing period and develops structural changes including a sentinel skin tag, hypertrophied anal papilla and exposed internal sphincter fibres.

Persistent internal anal sphincter hypertonicity reduces anodermal perfusion and prevents healing.

Maintain soft formed stool using fibre and polyethylene glycol when needed.

First line pharmacological sphincter relaxation can use:

Diltiazem 2% topical cream applied to the anal verge twice daily for approximately 6 to 8 weeks.

An alternative is:

Glyceryl trinitrate 0.2% to 0.4% ointment applied twice daily for approximately 6 to 8 weeks. Diltiazem provides similar healing with fewer headaches than topical nitrates.

Botulinum toxin is useful after topical treatment failure or when avoiding sphincter division is important.

A commonly used total dose is:

Botulinum toxin 20 to 60 units injected into the internal anal sphincter, divided between one or more sites. There is no single superior injection protocol.

Lateral internal sphincterotomy provides the highest healing rate and is appropriate for chronic primary fissure that persists despite medical treatment or in selected patients where definitive surgery is preferred. Divide only enough internal sphincter to reach approximately the proximal extent of the fissure rather than automatically dividing to the dentate line. Tailored sphincterotomy reduces unnecessary sphincter injury.

Avoid or use major caution with sphincterotomy in patients with baseline faecal incontinence, previous obstetric sphincter injury, inflammatory bowel disease or previous sphincter dividing anorectal surgery.

In these patients, fissurectomy with an advancement flap or botulinum toxin can preserve sphincter function. Healing after lateral internal sphincterotomy is approximately 88% to 100%, but continence risk must be considered individually.

Anal Stenosis

Overview

Clinical Features

Diagnosis

Management

Overview

Clinical Features

Diagnosis

Management