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.

Patients report difficult painful defaecation, narrow stools, incomplete evacuation and prolonged straining.

Severe disease can produce faecal impaction or overflow leakage.

Examination demonstrates a scarred narrowed anal canal with reduced elasticity.

Diagnosis is clinical.

Examination under anaesthesia may be necessary when pain or severe narrowing prevents adequate assessment.

Exclude recurrent malignancy, Crohn disease and active fissure when clinically relevant.

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.

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.