Fissure-in-ano

An elliptical or oval-shaped tear in the anal canal, starting at the anal verge and extending proximally for a varying length towards the dentate line.

Epidemiology

• 58% female
• Most commonly 20-30yo, but any age
• Can occur in children and cause constipation

Aetiology

• Primary:
  • Hard stool
  • Explosive diarrhoea
  • Anoreceptive intercourse
  • Anal trauma
• Secondary:
  • Crohn disease
  • UC
  • HIV
  • TB
  • Syphilis
  • Leukaemia
  • HSV
  • Anal cancer

Pathophysiology

• Can be conceptualised as an ischaemic ulcer
• Primary fissures are caused by direct trauma, which results in internal anal sphincter spasm, further exacerbating constipation, and ultimately decreasing blood flow to the anal mucosa and relative ischaemia at the site of the tear
• While present, fissures cause increased anal canal pressure, which returns to normal after healing
• Be suspicious of painless ulcers, lateral fissures or multiples fissures - STI or IBD, in many cases

Natural history

Acute fissures

• • Those symptomatic for <8 weeks
  • Likely to consist of a tear or ulcer beginning at dentate line
  • Likely to respond to medical management
    • 50% will heal with stool softeners, fibre and symptomatic control only
    • Cameron's does not recommend GTN cream for this population

Chronic fissures

• • Those present for >8 weeks, including those that have failed medical management
  • The fissure will fibrose, a skin tag will appear distally, and/or a hypertrophied papilla at the proximal end
  • The internal sphincter muscle may be visible at base of fissure

Presentation

• Intense anal pain during defecation, with sensation of tearing, persisting dull ache for 3-4/24 afterwards
• Can also have pain with movement/walking or sitting
• Small outlet bleeding is not uncommon
• Perianal swelling/lump (skin tag)
• Mucus discharge
• Chronic fissures: enlarge, get oedema, get a skin tag, can be associated with low inter-sphincteric fistula
• Need to differentiate from a chronic intersphincteric abscess, which you will feel as a pea-sized lump

Examination

• Generally quite evident visually, even with gentle separation of buttocks from outside
• Small, shallow anal ulcer with sentinel pile and oedema
• Puckering of anal skin due to intense spasm
• Digital exam often impossible - no need for it if severe pain, because you should be able to see it
  • Often possible in chronic fissure, along with proctoscopy
  • If you really want to examine, you can inject 2mL of lignocaine just under the fissure, and usually permits DRE
• 95% of all fissures are in the midline
• Usually posterior midline in men (>80% of all fissures for men)
• Anterior midline is proportionally more common in women (up to 20% of all fissures in women)
  • These anterior fissures are commonly associated with an external sphincter defect
  • Anterior fissures in young women could be secondary to obstetric trauma - the 'low-pressure' fissure, which is treated slightly differently

Treatment

Non-specific: (give to all patients)

• • If chronic constipation: fibre + Movicol, avoid straining, good anal hygiene
  • Local NSAID or LA preparations (esp. for acute) (can try haemorrhoid creams but may not help)
  • Steroids can help sometimes
  • Heat of any source is likely to help with spasm of anal muscle and therefore pain e.g. hot water bottle
  • Sitz baths

First-line: (add as initial step for all chronic fissures and many acute fissures)

• • Six weeks of GTN cream - apply over fissure after defecation and at night, up to four times a day if needed. Warn re: headache (30% get it, but normally gets better over time).
    • In the best study so far, from 2012, GTN improved healing rates from 35% to 49%
    • Don't use with hypotension, anaemia, glaucoma, Viagra
  • Can also try nifedipine 0.5% + lignocaine 0.5% cream twice daily - needs to be compounded, so more expensive and takes longer.

Second-line: (once failed GTN)

• • Botox injection. Inject to inter-sphincteric plane, away from the fissure, usually at 3 and 9 o'clock, although opinions vary - some say also anterior. Works in 50%, but recurrence rates at 1 year approach 50%. Can get transient incontinence, haematoma or sepsis, but unusual.
    • Cameron's suggests 20 units at 10 and 2 o'clock anteriorly in the inter-sphincteric groove. Sabiston's just says 20-100IU. UTD says it varies depending on preparation of botox used. I think 40 units on each side is a reasonable average.
    • Typically gives relaxation for three months
    • Can be done in office, or with a bit of sedation
    • Costs up to $600 for patients if they have to pay

Third-line:

• • Anal dilatation - old, now not used.
  • Internal sphincterotomy. Risk of incontinence 5%. Pre-op enema. Incontinence and soiling is usually transient up to 3/12, but 20% will get flatus incontinence. Complete long-term healing rates exceed 90%. Used only as last resort in women - exclude low-pressure fissure with clinical examination and manometry prior.
    • Lateral internal sphincterotomy is preferred method, can be performed either open or closed technique, fairly equivalent results, however most modern surgeons would stay well clear of the closed technique now.

Open

Parkes retractor to put fibres on stretch (if struggling to identify groove, try without muscle relaxant). Small, radially-oriented incision over the intersphincteric groove at 3 or 9 o'clock (not directly under the fissure - can lead to keyhole deformity and chronic leakage), dissecting out a plane both superficial and deep to the internal sphincter muscle, grasping it with Allis forceps, and cutting in the muscle with scissors or diathermy, for 5mm (previously up to length of the fissure, but this gives a higher risk of incontinence in long fissure; classically to the level of the pectinate line). Close the incision with absorbable suture in anoderm.

Closed

Index finger in the anal canal, insert an 11-blade scalpel in the intersphincteric groove, and cutting the muscle towards the finger

• • Fissurectomy, with or without advancement flap
    • Especially when patients have a low baseline sphincter resting pressure

Special populations

• Low-pressure fissures could be treated with anoplasty rather than sphincterotomy
• Fissures off midline should prompt an aetiologic workup
• Recurrent anal fissure
  • Consider why the LIS failed - was it incomplete?
  • Repeat LIS is often effective
  • Consider manometry - if hypotonic sphincter, may need anoplasty