Anal Fissure


INTRO
Syn: fissure-in-ano.
Painful tear in the skin or anoderm overyling the distal sphincters.

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INCIDENCE
Common.
Females > males
Most at middle age.

Risk factors

Constipation.
Comorbidities:
Often goes together with haemorrhoids.
May occur in females after a pregnancy (anteriorly).

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AETIOLOGY

Trauma

Usually occur whilst passing a hard stool.
- this is not always the case, and may follow diarrhoea or normal stool passage.
Hypertonia of the internal anal sphincter is common in these pts
- relationship between this and fissures is unclear
Partly related to Western diet.

Infection
Occasionally seen in some STDs.

Inflammation

Crohn's.

Iatrogenic

Removing too much skin during a haemorrhoid op may mean anal stenosis and tearing of this when a hard motion is passed.

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BIOLOGICAL BEHAVIOUR

Pathogenesis

1. Anal fissures are elongated tears in the long axis of the mucocutaneous lining of the anal canal (anoderm), often extending from the dentate line to the anal margin.
Usually (>90%) in the posterior midline.
The posterior rectal wall curves forward from hollow of sacrum
- then turns sharply backwards at the anal canal.
- during defecation the pressure of the stool is mainly against posterior anal tissue.
- when a scybalous mass is being expelled, the overlying skin is stretched.
- and thus may tear.
- eliptical anatomy of the canal also means less support given in antero-posterior axis.

2. Experimental evidence suggests relative deficiency of posterior anal blood flow may contribute to persistence of the fissure.
- ie is a watershed area.
Although hard stools commonly implicated, explosive liquid stool can cause same result.
Occur anteriorly in 10% of female fissures cf 1% male fissures

3. 90%+ pts have high mean anal resting pressure.
-  spasm; implicated in poor healing.
- hence sphincterotomy, widens the anal canal.

Acute vs chronic.

Acute
<6 weeks
Accompanying spasm of the anal sphincter muscle.
Many of these heal spontaneously.

Chronicity
A self perpetuating cycle is established:
It is painful to defecate
- the patient is reluctant to do so
- the stools become firmer
- the fissure worsens
Pain is attributed to internal sphincter spasm.
Over time, distal skin may become oedematous and enlarged / form a skin tag / sentinel pile.
- the cephalad anal papilla may also enlarge.
- these changes attributed to chronic low-grade infection.
Pts who develop chronic fissures may be susceptible.
- abnormal spasm after dilation of the sphincter, abnormal baseline pressure .

Post-partum
In women post-partum the damaged pelvic floor and attenuated perineal body means a lack of support of the anal mucous membrane.
Hence anterior anal fissures may occur.
Recent Doppler studies suggest that a perpetuating post-traumatic low blood supply and relative ischaemia may contribute to these.

Complications
Infection / abscess
Invasive infection may accompany chronic disease.
Intersphincteric abscess formation possible, with perianal abscess or rupture into anal canal.
Multiple fissures
May complicate skin disease, scratching, IBD, anal receptive intercourse

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MANIFESTATIONS

Symptoms
Local
Pain
The dominant symptom.
- squamous epithelium is highly sensitive.
Sharp and severe; often described as 'tearing'.
Starts during defecation.
- as the ulcer is stretched.
Lasts for minutes to hours.
Then ceases suddenly.
Intermittent remissions of days or weeks.
The patient thus avoids defecating, becoming constipated following this regimen: "a large dose of senna on Saturday night, then retire to the toilet on Sunday morning with a bottle of whisky and the newspaper" (B&L).

Bleeding

Usual.
Passage of bright red blood following the stool / streaks on the paper.
Usually slight.

Change in bowel habit
Occasionally pts have diarrhoea / alternating bowel habit.

Other
Pruritis, swelling, perhaps prolapse associated.
Slight mucus discharge in chronic cases.

Signs
Observe
Put in left lateral position, bum over edge of table.
Gently part the buttocks to reveal the fissure.
The pt often has a 'shy anus'
- ie you get a fleeting glimpse of the fissure before sphincter contraction withdraws it from view.
Fissures are usually located in the midline posteriorly (90%).
- or sometimes anteriorly (10%) in females, particularly after pregnancy.
- if located away from here, consider (eg) crohns, STD, hidradenitis, as is atypical.

Acute
Extends through skin of anal margin into anal canal.
A little inflammatory induration or oedema at edges.

Chronic
Inflamed and indurated margins.
The base consists of either scar or the lower border of the internal sphincter.
- sphincter has a characteristic whitish fibre appearance.
The ulcer is canoe-shaped.
A sentinel ('guarding') skin tag is often seen at the anal margin.
- this develops from heaped up granulated oedematous tissue.
- a hypertrophied anal papilla may be visible at the upper end of the anal canal.
The spasmodic internal sphincter may be organically contracted due to infiltration of fibrous tissue.

Palpate
Feels like a buttonhole.
PR is unnecessary - extremely painful and associated with anal spasm.
If you must perform PR then apply 5% xylocaine to cotton wool and leave in place for 5 minutes.
- better to leave it until later

Differential
STDs
Fissure of Crohn's disease
Usually deep with indolent edges, may be multiple and at atypical sites, and are usually less painful.
Anal SCCs
(In early stages)
Excise if any doubt.

An atypical appearance should question the diagnosis.
- lateral location, extension to the verge / above the dentate, extension through the sphincter = atypical.


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INVESTIGATIONS

The diagnosis is best established by examination under GA.
It is advisable to send any chronic tissue taken out for histopathology.

Endoscopy
Recommended; can be delayed 4-6 weeks until pain resolved with medical management.

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MANAGEMENT

Aim is to completely relax the internal sphincter.
This relieves pain.
And allows slow healing.

Conservative
Usually conducted first due to complications of sphincterotomy.
Often only a temporary solution.
Best for patients presenting acutely (within 3-6 weeks of symptom onset).

Four week regimen:

1. Warm sitz baths b.d. - e.g. once after defecation, once before bed
-  decrease anal canal pressures. e.
2. Stool softeners (fibre agents best)
--> Rates of healing are high for new fissures; less if chronic
- also advise on dietary fibre, adequate hydration; avoiding constipation

Chemical Sphincterotomy
Appropriate (in addition to above).
Cochrane Review 2009 : good evidence for chance of cure with conservative therapies as follows:
(All have similar efficacy)
3. Glyceryl trinitrate bd-tds (0.2% cream)
- releases NO, relaxant and vasodilation.
- patient should lie down when applying the ointment as side effects are significant eg headache.
- use a glove, pea sized piece on fingers to limit side effects.
- 50% heal but 50% of those relapse; sentinel pile (chronic fissure) helps predict failure.
- starts working in a few days, but typically 4-6 weeks, so wait that long for review. 
- continue for another 4-6 weeks if working.
4. Topical diltiazem (1-2% tds for 4 weeks) has similar efficacy and fewer side effects.
- requires a compounding pharmacy.

5. Botox is not widely used despite good logic behind it.
- 100u diluted in 2mL of normal saline; 20-40u injected into IAS base at either side of fissure
- 50% healing, but again high recurrence.
- needs further work to define how to use optimally.

Warn some risk of partial incontinence during therapy.
Nothing else shown better than placebo including topical steroids or lignocaine

Operative
For patients failing medical therapy
Operative management remains in no danger of becoming outdated at present.

EUA and colonoscopy
Rule out associated problems

Lord's procedure
Anal stretch is dangerous and no longer practiced

Tailored lateral internal sphincterotomy.

98% healing; 1% incontinence
Do not perform in IBD

See procedure

Advancement flap
- if all else fails, can consider
- higher risk of incontinence and more complex
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References
Metcalf, AM.  Surg Clin N Am 82 (2002) 1291-7.
Sabistons 17th
Cameron 10th