Anal Fissure
NICE CKS Anal Fissure. Last revised: Apr 2021.
NICE BNF Treatment summaries. Anal fissure.
Background Information
Definition
An anal fissure is defined as a split / tear in the anal canal lining (stratified squamous epithelium)
Aetiology
Multifactorial → resulting in local trauma to the anoderm
- Chronic constipation (most commonly) or diarrhoea
- Other factors: Internal anal sphincter hypertonia, local ischemia
Secondary causes:
- Crohn’s disease – classic cause of a secondary anal fissure
- Colorectal cancer
- Dermatological conditions (e.g. psoriasis, pruritus ani)
- STIs (e.g. HIV, syphilis, herpes simplex)
- Tuberculosis
- Anal trauma (e.g. previous anal surgery, anal sex)
The internal anal sphincter is the primary muscle implicated in anal fissures (not the external anal sphincter).
Relevant anatomy:
- Internal anal sphincter: smooth muscle that surrounds the upper 2/3 of the anal canal. It is involuntary, innervated by the enteric nervous system.
- External anal sphincter: skeletal muscle that surrounds the lower 1/3 of the anal canal. It is voluntary, innervated by the pudendal nerve.
Clinical Features
Typical presentation:
- Severe anal pain that occurs with defaecation
- Rectal bleeding is possible (usually a small amount of bright red blood on the stool or toilet paper)
Examination findings:
- Acute vs chronic anal fissure
- Acute anal fissures: typically a single superficial tear with well-demarcated edges
- Chronic anal fissures
- Wider and deeper tears
- Muscle fibres (of the internal sphincter) may be visible in the base
- Edges are often swollen
- Hypertrophied anal papilla at the proximal margin
- Skin tag at the distal margin
- Primary vs secondary anal fissure
- Primary anal fissure: usually singular and located at the posterior midline
- Secondary anal fissure: can be multiple, usually with an irregular outline, and located at lateral / anterior positions
An anal fissure that is NOT located on the posterior midline should raise suspicion of a secondary anal fissure, requiring further investigations.
Other suggestive features of a secondary anal fissure:
- Multiple fissures at a time
- Irregular outline
Complications
- Failure to heal / progression to chronic anal fissure / recurrence
- Anorectal fistula
- Infection and/or abscess
- Faecal impaction
Guidelines
Investigation and Diagnosis
Primary anal fissure is a clinical diagnosis
- A DRE is not routinely recommended to diagnose an anal fissure
- If the diagnosis is unclear or the spasm and pain make diagnosis difficult → refer for examination under anaesthesia
If a secondary anal fissure is suspected → further investigations are needed to identify the underlying cause
Unexplained anal fissures in children should raise suspicion of sexual abuse.
However, note that constipation or inflammatory bowel disease in children can cause anal fissures.
Lower GI Cancer Red Flags
Offer FIT to those with any of the following red flags:
- With an abdominal mass
- With a change in bowel habit
- With iron-deficiency anaemia
- ≥40 y/o with unexplained weight loss and abdominal pain
- <50 y/o with rectal bleeding and either of the following unexplained symptoms:
- Abdominal pain
- Weight loss
- ≥50 y/o with any of the following unexplained symptoms:
- Rectal bleeding
- Abdominal pain
- Weight loss
- ≥60 y/o with anaemia (of any cause; even in the absence of iron deficiency)
If FIT is +ve → refer with suspected cancer pathway (for colonoscopy)
Since June 2020, UK guidelines recommend FIT testing as the initial step for patients who meet the criteria for suspected colorectal cancer referral.
Only patients with abnormal FIT results proceed to colonoscopy. This represents a change from previous practice, where patients meeting referral criteria went straight to colonoscopy without prior FIT testing.
Management
Approach:
- Step 1 (all patients): conservative / general management
- Step 2 (if no improvement after 1 week): add on topical therapy
- Step 3 (if all pharmacological therapy failed): consider surgery
Conservative / General Management
Advise / offer the following to ALL patients:
- Ensure stools are soft and easy to pass
- Advise adequate dietary fibre intake
- 1st line: bulk-forming laxatives (e.g. ispaghula husk)
- 2nd line: osmotic laxative (lactulose)
- Anal hygiene
- Keep the anal region clean and dry to aid healing
- Advise against ‘stool withholding’ and undue straining during bowel movements
- Analgesia
- Paracetamol or ibuprofen if there is prolonged burning pain following defecation
- Avoid opioids, as they can cause constipation and worsen the symptoms
- Sitting in a shallow, warm bath several times a day, esp. after a bowel movement may help
- Consider a short course of topical lidocaine ointment to be used before passing stool in those with extreme pain
Topical Therapy
Only consider topical therapy if symptoms failed to improve after 1 week of conservative management / recurrent anal fissure:
- Step 1: rectal GTN ointment for 6-8 weeks
- Step 2 (if no improvement): seek specialist advice on alternatives like topical diltiazem
- Step 3 (if no improvement): consider botulinum toxin type A injection
Surgical Management
Gold standard: lateral internal sphincterotomy
- Most effective surgical surgery – 90-95% healing rates
- However, there is a risk of faecal incontinence
Surgery is considered the last resort in the management of anal fissure.
References