Anal fissures (GI) Flashcards
Define an anal fissure.
Longitudinal or elliptical tears of the squamous lining of the distal anal canal characterised by pain on defecation and rectal bleeding
Describe the aetiology of anal fissures.
- hard stool tears anal skin at dentate line
- alternate theory: ischaemia in anterior/posterior midline of anal skin + deficiency in NO synthase pathway –> spasm of internal anal sphincter (when hard stool is passed, not sufficient blood supply to heal split skin)
What are the first and second most common GI complications of pregnancy?
- haemorrhoids
- anal fissures
How can anal fissures be classified by duration?
- acute: <6 weeks
- chronic: >6 weeks
Where can anal fissures occur?
- primary anal fissures are typically caused by constipation:
- 90% posterior midline
- 10% anterior
- a lateral anal fissure suggests a secondary cause (e.g. Crohn’s) and requires further investigation
- additional Hx of change in bowel habit, weight loss and blood in stools in young-middle aged adults would require an urgent referral to secondary care
What are the clinical features of an anal fissure? (5)
- pain on defecation
- tearing sensation on passing stool
- fresh blood on stool/paper - bright red rectal bleeding
- anal spasm (and itching)
- intermittent
What might be seen on examination of an anal fissure? (4)
- fissure visible on retraction of buttock - indurated (hardened) edges and visible internal anal sphincter fibres at its base
- marked spasm of sphincter muscles
- sentinel pile (rare)
- significant tenderness makes DRE unsuitable
How might someone describe the pain of an anal fissure?
Severe pain on defecation “like passing broken glass” - pain may continue for 1-2 hours and can be burning
What are some risk factors for anal fissure? (6)
- middle age
- hard stool / constipation
- pregnancy (3rd trimester)
- opiate analgesia (associated with constipation)
- IBD
- STI (e.g. HIV, herpes, syphilis)
How are anal fissures diagnosed?
Clinical diagnosis - no tests necessary at initial presentation
When is anal manometry done for an anal fissure?
Used to determine second-line treatment in resistant fissures - determines resting pressure (could be low)
When is anal ultrasound done for an anal fissure?
In patients with suspected anatomical deficits - exclude secondary cause of anal fissure or alternative diagnosis with anoscopy, colonoscopy, sigmoidoscopy
What are some differential diagnoses for anal fissure? (8)
- Crohn’s disease (lateral fissure)
- sarcoidosis (lateral fissure, respiratory symptoms)
- TB (lateral fissure)
- HIV (IV drug use)
- lymphoma
- syphilis
- anal carcinoma
- perianal abscess (spiking temperatures)
How do we manage anal fissures on presentation?
- conservative treatment: high fibre diet, adequate fluid intake, sitz baths, topical analgesia (lidocaine), topical anaesthetics, lubricants
- bulk-forming laxatives e.g. docusate sodium (if not tolerated –> lactulose)
How do we manage anal fissures that have gone 1 week or more without improvement?
- topical glyceryl trinitrate (GTN) for vasodilation to increase blood flow
- 6-8 weeks for re-epithelialisation of fissure
- lowers anal resting pressure but need to limit dose due to headache (cerebral vasodilation)
- topical diltiazem (alternative if headache not tolerated - often used 1st line due to better side effect profile)
- if topical GTN not effective after 8 weeks: secondary care referral for surgery/botulinum toxin
