Anal Fissures


Anal fissure

This guideline applies to situations where the diagnosis of anal fissure is likely or confirmed. If diagnostic uncertainty, please see the guideline on "Undiagnosed Rectal Bleeding".



Anal fissures can be:

  • Acute: < 6wks
  • Chronic: > 6wks; a “sentinel tag” may be seen
  • Primary: Believed to be due to spasm after defaecatory trauma and poor perfusion/poor healing.
  • Secondary: Due to underlying cause, e.g. IBD, sexually transmitted infections, sexual abuse, rectal malignancy, drugs(nicorandil is a potential cause of unusual perianal fissuring and ulceration) and pelvic floor disorders.


Primary fissures are located at the posterior and anterior anal midlines(90% females, 99% males) and are benign. Secondary fissures are oftenlocated outside of the midline, and if associated with skin changes or inflamed skin tags should raise clinical suspicion of IBD (though is a very rare initial IBD presentation).

Typical Anal Fissure


Alternative causes for acute anal pain

Acute anal pain requires a face to face consultation for examination to exclude perianal sepsis or malignancy. In extreme circumstances admission may be required.

  • Acute perianal sepsis: usually presents with obvious swelling and tenderness starting on one side of the anus but can spread to the other side (horseshoe pattern). Sometimes it may not be obvious from the outside (if there is an intersphincteric abscess). Patients find PR examination unbearable and have constant pain with recent onset. There may be fever, tachycardia, deranged BG in diabetics. Patients with perianal sepsis should be admitted.
  • Malignancy: is rarely painful unless it is very advanced (and very obvious). Anal malignancy typically is noticed due to bleeding or irritation and may be an ulcer or an ‘odd uneven anal lesion’ akin to a bizarre skin tag.
  • Thombosed haemorrhoids: are a common cause of acute anal pain and evident externally.

Thrombosed Haemorrhoid                                                                     Ischiorectal Abscess (Advanced)

Anal Cancer                                                                                           Anal Cancer