At a glance
Most anal fissures follow a predictable pattern: they occur at the posterior midline, they are caused by hard stools or constipation, and they respond to conservative treatment. When a fissure does not follow this pattern, clinicians describe it as “atypical.”
This is not a diagnosis of something serious. It is a clinical observation that prompts more careful assessment. This guide explains what makes a fissure atypical, what further investigation might be needed, and what it means for treatment.
What ‘typical’ looks like
To understand atypical, it helps to know what typical means:
- Location: Posterior midline (the back of the anal canal) — roughly 90% of fissures occur here
- Cause: Hard stools, constipation, or straining
- Appearance: A single, linear tear
- Response: Improves with conservative measures (stool softening, sitz baths, topical treatments)
- Patient: Otherwise well, no other significant symptoms
What makes a fissure atypical
A fissure may be considered atypical if any of the following apply:
Unusual location
- Lateral fissures (to the side) are less common and may prompt investigation
- Anterior fissures (at the front) are more common in women, particularly after childbirth, but still warrant attention if they do not follow a clear cause
- Multiple fissures in different locations are unusual and may suggest an underlying condition
Unusual appearance
- Fissures with irregular edges rather than a clean linear tear
- Deep fissures that appear to extend beyond the usual depth
- Fissures with significant surrounding inflammation that seems disproportionate
- Lack of a sentinel pile in what appears to be a chronic fissure (not always significant, but noted clinically)
Unusual context
- Fissures in young, otherwise healthy people with no history of constipation or straining
- Fissures that do not respond to standard conservative treatment after an appropriate trial
- Fissures accompanied by other symptoms: weight loss, diarrhoea, oral ulcers, skin changes, joint pain, or fever
- Recurrent fissures in unusual locations
Why investigation matters
The reason clinicians pay attention to atypical fissures is that some underlying conditions can present this way:
- Crohn’s disease — inflammatory bowel disease can cause anal fissures, particularly lateral or multiple fissures
- Infections — certain infections can cause fissure-like tears
- Dermatological conditions — some skin conditions affect the anal area
- Other causes — rarely, atypical fissures can be associated with other conditions that warrant assessment
The investigations are usually straightforward and are guided by the overall clinical picture. Not everyone with an atypical fissure needs extensive testing — the clinician uses their judgement based on the full picture.
What this means for you
If your clinician has described your fissure as atypical:
- Do not panic. This is a clinical observation, not a diagnosis of something serious.
- Ask questions. What specifically is atypical? What further investigation is recommended? What is the timeline?
- Follow through with investigations. The purpose is to understand your fissure better so it can be treated more effectively.
- Continue basic self-care. Stool management, hydration, and sitz baths are still appropriate while investigations are underway.
- Be honest about all symptoms. Mention anything else you have noticed — bowel changes, weight changes, other symptoms that might seem unrelated. This helps the clinician build the full picture.
Treatment approach
Many atypical fissures are treated with the same approaches as typical fissures — the difference is that the clinician monitors more carefully and investigates if healing does not progress as expected. In some cases, treatment may need to address an underlying cause alongside the fissure itself.