Perianal Haematoma

The Concept

A perianal haematoma — also called a thrombosed external pile or 'acute painful pile' — is a small subcutaneous haematoma at the anal margin, caused by the rupture (and thrombosis) of a small vein in the external haemorrhoidal plexus, typically after an episode of straining. Despite its alarming pain, it is a benign, self-limiting condition.

Clinical Features

It presents as a sudden, painful, tense, tender, bluish-purple lump at the anal verge — the pain is caused by the tension of the clot within the sensitive perianal skin. It is easily recognised on inspection as a smooth, dark, 'dome-shaped' swelling at the anal margin.

Management

The natural history is spontaneous resolution over a few days to weeks as the clot is absorbed. Management depends on timing: if the patient presents late or the pain is already easing, conservative treatment (analgesia, warm sitz baths, stool softeners) is sufficient; if the patient presents early (within about 48–72 hours) with severe pain, evacuation of the clot under local anaesthesia gives rapid relief.

A Note on Distinguishing It from a Prolapsed Pile

It is useful to distinguish a perianal haematoma from a prolapsed, thrombosed internal haemorrhoid. The perianal haematoma is a discrete, dark, smooth lump at the anal verge arising from the external plexus, whereas a prolapsed thrombosed internal pile is a larger, more circumferential, oedematous mass originating above the dentate line. The distinction matters because the small perianal haematoma is easily and safely evacuated under local anaesthetic when acute, whereas extensive thrombosed prolapsing piles are usually managed conservatively first.

The Bottom Line

A perianal haematoma is a benign, self-limiting thrombosed external vein at the anal verge, managed conservatively when settling or by clot evacuation under local anaesthetic when acutely painful.

A Note on the Natural History

Understanding the natural history reassures both clinician and patient: left alone, the clot in a perianal haematoma gradually organises and is reabsorbed over one to two weeks, occasionally leaving a small residual skin tag. Because the condition is self-limiting, the decision to intervene rests entirely on the severity and timing of the pain — early evacuation for severe acute pain, conservative management otherwise. Explaining this benign course is itself a valuable part of treatment, preventing unnecessary anxiety about the alarming-looking lump.

Presents as sudden severe pain with a tender blue perianal swelling.

• Perianal haematoma ('thrombosed external pile', 'acute painful pile') = subcutaneous haematoma at the anal margin from a ruptured/thrombosed perianal vein, usually after straining.
• Sudden, painful, tense, tender, bluish-purple lump at the anal verge.
• Self-limiting (resolves over days to weeks).
• Conservative (analgesia, sitz baths) if presenting late; evacuation of clot under local anaesthesia if early (<48–72 h) with severe pain.