About Perianal Haematoma
A perianal haematoma, wrongly called a thrombosed external pile or external haemorrhoid, is a collection of blood within the skin around the anus. It is due to a ruptured blood vessel within the skin usually caused by some minor trauma such as something hard within the stool. Patients can be forgiven for mistaking a perianal haematoma for a haemorrhoid but GPs certainly can’t!
The typical history is a moderate sized swelling appearing at the anal verge which is tense and intensely painful. Patients who have haemorrhoids by contrast, give a protracted history (many years) of swellings that are prolapsed (come out) and then reduce. A perianal haematoma cannot be pushed back inside. Its origin is on the outside where it stays. Most of the swelling and the pain relate to toxins that are produced by the blood within the tissues, causing inflammation.
The options rest between either conservative (do nothing) or incision and evacuation. If left alone, the haematoma will resolve by itself in due course. This usually takes a couple of weeks but the patient suffers at least a week of continued pain and swelling. The sensible solution is an incision and evacuation within the first seven days. This is an office procedure and involves injecting local anaesthetic into the overlying skin and incising the haematoma and evacuating the clot. This provides instantaneous relief. The wound is left open to allow the drainage of any further collection of blood (unlikely) and this spontaneously closes within a day or two. In the meantime the patient simply needs to keep the area clean with regular perianal hygiene in the form of soap and water and to wear a pad until it is dry.