Brief Answer:
Abscess vs hematoma

Detailed Answer:
Dear patient,

Thanks for your query. Given the location and size, the most common acute or sub-acute causes would include a gluteal or perianal abscess, or a hematoma (blood collection). Differentiating between both can be tricky and requires physical examination and probably, if the suspicion is correct, aspiration and drainage; some of the hematomas are left to resolve on their own, particularly if they have been caused by trauma. I would highly recommend you to see your physician so he can examine and determine if aspiration is needed.

Yours truly,

Dr Brenes-Salazar MD
Mayo Clinic MN

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Brief Answer:
Variable depending on cause

Detailed Answer:
It is not life threatening but you should see your doctor soon, because if it is an abscess, then it requires drainage and perhaps antibiotics; if it is a hematoma, many times it is excepted to reabsorb, but it can take from weeks to months. An abscess in that area is caused by translocation of colonic bacteria into the tissues, a hematoma results from bleeding into the muscle, either by trauma or spontaneously in people taking blood thinners

Truly yours

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