Can a Seroma/hematoma Be Absorbed by the Body on Its Own...how Long Will It Take?

I agree with the other doctors in that this needs to be drained.  If you waited it could take a very long time for it to go away on its own, if it even does completely go away.  I would address these concerns with your plastic surgeon again. 

Thank you for your question. A hematoma can be very mild or very pronounced in its presentation. A mild one may induce slightly more swelling and increased bruising and will likely resolve on its own. A more severe hematoma can result in dramatic asymmetry in terms of swelling, feelings of light headedness due to loss of blood, severe bruising, and can be rapidly growing. If you every experience the latter, then I would contact your surgeon immediately and if you have trouble, you may even go to the ER. Larger hematomas often have to be surgically drained.  This would be an example of a larger hematoma and if it does not show evidence of it resolving quickly, then I would recommend getting it drained.

Thank you for the question. It is imperative
that you see your physician immediately if you currently have a
seroma/hematoma. The accumulation of the fluid will prevent things from
properly healing, thereby compromising your results substantially. Ideally you
should have it drained and perhaps several times as they can come back.
Only small seromas resolve on their own and can take several weeks. I
hope this has helped.