Hi! Many thanks for your question on eHealth forum!
I am so sorry to hear about all this. MRSA can turn serious. It is common in diabetes, low immunity as in cancers and AIDS, and in people who use healthcare and public facilities a lot. Hence since you have developed an abscess earlier too and then a sinus, you should be tested immediately for diabetes and AIDS.
Well sinus develops when an internal portion of the abdomen comes in touch with the skin. If the sinus is close to the laproscopy site or the incision and drainage site, then this could be the cause. The first laproscopic surgeon may or may not have seen the sinus depending on what he was suspecting and looking for.
MRSA is monitored by a culture and sensitivity test done on the swab collected from the site. This tells which antibiotic will act against it and how much infection is present. Blood sugar is kept under control and good hygiene and cleaning of wound is done. If not kept in control, this infection can damage any internal organ and cause life threatening systemic infection.
If the sinus has been treated, then a reconstruction of umbilicus can be tried for cosmetic purposes. You should consult a wound clinic and a cosmetic surgeon for proper management of this case. Hope this helps. Take care!