What Causes Bruises On Each Side Of Abdomen After Having Partial Gastrectomy?

Last December my husband had a partial gastrectomy to remove a very small ulcer that would not heal; it was not cancerous. Since that time he has had frequent bouts with pain at the incision site and last April a boil like lump appeared at the top of the incision which was lanced and confirmed to be infected with mrsa but his pain was gone until today. He is once again hurting at the incision site about 1-1/2 inches below where the "hematoma" was lanced. Also, two strange horizontal bruises have appeared on each side of his abdomen about 7 inches apart and in a line just a little above his navel. He is 80 years old and not active in any way that he could have bruised himself nor does he wear constrictive clothing. He says the pain is not a dull ache but neither a sharp stabbing pain and any pressure at the site makes it worse.