Hi welcome to health care magic forum.
It is hard to say without documentaton but draines are usually palced because surgeon expects some fluid accumulation in abdominal cavity. so drainage
isnt something strange and unusual and in many surgery it can be detected. if this is less than 100ml per day then it isnt anything worrying and there is no need for specific teratment but wait an see. If drainage persist it can be sign of ascites
accumulation in peritneum,infection or some other rare disorders. It is important that there is no blood or pussy fluid.
Hope I have answered your query. Wish you good health. regards