Is a diuretic safe 10 days after surgery?

Maintenance of water after trauma such a surgery is a normal physiologic response. As long as they fluid retention is not excessive I would not prescribe a diuretic.

Please talk to your surgeon to find out if a diuretic is safe for you. Normally, I wouldn't advise it because your body will naturally work on reducing swelling. You can try cutting back on sodium, drinking plenty of fresh water and going to the washroom regularly, as well as leisurely move around to keep your circulation going.

Generally, I do not find the use of diuretics necessary/ helpful in your situation.  On the other hand, their use can be potentially dangerous, given associated electrolyte alterations… Do not use any medications unless prescribed by your physician. Best wishes.