1wk post lumbar L4 and L5 back surgery. Today dark urin and dark vomit... Both coffee color. Sore swollen belly. What could it be.

Stomach bleed. Please get to be seen immediately by the family dr. Or go to the nearest emergency room immediately. You need to be treated for a possible stomach ulcer with bleed especially if you have been taking anti inflammatory medications or it could be a stress ulcer.