Dear Lisa, Tummy tuck surgery is a big procedure with large wound area that is third spacing (losing fluids) significantly after surgery. Consequently, you need to drink lots of fluids to avoid dehydration. In my practice I recommend to my patients to drink water or Gatorade , 8 ounces an hour while awake, for the first 48 hours after surgery. Urinating is a good measure of your hydration, so the more you drink the more you urinate and the better it is for you.It also forces you to ambulate (go to the bathroom) , which helps, together with hydration, to prevent blood clots. Always check your urine color , to make sure that it is clear. When it is yellow, it means that you are not drinking enough. If you can't urinate after surgery, it might be due to bladder spasm, resulting from anesthesia or narcotics, which require immediate attention and possibly insertion of urinary catheter in the emergency room. I hope this helps you, Best of luck, Dr Widder