wife of 41,
I have had a renal lasix scan. Here is a big heads-up on that:
They had me drink a lot of water. Then, I was prepped and put on the scanning table. For the first 20 minutes, I could see the flow through my kidneys on the screen -- interesting. Then, they infused me with the lasix, for the next 20 minutes. The flow really increased! By the time I was done, I was dying to go to the bathroom. I went again in the hospital lobby. Then, on the way home (my wife was driving and it was a 15 minute drive), I told her I could not make it home without peeing. We had to stop at a fast food joint that was only 5 minutes from our house. Safety tips: 1) Hang around the lobby and use the bathroom multiple times before leaving. 2) Have an empty jug in the car just in case. Here is the kicker: I had a nephrostomy tube and a leg bag for one kidney. The other kidney was emptying into my bladder. I was filling both my bladder and the bag! Without the bag, I am sure I would have had an accident. Have him wear dark pants.
More seriously -- other discussion questions for the doctor: Is he having any flank pain that might indicate a blockage of some sort? Have they did an ulltrasound or CT scan to look for hydronephrosis?
Good luck!