After switching away from hydromorphone (Dilaudid) to Fentanyl, she seemed to have better luck emptying her bladder on her own. Apparently this is a potential problem with most of the stronger pain killers. She's still retaining 250 ml or so, and they say you feel like you need to go when you get above 300 to 350, but rather than doing the straight catheter every 3 to 4 hours, she opted to simply go to the bathroom every couple hours. So she didn't get much sleep, but this is progress.