If that's the case, then this is a Urinoma I believe. Still though a creatinine of 4.54 and BUN of 56 is quite high but you're dad's urologist is right that creatinine can be inflated in this rare but unique scenario. BUN would be expectedly a bit higher if his creatinine were that high but not always. Cystatin C measurement can be another surrogate used to indirectly measure his true GFR. That hole wont repair itself unless the urologist diverts the urine elsewhere and hence the drain is needed. Bladder wont heal if there's continuous flow of any liquid, in this case urine, through the hole.
Thank you. I just got off the phone with his surgeon, and we were able to talk for about 30 minutes. He feels that there is a continued bladder leak and that we are likely to find that the fluid collection is high in creatinine. They are putting a drain in tomorrow and they'll test the fluid. If this is the case, his kidney function is likely not as poor as it appears, as his body is reabsorbing creatinine through his peritoneum. I did ask him to run a liver panel out of an abundance of caution and he agreed.