Kidney issue- neurogenic bladder.

Hi my cousin is suffering from urine leakage. 1 year ago when we started his treatment his creatinine was 18 , which reduced to 8 and now it is 13. Doctor told that he had neurogenic bladder. He would earlier pee during sleep, couldn't control it and it was told that some nerver that controls urine was paralysed or missing. For the past 8 months he is able to control urine flow, doesn't pee even a single drop during sleep, can control the urine flow and can sense the urge to urinate too. Given that he couldn't sense the urine flow doctors said he wouldn't survive and dialysis would only extend his lifetime for few months. Even if we did a kidney transplant his condition would damage the newly transplanted kidney. But he says that he can feel and control the urine flow now. We are looking to cure the urine flow issue and if it goes well only then we can go further for kidney transplant. Can surgeries like sling surgery or sphincter surgery help? Or can you suggest some other surgery?