When on dialysis you do not completely stop urinating when on dialysis.
However when on dialysis some people do not urinate as much as they used too and usually the person on dialysis will urinate in smaller amounts than they normally would.
Having kidney disease and being on dialysis can also sometimes cause incontinence and some people on dialysis wear adult diapers as protection from the incontinence.
A friend of mine who is on dialysis urinates less but she sometimes cannot hold her urine back like she used to be able to so she opted to wear adult diapers to contain the urine.
The adult diapers also help when she's on the dialysis machine because she has to be on the dialysis machine for 5 hours and in that time she would have to pee but she cannot get off the machine to pee.
So she wears adult diapers so she can pee in the diapers instead of having to worry about going to the toilet.