The first thing to do is get a measuring jug (not one you intend to use in the kitchen). Start recording times and volume when drinks are consumed and times and volumes of pee. Do this for about a week so you will have a good idea what is going on. From that you will know whether he is creating a lot of urine in the night, or if he creating a small amount and is just pissing out a little bit at a time.
I don't know how to solve over production of urine at night, apparently it is common in old age, but can be treated with medication.
If he is only peeing small amounts and not fully emptying bladder, I would consider Clean Intermittent Self Catheterization (CISC) once per night before bedtime. You will presumably need to get the NHS continence service involved to manage this
I made a post on it a few years ago.
Just a thought.I have a permanent suprapubic catheter on free drainage,my bladder capacity is less than 100mls. At night I attach a night bag and produce anything from 400 -1200 MLS overnight. On the nights when I forget to open the leg bag tap, I sometimes wake up the next morning to find only 400 MLS in the leg bag.
Does the bladder sense how full the bladder is and reduce urine production ? Do the frequent night time visits happen because the level gauge has packed up
I can't offer much by way of advice but can tell you that, three years after EBRT and 10 months after coming off three years of HT, I still have to get up at least three times a night. It drives me mad and I often feel washed out when I eventually get up in the morning. Should mention I am on Amlodipine, a calcium channel blocker, for hypertension and that can cause nocturia though I can't say for certain it's the cause of my problem. I don't drink any fluids any later than 9pm, usually earlier than that, it makes no difference. It's a mystery to me where the urine comes from!
It might be overactive bladder rather than anything to do with the PC or its treatment. Might be worth asking for a referral to the incontinence clinic for an assessment and possibly some bladder retraining
"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard