Jacquelyn: Check out a previous thread that was titled 'Pee problems and ALS'
It's probably the bladder rather than the kidney causing the frequent urination.
One link in a previous discussion that was helpful to us was this:
http://www.alsa.org/patient/drug.cfm?id=646
Symptomatic Treatment of ALS - The ALS Association
Look for the clip on urinary problems, I think it's clip #4
There may be lots of reasons for frequent urination including infections, prostate problems etc. When those problems have been ruled out then something like Ditropan, as suggested in the above link may be the answer. It worked for a while for my PALS. When that was no longer helping we then went to an external catheter.
Icanmanz is right, it is the lack of abdominal muscle (and the lack of physical activity) that's a big contributor to the bowel problem.
I'd also say (from our experience) be cautious about adding too much soluble fibre or using frequent Colace capsules to solve the bowel problem unless your dad is drinking enough fluids. They soften and bulk the stool by drawing water into the gut and you may find the urine getting very concentrated if he has difficulty getting enough fluid.
For my PALS, pureed prunes (a spoonful with every meal) and a couple of SenkotS (i.e. Senokot combined with Colace) every other day seems to work well.
If he is constipated then that's probably putting pressure on the bladder. I'd sort out the bowels first!