What solution for elderly husband who poops while he urinates?

Sitting down to urinate is the practical answer. I agree that some men will fight that, but unless cognition is at a level where he can't understand what's happening, hopefully he'll cooperate. I would suggest, however, that he see a specialist about this issue. It's possible that something can be done to help him.
Take care,
Carol

Sitting down on the toilet to urinate helps a great deal. New habits are hard to get started, hope he is agreeable. Some men believe that masculinity is about standing up to urinate, so he may be reluctant.