She seemed to be a little off recently and I took her for an appointment to check her urine. It seemed OK but you can't always tell without an actual test. I was noticing a mucus discharge when I would hold her over the toilet. She sometimes has clear mucus and I don't worry too much. There can be mucus in urine, but frankly I suspected it was female and due to being in a diaper (not enough air, some dampness, hot weather, etc.). I became alarmed when I started to notice green in it. The vet found only slight evidence of a UTI but he put her on antibiotics to be sure. He also told me to give her acidophilus while on the antibiotics. I asked him how long I should give it to her and he said until at least a week after she finished her antibiotic, but I could also give it to her for life, this might be female. Finally, someone has said this discharge might be female, and not bladder related!
So following his instructions, we completed the antibiotic, she still had the discharge, and I continued the acidophilus and sure enough, it went away. I was simply taking the the capsules apart and sprinkling one on her kibble at mealtime. Then we finished the bottle of acidophilus, I went to the store to get more, they didn't have the kind we bought before, so I decided not to get any. Now it is a couple of months later and I am seeing the discharge again. So I went to another store and bought whatever kind they had and am giving it to her.
She has a combination of things besides wearing a diaper during the daytime, which include the way waste collects in her bottom (rectal vault), how the well-formed stools sometimes sit sideways inside her and come out sideways during expressing due to being bunched up (this may be stretching her rectum right there), and her particular method of walking is by bouncing on her bottom (probably bouncing any collected contents around inside, too). But having acidophilus in her system, which I assume(?) passes through her GI tract in her stools, seems to help the discharge.
Whatever the explanation, it is making a difference, and all I can think is, if anyone has a paralyzed female dog with a discharge, it's still a good idea to check for UTI to be sure it isn't mucus from the bladder, but if it isn't then ask the vet if acidophilus would help.