dog can't urinate, is bloated and we can't figure out why?

8 yr old 30lb dog, bloated, x-rays show bladder full , catheter inserted to empty bladder. Exploratory finds nothing out of the ordinary , no stones, tumors, lesions , masses or blockages Spleen is a bit swollen but not enough to be a concern. Blood work shows nothing that would cause this problem. Dog is catheterized 3 times since yesterday and bladder drained. Has been eating A/D , and has been getting IV fluids. Any suggestions would be greatly appreciated as all of us at the animal hospital have run out of options as to what to do next. This dog has been examined, had lab work done, had almost every organ in the body examined , x-rays and nothing has been found. We have wonderful Dr.s at work and it is so unusual that they can not find the problem, I am willing take any and all suggestions to work so we can help this poor dog.

Poor thing have you called any other doctors or clinics for advice?? I know they have web md do they have web dvm. Call a professor at a university that teaches veterinary medicine.

Any of the blood or urine testing show the SLIGHTEST abnormality in ANY area? Any detective work on what he/she may have ingested? Is he a stray, or someone's (pet) who would be able to give a history on him/her? I'm for contacting a vet school as well. Urethras can swell from infection in the pores lining the passage and prevent passage of urine, and there are medications specifically for this condition that have the ability to relax it so urine can pass. Infection in these pores does not always show up in a urinalysis. Have the vets tried a urinary specific antibiotic and a drug called Urispaz to see if it would help him/her (don't remember if that's exactly the right name, but it's close anyway)?Edit: Have they done a cardiogram?

Consider a muscle relaxer (robaxin/methocarbanol) although it only works with smooth muscle, it could be that the sphincter can't relax in order for this dog to pee. Otherwise it could be neurological, maybe the next step would be an MRI to indicate any brain lesions that would cause anuria. I'm interested in know your outcome regardless, if you don't mind keeping me posted. I'll try some more research and see if I can help more.