New Caregiver with a Question

Hello everyone....

My father is 87 and was recently diagnosed with urothelial carcinoma high-grade. His prostate is also very enlarged. One ureter it totally blocked and that kidney as withered. The other ureter is partially blocked. Even with all this, he is producing urine.

My question if anyone knows....the urologist put a catheter in. He said that would tell him if it's his bladder or the plumbing. But I don't understand this. If he doesn't see the urine output or it's not measured, how is this any different than dad going on his own in the toilet? I am lost to understand this.

He also had a lung biopsy today to see if it's the same as the bladder cancer. And we're playing mother may I with the insur co fighting for him to get a PET scan. He's already had a bone and a CT scan.

Thank you for any info and bless you all!