Update: Ludo never peed yesterday so we took him back to the animal hospital last night. They used a catheter and he apparently peed about 1/2 liter. Also, the vet on duty felt he may have an infection due to the smell. Ultimately, that was a relief. However, he still has not peed today as of this writing. I fear we may have to go back to the vet tonight again. We have taken him out twice...I carried him to several different locations in our backyard and down the street (thinking the scent of other neighborhood dogs might inspire him). Still, nothing. We held him up patiently and he seems to just want to lay down.  I allow him to lean on me or the fence or i have manually held him up under his chest...still nothing. I think we are both getting discouraged and concerned. We have called the vet a few times and have yet to hear back. Ugh...

Thanks for response. Ludo weighs around 95lbs and is on 300 mgs every 8 hours. 100mgs of Trazodone every 8 hours. Carprofen 100mg every 12 hours. Cefpodoxine 200mg once per day. 

Yesterday around 430 he peed on himself outside. He hasn't since then though he seems more comfortable hopping around today. 

Ludo is doing much better this week. He is hopping around the yard a little bit and we have been able to decrease his pain meds pretty significantly. This evening he goes in to have his bandage changed again and the wound inspected. 

I was able to go back to work this week as my wife is now able to get him out to the yard using the webmaster harness . Fingers crossed. I think we are slated to start chemo next week if all goes well this evening. Tks.