do you have an emergency vet you can take him to? this sounds like a neurological issue, either a disk problem or an sudden injury. does he exhibit any pain?

IF it is neuro, he needs to be seen immediately. many times, a course of steroids can help reduce inflammation/swelling which is what is needed but, the sooner the better!!

best of luck, i know it's a scary thing. my male corgi suffered from degenerative myelopathy which causes hind end paralysis and while it comes on very slowly over a period of months, it was horrible to see.

your best bet is to get him to an e.r. NOW.

I agree with nina. The longer the wait the higher the chance that the damage will be permanent.
Call around until you find an ER..........

A similar thing happened to our pug a few months ago. She was fine in the morning and within a few hours she was completely paralyzed in the back end with some problems with her right front leg. Took her to a neurologist who guessed that the problem was in her neck. Could have been a small blowout or could have been something major. Went back to our regular vet who put her on a muscle relaxer and strong steroids. We also started K-laser treatments on her neck. Within a week she was back up, a little, and was able to piddle by herself. Very slowly she improved and to this day we still do the laser treatments once a month. She's not 100% back to her old self but, she's able to walk. Mind you, it was VERY rough those first few days. Had to hold her while she did her business, set up a padded penned area to keep her safe, held her water bowl and hand fed her, carried her from room to room so she was always in our sight. Today we have carpet runners throughout the house since we have tiled floors. I use carpet runners or small rugs to make paths for her to travel the house. I have objects that I use as steps so she doesn't jump up or down from anything. Most times we lift her up and down. She did have one small set back during this time. We immediately took her back in and did another dose of steroids. If I notice any change with her walking we bring her in for another laser treatment (cost is $22 a session). Don't give up on your baby. A small, and cheaper alternative could be just some medications and the k-laser treatments (google it and see what this is)

We had a similar experience with our older dog, although the onset was a little more drawn out so we were able to get her in before she was completely paralyzed in the rear. Good thing, too, since she is a 90 pound dog.
The vet did xrays and found some severe arthritis in her back, which was exacerbated by some swelling (probably due to an unknown injury). A course of steroids and followed up by anti-inflammatory meds and she is doing well - that was over 2 years ago - a long time for a dog her size.
Good luck!

Take her to an emergency vet! It sounds like a spinal cord injury. There is a short time frame during which steroids need to be given to reduce swelling and further nerve damage to avoid permanent damage to spinal cord.

Patricia Smith , my dog is doing the same thing took him to the vet got shots and meds still no better, what was wrong with your dog?