This is my foster bun Magnus -

He arrived in the rescue with a urinary infection, an abcess on his jaw and he is not able to hop like normal bunnies.

I got him bonded with one of our long term bunnies who he is mad about (dont think he has ever had a partner before).
Our vet has been great and we have managed to reduce the abcess to nothing and get rid of his urinary infection with Depocillin injections and marbocyl.
However this seems to have left him with another problem. About every 2 days he is absolutley caked in poos. Each poo is well formed but is stuck together and it sticks to him. Its almost like he doesn't poo every day but he saves it up for a couple of days and then it all floods out. The vet and I originally thought it might be the way he holds his back end because he doesn't hop but I am not sure.
He has had 28 days of Lapizole (along with my 9 other buns!)
We have tried glucosamine, and metacam incase it is a joint thing - no improvement.
We did a trial of zantac (just incase it was a gut infection) and he is on 4weekly injections of B12 - still no improvement
So now we have changed antibiotics and we are giving him septrin - no improvement.
I am washing his bum every couple of days and in this weather using a hairdryer to dry him out. I am trying a bit of vaseline on his bum too to help stop the poo sticking.

But I am at a loss. It really upsets me to see Magnus like this. He is such a lovely rabbit and tolerates any treatment we give him really well.
So I was hoping someone here might have any ideas or experiences of something similar that I could share with our vet.