My 1 yr old cat has been hit by a car.?

he has bladder nerve damage and the vet is expressing him. He cant poo either. The vet said he needs a tail amputation to stop straining the nerves. I vistited him tonight and he ate and then got in his litter tray and started pawing and done a poo I am so pleased is this a sighn that his nerves maybe healing ? it has been 4 days. the nurse said he has not done that before.The vet said if he is in the tray and cant wee he is not getting better, but I think he is showing a glimmer of hope, what do you all think.