ok - just found your other thread -
it does sound like a kidney issue and that can be very very painful - Damson had a terrible time with his kidney stones, and Bramble with her bladder stones the same. Like a switch marked PAIN had been switche don in their heads - it was awful to see. and so sudden.
depending on weight of rabbit you may want to ask vet about an 'emergency' one off higher metacam dose . .
or ask about alternative painkiller (ketamine or vetergesic) by injection.