What have they ruled out? Have they tested him for a Urinary tract infection? How about a possible kidney infection or kidney stones? Have they done an abdominal ultrasound or tested his urine?

Has he done anything differently, such as strenuous exercise? Has he had any injuries to his back or anywhere else recently? Has he been on any medications?

Since none of the other doctors seem to be helping, take him to a urologist and have him checked again as soon as you can. Write down all his symptoms, when they started, what he was doing before that that was different or anything that happened, and if anything makes the pain better or worse. Also, write down your questions for the doctor.

I hope they find the cause very soon. Good luck. Let us know what the doctor says. Write back if you have any follow-up questions.