Could be blunt force trauma to the kidneys resulting in shutdown of the kidneys. You didn't say if he is getting IV fluids to keep his urinary output to at least 30/ml per hour. Were there any CT scans done of the abdomen especially of the Kidneys? or a KUB xray(kidneys, ureter and bladder). Did he have ultrasounds of his abdomen and the retroperitoneal area to check for internal bleeding? Does he have blood in his urine? Does he have a foley catheter in his bladder to keep up with urine output. If not, why not. This is standard trauma protocol. If not, he could have urinary retention. Have the nurses or Dr. check to see if his bladder is distended? What was his blood count, CBC, CMP and PT & PTT?
If he has muscle damage, he could have rhabdomyalysis, muscle damage can cause a build-up of myoglobin, clogging the kidneys. And due to the type of trauma he received, was his spine and spinal cord intact? How long before this urinary problem was the accident? There are many things that could be going on here.
ER RN 30+ years.