CAT scan and blood work showed nothing out of the ordinary except signs of a slight infection in the area where he hurt. The pain has subsided almost back to normal, so he has been discharged from the ER and is at home. The good news is there is nothing obviously wrong. The bad news is he wishes we had positively identified what it was.
He went in because the pain had been constant for 36 hours and made walking difficult without bending forward. Now he is walking normal but still feels some residual pain.