My Friend, Who Is On Dialysis 1 Year Now, Slipped

My friend, who is on dialysis 1 year now, slipped on the ice & fell landing on a stair right on his left-side kidney. It happened @ 11am today. He went to dialysis and told the techs there & of course, they told him to go to the hospital. He does not want to go.
He hurts on the lower left backside around the kidney but could be his ribs too. It hurts when he does just about anything- breathing, coughing, bending, lifting, etc.
If he did injure his kidney what should we be looking out for that is a sure sign he needs to go to the hospital?