I would suggest to your brother that he stop eating salt
immediately. That means: No more putting salt on food; no more salty prepared foods or junk foods. The most salt he should have is what you get in white bread, say. You're on a renal diet yourself; you can advise your brother how to change his food habits.
You can suggest the Table Tasty salt substitute till he gets accustomed to eating foods without salt. And doing that doesn't require any insurance claims.
What's causing the ankles to swell is fluid retention. And it's likely that your brother still has some residual kidney function, but the kidneys can't control sodium like they used to. With much lower sodium intake, even damaged kidneys can still excrete quite a bit of urine. It's worked great for me even though I have ESRD now.
I'll bet that within 48 hours after stopping all salt intake, your brother will start making tremendous amounts of urine, and the ankle swellings will subside. He'll have less thirst and he'll drink much less water too.