I'm not 100% surw about exception on medical grounds. He can definitely submit paperwork for it. But in my understanding, USCIS will be far more interested in ties to the US he maintained.
Such as: lease in the US (or continuing paying mortgage towards property in the US), water, electric bills paid. Employment in the US, assets and savings in the US in bank accounts, brokerage accounts etc. Car in the US, driver's license showing US address. Taxes paid as required... Rest of family living in the US. Those would be things to prove he maintained life in the US.
I'd focus on these first and include medical surgery evidence as a secondary item.