People as brusque as Dr. McCoy tended to have thick-skin. After all, this wasn't a social call. They were both intelligent professionals, he didn't need to spend time dumbing down medical information for them. McCoy was in the uncomfortable position of knowing that their marriage was on the rocks, and he certainly didn't want to intrude on their private time.
He nodded to Ben. It wasn't unlike something he might've said himself, if he weren't being awkward-polite Dr. McCoy. "I'll go. If you need anything, let your nurse know."
McCoy wasn't intentionally avoiding looking at Juliet, but everything he'd said had been directed at Ben, even when Juliet spoke to him. He would deny that, and any other awkwardness. Ben was the patient, after all!