"The doctor calls his grandson."
Translation:הרופא קורא לנכד שלו.
The Hebrew translation should allow for a male doctor. There is nothing to suggest that "his" does not refer to "The doctor".
The patient is an old man; he's seriously ill; perhaps his son or daughter is dead or unavailable, maybe lives in a distant country. Let's say he's a widower, or divorced. So his next of kin is his grandson. The doctor needs to tell this grandson something important about her patient's condition. She wouldn't phone her own grandson for that, even if she has one: she'd call the patient's grandson.