attending physician; physician in charge; (one's) family doctor
入院中に主治医と相談した。
I consulted with my attending physician during my hospital stay.
主治医の指示に従って薬を飲んだ。
I took the medicine following my attending physician's instructions.
手術の前に主治医から詳しい説明を受けた。
I received a detailed explanation from my attending physician before the surgery.