Didn't get anywhere personally and they already tried reddit's version of tomt, so I hope someone can help. To cut the story short a person I know asked me to help them find a movie and here's what they remember, its not much but its what we got:
• The doctor got infected because of the patient he was working on.
• The son hitched a ride on his dad's car and stayed in the bathroom, watching through the ajar door.
• There's a behind shot of the prostitute sawing off his leg and lifting it up to examine it.
• After feeding him, the prostitute lays down on the same bed as the doctor to watch TV and eat pizza.
• The characters were all white, I think the doctor was stocky? I can remember exact details except maybe the prostitute had a ponytail?
• After the prostitute leaves, the boy exits the bathroom and the doctor finally notices him. I think he has a look of despair as the boy solemnly leaves the motel room.
• I think I watched this in the early 2000s and it was set in that timeframe.
I remember it being swathed in blue I think it was in color though, just a bit subdued?
Edit: I was mistaken. I'm lost too.
Cannibal Doctor?
Thought so too but sadly no