Do you think taking lolagrace's advice and say you have a standing weekly appointment is sufficient? You can say it's a doctors appointment and you won't have phone or email access during that time. So long as it's your allotted lunch break they can't really argue with that. I do understand that office politics don't always adhere to those rules though, so you have to gauge it by what you think your boss will respond to. Maybe you can say it's for physical therapy if you think more info would help but you don't want to disclose anything. I don't think the type of medical appointment it is - such as PT versus psyhotherapy - will alter someone's opinion much.