Patient Confidentiality and Powers of Attorney?

How do powers of attorney for health care and client confidentiality co-exist? This question came to my mind while reading an article in the Wisconsin State Journal over the weekend. Apparently a Middleton man is suing his physician and others after the doctor called his mother (following surgery) and disclosed the patient was HIV positive. Asserting the doctor violated state law, the patient is now suing. What I find interesting is that the article does not mention whether the man's mother was operating with authority established in a power of attorney for health care. If so, it raises the question of whether a patient maintains confidentiality....I'll be watching this case and looking at my own POAs more closely.