Secondly, consider scheduling this patient the first thing in the morning or the first appointment in the afternoon to minimize his contact with other patients in the waiting room.
However, if the complaints continue, I think you are obligated to politely inform him of the complaints. Let him know that because of the importance of patient privacy, it would be better if he did not quiz people about their reason for seeing the physician.
Some other things to keep in mind to help maintain patient privacy:
Be aware of your voice volume when speaking on the phone to patients. Information could be overheard in the waiting room. A good way to check this is to sit in your waiting room and listen to what waiting patients hear.
Put phone nurses in private areas to respond to calls, not in areas where waiting patients could overhear.
Keep the chatter in the halls to a minimum. A lot of conversation in the halls can be heard by patients sitting in exam rooms. Again, go sit in one of your exam rooms with the door closed for a while and listen to what can be heard in the room. And never start asking patients questions until you have them in a room with the door closed.
Place charts in the chart holder with the name facing the wall. This protects the patient's information from being seen by people walking in the halls.
Make sure all directions and follow-up information, such as lab work, prescriptions, diets, etc. are taken care of in the patient room, not at a central desk in the more public areas in your office.
And if you are the patient in the waiting area who is asked about why you are seeing the physician, it's OK to politely say you don't wish to discuss your health issues with strangers. That's a nice way of telling them it's none of their business.