possessives - How to indicate possession when using abbreviation "Dr."

I often run into a case where I need to say I have a doctor's appointment, but how would I properly punctuate it if I wanted to use the abbreviation Dr. instead of the word doctor? Dr.'s appointment looks strange to me.

Answer

Basically, the word doctor is a noun, and is the one to be used in any regular form of speech or writing.

Dr., on the other hand, is an honorific. Like Mr., Mrs., or Prof., it isn't meant to be used as a noun at all.

To answer more directly, there is no proper way to use the abbreviated form to indicate possesion, as it isn't a noun.