Folgetermin is quite alright, though my dental hygienist has been regularly giving "Recall-Termine" or simply "einen Recall" for this or that date to me for years already. The first time I asked her if she'd seen the Schwarzenegger movie :-)

"concerning the same complaint" leads me to "Nachuntersuchung", since the doc is going to verify the effects of his cure, isn't he ?

It is a bit more precise than only "Folgetermin", which is obviously correct.