Just a guess.

in a medical context, you may want to consider translating "visita" as examination (visita medica); as to "anticipata" it depends entirely on the context, as we don't how it relates to the rest of the sentence.

saluti

paola l m

Seems the examination for one or another reason may have been done precedentely than originally scheduled/planned? Perhaps you can find a hint in your text.

Certainly is an odd term, and I think it probably means that the appointment was moved up.
However, "anticipare" is also used commonly to mean "notify in advance".
Thus, if this is on the doctor's report as a comment (to himself or to colleagues), "visita anticipata" could mean that the patient was alerted as to the fact that another appointment would be required.
Long shot on this one, but who knows?