The Base hospitals were in and around Salonika, which was the Base Area. Depending on which part of the Vardar/Doiran area he was in at the time, he would have been brought to the Dudular Military Railway Station down the Monastir or Constantinople lines.
Period maps, produced by Austria-Hungary, of the Balkans are available, free, HERE
. Maps 40-41 and 41-41 cover the XIIth and XVIth Corps areas as well as the area around Salonika.