Organ processing was the Vidiian term for extracting the organs of an individual and transplanting them into a Vidiian body to replace the organs which were affected by the phage.
On Avery III, a base of the Vidiian Sodality, prisoners who were weak or ill were taken to organ processing. In 2371, Chakotay pretended to be a guard taking Tom Paris there so they could rescue B'Elanna Torres. (VOY: "Faces")