Transfer of FRozen Encapsulated multi-donor Stool filtrate for active ulcerative Colitis (FRESCO): study protocol for a prospective, multicenter, double-blind, randomized, controlled trial. - Stallmach, Andreas; Grunert, Philip; Stallhofer, Johannes; Löffler, Bettina; Baier, Michael; Rödel, Jürgen; Kiehntopf, Michael; Neugebauer, Sophie; Pieper, Dietmar H.; Junca, Howard; Tannapfel, Andrea; Merkel, Ute; et al. (Trials, 2022)