Abdominal drainage versus no drainage after distal pancreatectomy: study protocol for a randomized controlled trial oleh Joerg Kaiser, Willem Niesen, Pascal Probst, Thomas Bruckner, Colette Doerr-Harim, Oliver Strobel, Phillip Knebel, Markus K. Diener, André L. Mihaljevic, Markus W. Büchler, Thilo Hackert