LOng-term follow-up after liVE kidney donation (LOVE) study: a longitudinal comparison study protocol - Janki, S; Klop, KWJ; Kimenai, HJAN; van, de Wetering J; Weimar, W; Massey, EK; Dehghan, A; Rizopoulos, D; Voelzke, H; Hofman, A; Ijzermans, JNM (BMC NEPHROLOGY, 2016)