Despite recent findings suggesting that copeptin, a byproduct of AVP synthesis, might help predict AVP-D by reflecting the postoperative secretion of AVP [9–15], copeptine measurement has not yet been demonstrated as sharply discriminative in the diagnosis of AVP-D after TPS, which remains based on clinical (daily quantification of both water intake and output to identify polydipsia/polyuria) and laboratory values (daily, or twice-daily, blood and urine analyzes to identify hypernatraemia and decreased Na concentration/osmolality of the urine) [3, 7, 16–18]. Here, AVP is linked to Polyuria.