The objective of my PhD is to evaluate whether pre-operative composition of the intestinal microbiota and/or post-operative changes in microbiota composition influence the intensity of acute PSP and the risk to develop persistent PSP in patients undergoing non-abdominal surgery. Specifically, we hypothesize that composition of the intestinal microbiota could be an important factor influencing the susceptibility to develop peripheral and/or central sensitization and, hence, that pre-operative composition of the intestinal microbiota and/or post-operative changes in its composition could be an important determinant of the severity of acute PSP and the risk to develop persistent PSP.