Postoperative syndromes are a particularly suitable topic for interdisciplinary gastroenterology. Internists and surgeons share the responsibility for the development of such syndromes and the challenges of their treatment. Diagnosis is also a joint task, both in the case of an individual patient with complaints and in the context of evaluating the success of surgical interventions. Postoperative syndromes have so far led a shadowy existence in the literature. The main reason for this may be that all subsequent diseases after surgical procedures have been too easily attributed to the surgeon. However, many postoperative syndromes are unavoidable consequences that are inherently linked to the surgical procedure. This book aims to provide an objective assessment. The primary concern of the editors is to provide enough facts for an informed discussion.