This book contains three chapters about peritonitis, which is an inflammation of the membrane lining the abdominal wall and covering the abdominal organs. Chapter One presents classification of postoperative peritonitis, describes symptoms, reviews the current understanding of the phases and stages of development and features of the disease, and discusses the usefulness of different prognostic scales for assessment of complicated intra-abdominal infections. Chapter Two studies assisted peritoneal dialysis, wherein a nurse goes to the patient’s home to perform the dialysis technique when the patient is unable to do it himself. Chapter Three discusses in detail different types of peritoneum infections, including their principles of diagnosis and treatment options.