This document discusses peritonitis, which is an inflammatory or suppurative reaction of the peritoneal lining caused by an irritant. Common causes include bacterial infections from GI issues like perforation or pancreatitis, or non-GI related issues. The peritoneum functions to lubricate organs, absorb and exude fluids, perceive pain, and mount inflammatory and immune responses. Peritonitis can be non-surgical or primary, caused by infection without surgery, or surgical/secondary, caused by infection after abdominal surgery. Spontaneous bacterial peritonitis is a type of ascitic fluid infection seen in patients with cirrhosis and ascites, caused by bacterial translocation from the intestines. Risk factors, symptoms,