Indications for Paracentesis Diagnostic paracentesis In patients who have peritoneal fluid that is new or of uncertain etiology In patients with ascites and symptoms such as fever or increased pain that suggest possible infection of the ascitic fluid (eg, spontaneous bacterial peritonitis) Therapeutic paracentesis To alleviate symptoms, usually dyspnea or pain caused by large-volume ascites Many causes of peritonitis are surgical emergencies and do not require paracentesis.