Definition of Paracentesis

Paracentesis: The removal of fluid from a body cavity using a needle, trocar, cannula, or other hollow instrument.

A paracentesis may be diagnostic or therapeutic as, for example, in ascites where there is free fluid in the abdominal (peritoneal) cavity. If the cause of the ascites is uncertain, diagnostic paracentesis is done in order to obtain fluid to examine. Therapeutic paracentesis may then be done to remove more fluid, as part of the plan of treatment.

Paracentesis of the chest cavity is called a thoracentesis.