The drainage of ascites or peritoneal fluid from the abdomen.

Paracentesis is performed using an intravenous or peritoneal dialysis catheter and may be performed as an outpatient procedure or in the patient's home. Ultrasound-guided placement of the catheter is safer, and should be used where it is available.
It is usually possible to drain 4-6 liters of fluid, by gravity, over a few hours. Drainage for more than 6 hours is unnecessary, as the symptomatic benefit is maximal after the first few liters are removed.
Catheters left in place for longer periods of time increase the risk of infection and fluid loculation.
Hypotension or hypovolemic shock is uncommon in patients with malignant ascites, even though large volumes of fluid may be removed relatively quickly. Care must be taken with patients with hypotension or intravascular dehydration prior to the procedure.
The co-administration of intravenous plasma volume expanders or albumin has not been demonstrated to be of benefit in patients with malignant ascites.

Woodruff R. Palliative medicine evidence-based symptomatic and supportive care for patients with advanced cancer. 4th ed. Oxford University Press, 2004. p. 262.