Paracentesis

Paracentesis is a medical procedure involving needle drainage of fluid from a body cavity, most commonly the abdomen. It is used for a number of reasons:

• to relieve abdominal pressure from ascites
• to diagnose spontaneous bacterial peritonitis and other infections (e.g. abdominal TB)
• to diagnose metastatic cancer
• to diagnose blood in peritoneal space in trauma
• to puncture the tympanic membrane for diagnostic purposes, such as taking a bacterial swab from the middle ear.

A related procedure is thoracocentesis, which is needle drainage of the chest cavity.

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Paracentesis for Ascites

The procedure is often done in doctors office or an out-patient clinic. In an expert's hands, it is very safe, although there is a very small risk of introducing an infection, causing excessive bleeding or perforating a loop of bowel.

During the procedure, patients are asked to lie down and expose their abdomen. After cleaning the side of abdomen with an antiseptic solution, physicians will numb a small area of skin and then insert a fairly large-bore needle (along with a plastic sheath) 2 to 5 cm to reach the peritoneal (ascitic) fluid. The needle is then removed, leaving the plastic sheath behind to allow drainage of the fluid. The fluid can be drained by gravity or by connection to a vacuum bottle. Up to 10 litres of fluid may be drained during the procedure. If fluid drainage is more than 5 litres, patients may receive intravenous serum albumin (25% albumin, 8g/L) to prevent hypotension (low blood pressure).

The procedure generally is not painful; patients require no sedation. As long as they are not very dizzy and maintain their blood pressure after the procedure, they can go home afterwards.

Ascitic fluid analysis

The serum-ascities albumin gradient can help determine the cause of the ascites. The ascitic white blood cell count can help determine if the ascites is infected.

Contraindications

Mild hematologic abnormalities do not increase the risk of bleeding.^[1] The risk of bleeding may be increased if:^[2]

• prothrombin time > 21 seconds
• international normalized ratio > 1.6
• platelet count < 50,000 per cubic millimeter.

References

1. ^ McVay PA, Toy PT (1991). "Lack of increased bleeding after paracentesis and thoracentesis in patients with mild coagulation abnormalities". Transfusion 31 (2): 164-71. PMID 1996485.
2. ^ Ginès P, Cárdenas A, Arroyo V, Rodés J (2004). "Management of cirrhosis and ascites". N. Engl. J. Med. 350 (16): 1646-54. doi:10.1056/NEJMra035021. PMID 15084697.