Paracentesis (from Greek κεντάω, "to pierce") is a form of body fluid sampling procedure, generally referring to peritoneocentesis (also called laparocentesis or abdominal paracentesis) in which the peritoneal cavity is punctured by a needle to sample peritoneal fluid.
The procedure is used to remove fluid from the peritoneal cavity, particularly if this cannot be achieved with medication. The most common indication is ascites that has developed in people with cirrhosis.
Indications
thumb|[[Cytopathology of peritoneal fluid from paracentesis (Pap stain), showing typical features of adenocarcinoma]]
It is used for a number of reasons: although there is a small risk of infection, excessive bleeding or perforating a loop of bowel. These last two risks can be minimized greatly with the use of ultrasound guidance.
thumb| Small fluid collection in [[Morison's pouch]]
Procedure overview
The patient is requested to urinate before the procedure; alternately, a Foley catheter is used to empty the bladder. The patient is positioned in the bed with the head elevated at 45–60 degrees (Fowler's position) to allow fluid to accumulate in lower abdomen. After cleaning the side of the abdomen with an antiseptic solution, the physician numbs a small area of skin and inserts a large-bore needle with a plastic sheath in length to reach the peritoneal (ascitic) fluid. The needle is removed, leaving the plastic sheath to allow drainage of the fluid. The fluid is drained by gravity, a syringe, or by connection to a vacuum bottle. Several litres of fluid may be drained during the procedure; however, if more than two litres are to be drained, it will usually be done over the course of several treatments. After the desired level of drainage is complete, the plastic sheath is removed and the puncture site bandaged. However, for every end-point investigated, while albumin was favorable as compared to other agents (e.g., plasma expanders, vasoconstrictors), these were not statistically significant and the meta-analysis was limited by the quality of the studies—two of which that were in fact unsuitable—included in it.
Complications
Paracentesis is known to be a safe procedure when ascitic fluid is readily visible, so complications are typically rare. Possible complications following or during the procedure involve infection, bleeding, the leakage ascitic of fluid, or bowel perforation.
The z-tracking technique has held particular importance in performing paracentesis. A z-track is a technique that allows for decreased ascitic fluid leak following the paracentesis by displacing the needle tracks with respect to the epidermis and the peritoneum.
thumb|296x296px|Ascitic fluid, 7 litres, drained during paracentesis
The ascitic white blood cell count can help determine if the ascites is infected. A count of 250 neutrophils per ml or higher is considered diagnostic for spontaneous bacterial peritonitis. Cultures of the fluid can be taken, but the yield is approximately 40% (72–90% if blood culture bottles are used). Empiric antibiotics are typically started when spontaneous bacterial peritonitis is highly suspected. A third-generation cephalosporin is typically started in these cases to cover the most common organisms, E. coli and Klebsiella, in SBP. The risk of bleeding may be increased if:
- prothrombin time > 21 seconds
- international normalized ratio > 1.6
- platelet count < 50,000 per cubic millimeter.
Absolute contraindication is the acute abdomen that requires surgery.
Relative contraindications are: