Abdominal paracentesis

Abdominal paracentesis, more commonly referred to as an ascitic tap, is a procedure that can be performed to collect peritoneal fluid for analysis or as a therapeutic intervention.

Indications

• diagnostic: especially for newly diagnosed-diagnosed ascites
  • determine aetiology of ascites
  • assess for bacterial peritonitis
• therapeutic
  • to relieve pressure effects of ascites, including respiratory compromise

Contraindications

• relative ⁴
  • coagulopathy (INR >2.0)
  • severe thrombocytopenia (platelet count <50 x 10³/microL/μL)
  • infection of the overlying skin
  • pregnancy

Procedure

Prior to procedure being performed assessment of the amount and nature of the ascites should be made using preferably CT or ultrasound. The patient's coagulation profile should be considered and informed consent obtained. The indication for the procedure should be considered to determine the volume of fluid to be removed.

Full aseptic technique, with antiseptic skin preparation and infiltration of local anaesthetic should be employed. Patient can be positioned to allow accumulation of fluid to one side.

Procedure can be performed blind using the landmark technique (15 cm lateral to the umbilicus in the right or left lower quadrant) or after ultrasound marking prior to procedure. It can also be done image-guided, almost always with ultrasound ¹.

An 18G needle with a 10 mL syringe is passed using a Z-track technique, to minimise the risk of persistent leak following removal. Back pressure is kept on the syringe until ascitic fluid is aspirated.

The Seldinger technique can be used to leave an ~8 Fr catheter in situfor therapeutic procedures. Alternatively a trocar catheter set can also be used. 

Fluid can be sent for the following tests:

• Gram stain, culture and sensitivity
• cell count (especially neutrophils)
• cytology
• albumin levels (to assess serum ascites albumin gradient (SA-AG)
• triglyceride level (high in chylous ascites)
• glucose level
• lactate dehydrogenase level
• amylase level (suggests pancreatic pathology)

Postprocedure care should be taken with therapeutic procedures to avoid large fluid shifts. Albumin needs to be replaced parenterally to avoid disequilibrium, in recognition of the risk of post paracentesis circulatory collapse. Diuretics, salt and water restriction are frequently used.

Complications

• persistent leak (can be collected in stoma bag until heals, minimised with Z-track technique) ¹
• circulatory collapse (minimised by replacing volume and albumin) ²
• bleeding (locally or intraperitoneal)
• localised infection
• bowel perforation