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Paracentesis is a procedure in which fluid is removed from the peritoneum for diagnostic and/or therapeutic purposes. Diagnostic paracentesis is the removal of a small volume of intraperitoneal fluid for the evaluation of newly diagnosed ascites or to assess for spontaneous bacterial peritonitis in patients with chronic ascites. Therapeutic paracentesis is the removal of large volumes of intraperitoneal fluid to relieve associated abdominal pain and/or respiratory symptoms. Relative contraindications include pregnancy, visceral distention, severe coagulopathy, and infection over the procedure site. The procedure is always performed using sterile technique and is usually guided by ultrasound. Complications include a persistent fluid leak, postparacentesis circulatory dysfunction, and hepatic encephalopathy.
- Diagnostic paracentesis: aspiration of a small volume of fluid from the peritoneum to aid in the diagnosis and management of ascites and other intraabdominal conditions
- Therapeutic paracentesis: removal of a large volume of fluid from the peritoneum to relieve symptoms caused by ascites
- Large volume paracentesis: removal of > 5 L of fluid from the peritoneum during one procedure 
Diagnostic paracentesis 
- New-onset ascites
- Suspected spontaneous bacterial peritonitis (SBP): See “Indications for diagnostic paracentesis in SBP” for details.
Therapeutic paracentesis 
- Absolute: none 
- Relative 
We list the most important contraindications. The selection is not exhaustive.
Landmarks and positioning
- Lower quadrant: RLQ or LLQ
- Large volume ascites: The patient is supine with the head of the bed elevated.
- Small volume ascites
Ultrasound guidance 
Recommended because it can locate fluid collections, inform patient positioning, and identify conditions that increase procedural risk
- Use color flow Doppler to identify avoidable blood vessels in the abdominal wall.
- Static guidance (most common): Optimal needle entry site is identified and marked prior to skin prep.
- Dynamic guidance: real-time ultrasound guidance of needle movements, e.g., for small volumes of fluid and/or enlarged viscera
- See “FAST” for the basic principles of abdominal ultrasound.
Consider performing paracentesis under ultrasound guidance to reduce the risk of serious complications and improve success rates. 
All patients 
- Ultrasound machine
- Sterile ultrasound probe cover
- Sterile gown and gloves
- Sterile gauze
- Sterile drapes
- Surgical mask
- Antiseptic solution
- Occlusive dressing
- Local anesthetic
- 5 mL syringe
- 18-gauge needle for drawing up
- 25-gauge needle for administration
Diagnostic paracentesis 
- 20–22-gauge 1.5 inch needle
- 18–22-gauge 3.5 inch spinal needle for obese patients
- 60 mL syringe for sample collection
- Blood culture bottles
Therapeutic paracentesis 
- Prepackaged set, e.g., 18-gauge needle with preloaded 8 Fr catheter
- Or 14–18-gauge peripheral IV catheter 
Drainage set-up (if indicated)
- High-pressure tubing
- Drainage bag or evacuated container
- Ensure the patient has voided.
- Ready the ultrasound machine.
- Perform abdominal ultrasound.
- Determine optimal patient position and entry site.
- Measure the depth between soft tissue and fluid.
- Mark the proposed entry site and ensure the patient remains in this position.
- Perform skin preparation and maintain a sterile field.
- Assemble the appropriate needle, stopcock, and syringe.
- peritoneum to include the
- Consider cardiac monitoring.
- Pull the skin ∼ 2 cm caudad prior to needle insertion ( ).
- Insert the needle perpendicular to the skin at the marked location.
- Apply negative pressure on the syringe plunger and advance slowly until fluid returns.
- Advance another few millimeters, then fix the needle in this location or slide the catheter off the needle.
- Diagnostic paracentesis: Aspirate 60 mL of fluid into large syringes.
- Therapeutic paracentesis: Connect high-pressure tubing from the needle to the drainage system.
- Large volume paracentesis: Infuse albumin during or immediately after the procedure. 
- Once fluid collection is complete, remove the needle or catheter.
- Apply an occlusive dressing.
Pitfalls and troubleshooting
The following can be prevented by using real-time ultrasound guidance and needle-catheter systems with side ports (e.g., Caldwell needle) to improve flow.
Interruption of fluid flow 
- Cause: obstruction likely, e.g. kinked catheter, orifice obstructed by omentum or other intraabdominal structure
- Management: inject a small amount of intraperitoneal fluid back through the needle or catheter, then reattempt aspiration.
No fluid flow 
- Small volume of fluid or loculated fluid, or obstruction
Postprocedural fluid leak 
- Prevention: Z-track technique
- Management 
Postparacentesis circulatory dysfunction (PPCD) 
- Clinical presentation: AKI, hyponatremia, hepatic encephalopathy, and/or clinical deterioration occurring hours to days after paracentesis
- Prevention: administration of albumin at the time of large volume paracentesis 
- Systemic: hepatic encephalopathy, hyponatremia
- Local: abdominal wall hematoma
- Intraperitoneal (rare): visceral injury, intraperitoneal hemorrhage
We list the most important complications. The selection is not exhaustive.