Paracentesis vs Thoracentesis: When To Use Each Procedure

Paracentesis vs Thoracentesis If patients’ lymphatic systems aren’t working efficiently, they can experience water retention (edema) in various parts of their bodies. Edema commonly occurs when patients have an infection, kidney disease, venous insufficiency, heart failure, or cirrhosis of the liver.

This abnormal accumulation of fluid can be drained through minimally invasive treatments using a local anesthetic. Learn the difference between paracentesis and thoracentesis to understand when to use each. 

Paracentesis vs Thoracentesis: Use Cases and Risks

To determine which of the two procedures should be administered, note the area of the body where the fluid accumulates. Use paracentesis if the excess fluid is in the abdominal cavity (ascites). If it’s in the pleural cavity or the space between the lungs and the chest wall, perform a thoracentesis. 

Both can be diagnostic or therapeutic based on the extent of fluid retention. 

Ascites and Paracentesis

Ascites refers to fluid buildup in the peritoneal cavity, which can affect your lungs, kidneys, and other organs. It develops in 60,000 out of 100,000 patients with cirrhosis. Since it marks the transition to decompensated cirrhosis, steps must be taken to minimize ascitic fluid volume without causing a reduction in intravascular volume.

Once the volume of ascites is quantified, a paracentesis procedure (with albumin) can relieve patients with tense ascites or hepatic hydrothorax. It’s important to consider the patient’s drug history pre-procedure for anticoagulant reversal as a pre-operative international normalized ratio (INR) is not indicative of coagulation. Having said this, paracentesis can be safely performed in emergencies with minimal risk of major bleeding even in the presence of full anticoagulation without reversing the anticoagulant. A specimen volume of ≥80 mL can improve cytologic sensitivity for malignant ascites.

Since many health conditions can cause ascites, it’s recommended that clinicians perform ascitic fluid analysis in the differential diagnosis of ascites. If it developed due to cardiac failure, they may need to go in with serum (blood) brain natriuretic peptide in an ethylenediaminetetraacetic acid (EDTA) tube to induce vasodilatation, increase diuresis, and inhibit renin and aldosterone production.


While it’s an outpatient procedure, the fluid should be drained as rapidly as possible to keep protein losses and the risk of secondary infection low. Watch for spontaneous bacterial peritonitis—an acute infection without a source or symptoms. Known to occur in 10% to 30% of patients, it can be life-threatening if it isn’t promptly addressed.

Bleeding is another dreaded complication, often affecting those with severe liver disease. The outcome is poor, resulting in 30-day mortality among 42.6% of patients. if it occurs but the frequency of major bleeding with a ultrasound-guided paracentesis is very low (~0.25%) and can be reduced to about 0.1% if a two-probe technique is used for paracentesis.

Other common concerns include ascitic fluid leakage, infection, and bowel perforation. These risks can be reduced with ultrasound guidance since it can help prevent the puncturing of major vessels in those with mild to moderate ascites

Pleural Effusion and Thoracentesis 

The pleural space maintains negative pressure, acting as a suction that keeps the lungs from collapsing. So, when air and fluid accumulate inside the cavity, it can lead to chest pain, respiratory distress, and hemodynamic compromise.

These can be treated with thoracentesis. Whether the treatment will be diagnostic or therapeutic in nature will depend on the type of pleural effusion, specifically if it’s exudative or transudative. 

If the etiology is unclear, a fluid sample of 20cc to 30cc can be sent for analysis. This will help you verify whether there’s a new infection or a decompensated chronic condition. If the patient has an overlying cutaneous infection, coagulopathy, thrombocytopenia, pleurodesis, or pleural adhesions at the site of entry, medical practitioners should proceed with caution. An ultrasound-guided thoracentesis can be safely performed with a platelet count of 20,000 or higher and can be performed under full anticoagulation without reversal in emergency situations.

It’s also vital to ensure proper post-care to avoid complications like pneumothorax which can increase the risk of congestive heart failure.


Post thoracentesis, the possibility of the re-expansion of pulmonary edema is low. For decades, it’s been known to affect 0% to 1% of patients. Should it occur, it is  generally mild and has a mortality rate of 20%

Symptoms include chest discomfort, a persistent but severe cough, the production of frothy sputum, and dyspnea at rest. 

Treatment is based on the severity of the condition which is diagnosed with a chest radiographic x-ray. This diagnostic procedure can help determine whether oxygen supplementation or noninvasive/invasive ventilation is required to ensure a successful outcome.

Minimizing Iatrogenic Hemorrhage

If iatrogenic hemorrhage (bleeding) occurs following a diagnostic or therapeutic paracentesis or thoracentesis treatment, supportive transfusions should be administered and then consult interventional radiology or CT surgery to control the bleeding. This can be accomplished with transcatheter coiling and embolization which are associated with better outcomes.

Paracentesis vs Thoracentesis Positioning

For paracentesis, a supine position with the head of the bed slightly elevated (anywhere between 45 to 90 degrees) or a lateral decubitus position is advised.

For thoracentesis, a seated position with the patient leaning slightly forward is prescribed.

Safely Administer Paracentesis and Thoracentesis With Hospital Procedures Consultants

Used for diagnosis and treatment, paracentesis and thoracentesis are two vital procedures that every medical professional needs to learn. Aside from administering them safely and effectively, practitioners must know when to use them, their associated risks, and the tools used such as tray custom paracentesis vs thoracentesis ultrasound.

To more thoroughly understand paracentesis and thoracentesis, Hospital Procedures Consultants offers courses that can help you become familiar with these two procedures. 

Our paracentesis training is part of our Hospitalist and Emergency Procedures CME course where we teach 20 of the most essential procedures that are used in ICU, ER, and hospital wards.

Meanwhile, our thoracentesis training teaches clinicians how to perform thoracentesis using a landmark-guided technique or ultrasound. It also helps participants learn about potential complications and how to examine pleural fluid.

You can learn more about them through our web pages on the paracentesis course and the thoracentesis course.


Prado, V. Chein, S. Reinoso, JL. Sanjay, A. Shashvat, P. Smith, S. Risk of Re-Expansion Pulmonary Edema Following Large-Volumethoracentesis. Chest Annual Meeting. 2020/10
Kasmani, R. Irani, F. Okoli, K. Mahajan, V. Re-expansion pulmonary edema following thoracentesis. CMAJ. 2010 Dec 14; 182(18)
Harvey, J. Prentice, R. George, J. Diagnostic and therapeutic abdominal paracentesis. Med J Aust. 2023 Jan; 218(1): 18–21.
Chandel, K. Rana, S. Patel, R. Tripathy, T. Mukun, A. Bedside USG-Guided Paracentesis – A Technical Note for Beginners J Med Ultrasound. 2022 Jul-Sep; 30(3): 215–216

Read all articles in Featured, Paracentesis, Thoracentesis
Tags: thoracentesis vs paracentesis position, tray custom paracentesis vs thoracentesis ultrasound

Live Courses

Online Courses

Get Live & Online Courses Info

Please send me information on Live and Online Courses

* indicates required