Paracentesis is a procedure to remove fluid that has accumulated in the abdominal cavity (peritoneal fluid), a condition called ascites . Ascites may be caused by infection, inflammation, abdominal injury, or other conditions, such as cirrhosis or cancer. The fluid is removed using a needle inserted through the abdominal wall and sent to a lab for analysis to determine the cause of the fluid buildup. Paracentesis also may be done to drain the fluid as a comfort measure in people with cancer or chronic cirrhosis.

The peritoneum is the lining of the abdominal cavity. It supports the organs in the abdomen and helps protect them from infection. The inside surface of the peritoneum produces a very small amount of peritoneal fluid that allows the organs in the abdomen to slide against the peritoneum and each other.

Paracentesis may be done to:

• Determine the cause of fluid buildup in the abdominal cavity (ascites).
• Diagnose infection in the peritoneal fluid.
• Detect certain types of cancer, such as liver cancer.
• Remove a large amount of fluid that is causing pain or difficulty breathing or that is affecting the function of the kidneys or the intestines (bowel).
• Evaluate abdominal injury.

This procedure may be done in your doctor's office, an emergency room, the X-ray department of a hospital, or at your bedside in the hospital.

If a large amount of fluid is going to be removed during the procedure, you may lie on your back with your head slightly raised. People who have less fluid removed may be allowed to sit up. The site where your doctor will insert the needle is cleaned with an antiseptic solution and draped with sterile towels.

Your doctor injects a local anesthetic into your abdominal wall to numb the area where the paracentesis needle will be inserted. Once the area is numb, your doctor will gradually insert the paracentesis needle where the fluid is likely to be. If your test is done in the X-ray department, an ultrasound may be used to confirm the location of fluid in your abdomen.

As the paracentesis needle is gradually advanced through the abdominal wall, your doctor will pull back on the syringe to ensure that neither a blood vessel nor the intestine has been punctured. When the abdominal cavity is entered, fluid will flow into the syringe. If a large amount of fluid is present, the paracentesis needle may be connected by a small tube to a vacuum bottle; fluid will then be drained through the needle into the vacuum bottle.

Generally, up to 4 L(1.1 gal) of fluid is removed. If your doctor needs to remove a larger amount of fluid, intravenous line (IV) fluids may be given through a vein in your arm to prevent low blood pressure or shock. It is important that you remain completely still throughout the procedure, unless you are asked to change positions to help move the fluid.

Once the desired amount of fluid has been removed, the needle is withdrawn and a bandage is placed over the puncture site. After the test, your pulse, blood pressure, and temperature are usually monitored. You may be weighed and the distance around your abdomen may be measured before and after the test.

This procedure usually takes about 20 to 30 minutes. It will take longer if a large amount of fluid is being removed. When it is over, you may resume normal activities unless your doctor tells you otherwise.

You may feel a brief, sharp stinging or burning pain when the local anesthetic is injected. When the paracentesis needle is inserted into the abdominal wall, you may again feel a temporary sharp pain or pressure, similar to having your blood drawn.

You may feel dizzy or lightheaded if a large amount of fluid is withdrawn. Tell your doctor if you do not feel well during the test.

After the procedure, you may notice some clear fluid draining from the needle site, especially if a large amount of fluid was removed from your abdominal cavity. The drainage should subside within 1 to 2 days. A small gauze pad covered by a bandage generally helps absorb the fluid. Ask your doctor how much drainage to expect.

There is a very slight chance that the needle used to withdraw the fluid might puncture the bladder, bowel, or a blood vessel within the abdomen.

If cancer cells are present in the peritoneal fluid, there is a slight risk that the needle used to withdraw the fluid might spread the cancer cells within the abdominal cavity.

If a large amount of fluid is removed, there is a small risk that your blood pressure could drop to a low level, leading to shock. If this occurs, intravenous (IV) fluids or medications, or both, may be given to help return your blood pressure to normal. There is also a small risk that the removal of fluid may decrease your kidney function. If this is a concern, IV fluids may be given during the paracentesis.

Contact your doctor immediately if you experience:

• A fever higher than 100 °F(37.8 °C).
• Severe abdominal pain.
• Increasing abdominal redness or tenderness.
• Blood in your urine.
• Bleeding or excessive drainage from the site where the paracentesis needle was inserted.

Paracentesis is a procedure to remove excess fluid that has accumulated in the abdominal cavity (peritoneal fluid), a condition called ascites. Fluid removed from your abdomen will be sent to a lab to be examined under a microscope. Preliminary results will be available within a few hours.

Thoracentesis is a procedure to remove fluid from the space between the lungs and the chest wall called the pleural space. It is done with a needle (and sometimes a plastic catheter) inserted through the chest wall. This pleural fluid may be sent to a lab to determine what may be causing the fluid to accumulate in the pleural space.

Normally only a small amount of pleural fluid is present in the pleural space. Accumulation of excess pleural fluid (pleural effusion) may be caused by many conditions, such as infection, inflammation, heart failure, or cancer. If a large amount of fluid is present, it may be difficult to breathe. Fluid inside the pleural space may be found during a physical examination and is usually confirmed by a chest X-ray.

Thoracentesis may be done to:

• Determine the cause of excess pleural fluid (pleural effusion).
• Relieve shortness of breath and pain caused by a pleural effusion.

This procedure may be done in your doctor's office, in the X-ray department of a hospital, in an emergency room, or at your bedside in the hospital. Your doctor may have a nurse assist with the procedure.

You will need to take off all or most of your clothes (you may be allowed to keep on your underwear if it does not interfere with the procedure). You will be given a cloth or paper covering to use during the procedure. During the procedure, you will be seated but leaning forward on a padded bedside table. If your test is done in the X-ray department, X-rays or an ultrasound may be used to confirm the location of fluid in your chest.

The needle site between your ribs will be cleaned with an antiseptic solution. Your doctor will give you a local anesthetic in your chest wall so you won't feel any pain when the longer needle that withdraws the fluid is inserted. Once the area is numb, your doctor will insert the needle to where the fluid has collected (pleural space). You may feel some mild pain or pressure as the needle enters the pleural space.

A syringe or a small tube attached to a vacuum bottle is used to remove the pleural fluid. Your doctor collects 50 mL(2 fl oz) to 100 mL(3 fl oz) of fluid at a time to send to the lab. Up to 1500 mL(51 fl oz) may be removed if the fluid is making it difficult for you to breathe. Once the fluid is removed, then the needle or small tube is removed and a bandage is put on the site.

An X-ray is usually taken right after the procedure to make sure that no complications have occurred. If more pleural fluid collects and needs to be removed, another thoracentesis may be done later.

This procedure takes about 10 to 15 minutes.

When you are given the shot to numb your skin at the needle site, you will feel a sharp stinging or burning sensation that lasts a few seconds. When the needle is inserted into the chest wall, you may again feel a sharp pain for a few seconds.

When the pleural fluid is removed, you may feel a sense of “pulling” or pressure in your chest. Tell your doctor or nurse if you feel faint or if you have any shortness of breath, chest pain, or uncontrollable cough.

If a large amount of pleural fluid was removed during the procedure, you will probably be able to breathe more easily.

Thoracentesis is generally a safe procedure. A chest X-ray is usually done right after the procedure to make sure that no complications have occurred. Complications may include:

• A partial collapse of the lung (pneumothorax). This may occur if the needle used to remove the pleural fluid punctures the lung, allowing air to flow into the pleural space.
• Pulmonary edema, which may occur if a large amount of fluid is removed.
• Infection and bleeding.
• Damage to the liver or spleen, though this is rare.

Thoracentesis is a procedure to remove fluid from the space between the lungs and the chest wall called the pleural space. Results from a lab are usually available in 1 to 2 days. If the fluid is being tested for an infection, such as tuberculosis, results may not be available for several weeks.