Paracentesis 

Updated: Jul 05, 2018
Author: Gil Z Shlamovitz, MD, FACEP; Chief Editor: Vikram Kate, MBBS, MS, PhD, FRCS, FACS, FACG, FRCS(Edin), FRCS(Glasg), FIMSA, MAMS, MASCRS 

Overview

Background

Paracentesis is a procedure in which a needle or catheter is inserted into the peritoneal cavity to obtain ascitic fluid for diagnostic or therapeutic purposes.[1, 2] Ascitic fluid may be used to help determine the etiology of ascites, as well as to evaluate for infection or presence of cancer. With regard to differentiation of transudate from exudate, the preferred means for characterizing ascites is the serum-ascitic albumin gradient (SAAG).[3]

The SAAG is calculated by subtracting the albumin concentration of the ascitic fluid from the albumin concentration of a serum specimen obtained on the same day. The SAAG correlates directly with portal pressure. Transudative ascites occurs when a patient's SAAG level is greater than or equal to 1.1 g/dL (portal hypertension). Exudative ascites occurs when patients have SAAG levels lower than 1.1 g/dL. (See the Ascites Albumin Gradient calculator.)

Causes of transudative ascites include the following:

Causes of exudative ascites include the following:

An alternative way of differentiating ascites due to portal hypertension from that due to other causes is to measure ascitic fluid viscosity with a cutoff of 1.65.[4] Ascitic fluid viscosity has also been demonstrated to predict renal impairment in hepatic patients at a cutoff of 1.35 and a long intensive care unit (ICU) stay at a cutoff of 1.995.

A newer noninvasive method of differentiating exudative from transudative ascites by using B-mode gray-scale ultrasound histogram analysis has been described and appears to be effective.[5]  In this method, the ascites–to–rectus abdominis muscle echogenicity ratio (ARAER) is measured. A value higher than 0.002 is regarded as exudative ascites, whereas a value lower than 0.002 is regarded as transudative ascites.

In patients with malignant ascites related to ovarian cancer, an ascites symptom mini-scale has been developed that serves as a simple and easy tool for assessment.[6]  This scale includes five parameters: shortness of breath, distended abdomen, reduced mobility, fatigue, and loss of appetite. It can be used to identify patients with mild symptoms who may benefit from paracentesis.

Spontaneous bacterial peritonitis

Infection of ascitic fluid without intra-abdominal infection usually occurs in patients with chronic liver disease due to translocation of enteric bacteria. Common pathogens include Escherichia coli, Klebsiella pneumoniae, enterococcal species, and Streptococcus pneumoniae.[7] Patients with renal failure who use abdominal peritoneal dialysis are also at increased risk, as are children with nephrosis or systemic lupus erythematosus. Anaerobic bacteria are not associated with spontaneous bacterial peritonitis (SBP).

An ascitic fluid polymorphonuclear leukocyte (PMN) count higher than 250/μL (neutrocytic ascites), with the percentage of PMNs in the fluid usually greater than 50%, is presumptive evidence of SBP. Patients whose ascitic fluid meets these criteria should be treated empirically, regardless of symptoms. Secondary bacterial peritonitis is defined as infected ascitic fluid associated with an intra-abdominal infection.

A report by Lutz et al demonstrated that the relative PMN count, as compared with the absolute PMN count, is a less expensive marker associated with bacterascites and can be used to predict future episodes of SBP.[8]  This may be sueful for the purpsoes of risk stratification.

Indications

Diagnostic tap is used for the following:

  • New-onset ascites - Fluid evaluation helps to determine etiology, differentiate transudate versus exudate, detect the presence of cancerous cells, or address other considerations
  • Suspected spontaneous or secondary bacterial peritonitis
  • Refractory ascites [9]

Therapeutic tap is used for the following:

A report by Huang et al found that abdominal paracentesis drainage brought about clinical improvement in patients who had non-hypertriglyceridemia-induced severe acute pancreatitis with triglyceride elevation and pancreatitis-associated ascitic fluid.[10]

Large-volume paracentesis is often required in patients with refractory ascites. A report by Bureau et al described the use of a low-flow pump system that moves the fluid from the abdominal cavity into the bladder, from which it is removed via micturition.[11] This was shown to improve patients' quality of life and reduced the need for repeated large-volume paracentesis.

Contraindications

An acute abdomen that requires surgery is an absolute contraindication.

Severe thrombocytopenia (platelet count < 20 × 103/μL) and coagulopathy (international normalized ratio [INR] >2.0) are relative contraindications.

Patients with an INR greater than 2.0 should receive fresh frozen plasma (FFP) prior to the procedure. One strategy is to infuse one unit of fresh frozen plasma before the procedure and then perform the procedure while the second unit is infusing.

Patients with a platelet count lower than 20 × 103/μL should receive an infusion of platelets before the procedure.

In patients without clinical evidence of active bleeding, routine laboratory tests such as prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet counts may not be needed before the procedure.[12] In these patients, pretreatment with FFP, platelets, or both before paracentesis is also probably not needed.

A study of 608 patients (72% with alcohol-related liver disease) found a low overall rate of complications that required transfusions (0.2%) and a higher incidence of significant hemoglobin drop among those with severe renal failure (creatinine > 6 mg/dL).[12]

A prospective study of 171 patients undergoing paracentesis found that "major" complications occurred in 1.6% of procedures and included five episodes of bleeding and three infections, resulting in death in two cases. Major complications were associated with therapeutic but not diagnostic procedures and tended to be more prevalent in patients with low platelet counts (< 50 × 109/L), patients who were Child-Pugh stage C, and patients with alcoholic cirrhosis.[13]

Other relative contraindications include the following:

  • Pregnancy
  • Distended urinary bladder
  • Abdominal wall cellulitis
  • Distended bowel
  • Intra-abdominal adhesions

Technical Considerations

Best practices

Depending on the clinical situation, fluid may be sent for the following laboratory tests:

  • Gram stain - In a retrospective review of 796 peritoneal fluid samples, the evaluation of Gram stain results rarely provided clinically useful information for the detection of spontaneous bacterial peritonitis [14]
  • Cell count (elevated counts may suggest infection)
  • Bacterial culture
  • Total protein level
  • Triglyceride levels (elevated in chylous ascites)
  • Bilirubin level (may be elevated in bowel perforation)
  • Glucose level
  • Albumin level, used in conjunction with serum albumin levels obtained the same day (used to calculate SAAG; see the Ascites Albumin Gradient calculator)
  • Amylase level (elevation suggests pancreatic source)
  • Lactate dehydrogenase (LDH) level
  • Cytology

After proper antiseptic preparation and local anesthesia, a diagnostic tap can be performed with a 10- to 20-mL syringe and an 18-gauge needle.

After proper antiseptic preparation and local anesthesia, a therapeutic tap can be performed with an intravenous (IV) catheter over the needle connected to drainage tubing.

In patients who are afebrile, alert, and have no other signs of bacterial peritonitis, ascitic fluid labs are often not necessary to rule out SBP.[15, 16]

To minimize the risk of persistent leak from the puncture site, use a small-gauge needle or take a "Z" track during insertion of the needle. (During removal of the needle, the subcutaneous tissue seals on itself.)

In a retrospective review of 796 peritoneal fluid samples, the evaluation of Gram stain results rarely provided clinically useful information for the detection of SBP.[14]

Dietary sodium restriction and diuretics do not often provide symptomatic relief of refractory ascites in patients in advanced stages of cancer. Although paracentesis does effectively drain ascitic fluid, the condition invariably recurs, and repeated procedures are necessary. A 2008 study reported that a permanent peritoneal catheter to drain abdominal fluid greatly reduced the symptoms of ascites in these patients and avoided the costs and complications of frequent paracentesis procedures.[17]

A meta-analysis suggests that the use of albumin in cirrhotic patients undergoing paracentesis reduces paracentesis-induced circulatory dysfunction and reduces death and renal impairment.[18]

The ascites index, which is estimated with basic ultrasound equipment, is defined as the sum total of ascites extent in all four external quadrants of the abdomen. It appears to be a promising tool for estimating and monitoring ascites following paracentesis as reported in ovarian hyperstimulation syndrome.[19]

Complication prevention

In cases with a persistent leak, a single skin suture might solve the problem. The application of an ostomy bag around the puncture site keeps the leak contained until it is eventually sealed off.

Postparacentesis hypotension is a delayed complication that may occur more than 12 hours after a procedure in which large volumes are taken off. Patients can be pretreated with a colloid solution, such as albumin, to decrease the frequency of this complication, though no difference in survival has been noted relative to other plasma expanders.[20]

Timing of paracentesis

Whereas studies suggest that early paracentesis (< 12 hours from admission) improves short term survival of hospitalized patients with SBP in comparison with delayed paracentesis, it seems that earlier administration of appropriate antibiotics in the early paracentesis group might have been a major contributing factor.[21, 22]

At this time and in the absence of prospective, randomized, controlled data, the authors recommend early diagnostic or therapeutic paracentesis and early empiric antibiotic administration in patient suspected of having SBP. When it appears that large-volume paracentesis is likely to be required, the authors suggest consideration of early small-volume paracentesis (ultrasound, syringe, and needle technique) followed by delayed and planned large-volume paracentesis (during hospitalization) under appropriate monitoring and hemodynamic support to minimize the risk of circulatory dysfunction induced by large-volume paracentesis.

Ultrasound guidance

The process of peritoneal drainage can be carried out effectively and safely by employing a specific ultrasound-guided technique for the following[23] :

  • Confirm the presence of ascites
  • Quantify and qualify the ascites
  • Determine trajectory and depth
  • Avoid superficial blood vessels
  • Perform an ultrasound-assisted paracentesis
  • Perform an ultrasound-guided paracentesis
  • Check the position of the wire prior to dilating
 

Periprocedural Care

Patient Education and Consent

Explain the procedure, benefits, risks, complications, and alternative options to the patient or the patient's representative, and obtain signed informed consent.

Equipment

The equipment required can be found in a disposable paracentesis/thoracocentesis kit (see the image below).

Paracentesis/thoracocentesis tray. Paracentesis/thoracocentesis tray.

Equipment includes the following:

  • Antiseptic swab sticks
  • Fenestrated drape
  • Lidocaine 1%, 5-mL ampule
  • Syringe, 10 mL
  • Injection needles, 22-gauge (two)
  • Injection needle, 25-gauge
  • Scalpel, No. 11 blade
  • Catheter, 8 French, over 18-gauge × 7.5-in. needle with three-way stopcock, self-sealing valve, and a 5-mL Luer-Lok syringe
  • Syringe, 60 mL
  • Introducer needle, 20-gauge
  • Tubing set with roller clamp
  • Drainage bag or vacuum container
  • Specimen vials or collection bottles (three)
  • Gauze, 4 × 4 in.
  • Adhesive dressing

Patient Preparation

Anesthesia

Local anesthesia with injection of lidocaine is employed. (See Technique.) For more information, see Local Anesthetic Agents, Infiltrative Administration.

Positioning

Patients with severe ascites can be positioned supine. Patients with mild ascites may need to be positioned in the lateral decubitus position, with the skin entry site near the gurney. The lateral decubitus position is advantageous because air-filled loops of bowel tend to float in a distended abdominal cavity.

The two recommended areas of abdominal wall entry for paracentesis are as follows (see the image below):

  • 2 cm below the umbilicus in the midline (through the linea alba)
  • 5 cm superior and medial to the anterior superior iliac spines on either side
Paracentesis: standard sites. Paracentesis: standard sites.

The authors recommend the routine use of ultrasonography to verify the presence of a fluid pocket under the selected entry site in order to increase the rate of success (see image below).[24]

Ultrasonogram showing ascites. Ultrasonogram showing ascites.

The use of ultrasonography also helps the practitioner avoid a distended urinary bladder or small bowel adhesions below the selected entry point. To minimize complications, avoid areas of prominent veins (caput medusae), infected skin, or scar tissue.

 

Technique

Aspiration of Ascitic Fluid From Peritoneal Cavity

The video below depicts ultrasound-assisted large-volume paracentesis. The description that follows outlines the steps in the procedure.

Ultrasound-assisted large-volume paracentesis. Video courtesy of George Y Wu, MD, PhD.

Ensure that the patient's bladder is empty, either through voluntary emptying on the part of the patient or through the use of a Foley catheter.

Position the patient, and prepare the skin around the entry site with an antiseptic solution (see the first image below). Apply a sterile fenestrated drape to create a sterile field (see the second image below).

Paracentesis. Application of antiseptic solution. Paracentesis. Application of antiseptic solution.
Paracentesis. Draping. Paracentesis. Draping.

Use the 5-mL syringe and the 25-gauge needle to raise a small lidocaine skin wheal around the skin entry site (see the image below).

Paracentesis. Local anesthesia: skin wheal. Paracentesis. Local anesthesia: skin wheal.

Switch to the longer 20-gauge needle, and administer 4-5 mL of lidocaine along the catheter insertion tract (see the image below). Make sure to anesthetize all the way down to the peritoneum. The authors recommend alternating injection and intermittent aspiration down the tract until ascitic fluid is noticed in the syringe. Note the depth at which the peritoneum is entered. In obese patients, reaching the peritoneum may involve passing through a significant amount of adipose tissue.

Paracentesis. Local anesthesia: deeper injection. Paracentesis. Local anesthesia: deeper injection.

Use the No. 11 scalpel blade to make a small nick in the skin to allow easier passage of the catheter (see the image below).

Paracentesis. Skin nick for passage of catheter. Paracentesis. Skin nick for passage of catheter.

Insert the needle directly perpendicular to the selected skin entry point (see the image below). Slow insertion in increments of 5 mm is preferred to minimize the risk of inadvertent vascular entry or puncture of the small bowel.

Paracentesis. Insertion of needle into selected sk Paracentesis. Insertion of needle into selected skin entry point.

Continuously apply negative pressure to the syringe as the needle is advanced. Upon entry into the peritoneal cavity, loss of resistance is felt, and ascitic fluid can be seen filling the syringe (see the image below). At this point, advance the device 2-5 mm into the peritoneal cavity to prevent misplacement during catheter advancement. In general, avoid advancing the needle deeper than the safety mark present on most commercially available catheters or deeper than 1 cm beyond the depth at which ascitic fluid was noticed in the lidocaine syringe.

Paracentesis. Filling of syringe with ascitic flui Paracentesis. Filling of syringe with ascitic fluid upon peritoneal entry.

Use one hand to firmly anchor the needle and syringe securely in place to prevent the needle from entering further into the peritoneal cavity (see the image below).

Paracentesis. Stabilization of needle and syringe. Paracentesis. Stabilization of needle and syringe.

Use the other hand to hold the stopcock and catheter and advance the catheter over the needle and into the peritoneal cavity all the way to the skin (see the image and video below). If any resistance is noticed, the catheter was probably misplaced into the subcutaneous tissue. If this is the case, withdraw the device completely and reattempt insertion. When withdrawing the device, always remove the needle and catheter together as a unit in order to prevent the bevel from cutting the catheter.

Paracentesis. Advancing catheter over needle. Paracentesis. Advancing catheter over needle.
Paracentesis. Advancement of catheter over needle.

While holding the stopcock, pull the needle out. The self-sealing valve prevents fluid leak.

Attach the 60-mL syringe to the three-way stopcock and aspirate to obtain ascitic fluid, and distribute it to the specimen vials (see the images and video below). Use the three-way valve as needed to control fluid flow and prevent leakage when no syringe or tubing is attached.

Paracentesis. Sample collection. Paracentesis. Sample collection.
Paracentesis. Sample collection.
Peritoneal fluid in vials. Peritoneal fluid in vials.

Connect one end of the fluid collection tubing to the stopcock and the other end to a vacuum bottle or a drainage bag (see the images below).

Paracentesis. Connection of collecting tube. Paracentesis. Connection of collecting tube.
Paracentesis. Drainage of ascitic fluid into vacuu Paracentesis. Drainage of ascitic fluid into vacuum bottle.

A study by Kelil et al demonstrated that the use of wall suction and plastic canisters to drain and collect fluid during image-guided therapeutic paracenteses was a safe alternative to the use of evacuated glass bottles and reduced per-procedure costs.[25]

 The catheter can become occluded by a loop of bowel or omentum. If the flow stops, kink or clasp the tubing to avert loss of suction, then break the seal and manipulate the catheter slightly, and finally reconnect and see if flow resumes. Rotating the catheter about the long axis can sometimes reinstitute flow in models with side ports.

After the desired amount of ascitic fluid has been drained, remove the catheter (see the image below). Apply firm pressure to stop bleeding, if present. Place a bandage over the skin puncture site.

Paracentesis. Catheter removal. Paracentesis. Catheter removal.

Complications

Complications from paracentesis may include the following:

  • Failed attempt to collect peritoneal fluid
  • Persistent leak from the puncture site
  • Wound infection
  • Abdominal wall hematoma
  • Spontaneous hemoperitoneum - This rare complication is due to mesenteric variceal bleeding after removal of a large amount of ascitic fluid (>4 L).
  • Hollow viscus perforation (small or large bowel, stomach, bladder)
  • Catheter laceration and loss in abdominal cavity
  • Laceration of major blood vessel (aorta, mesenteric artery, iliac artery)
  • Postparacentesis hypotension
  • Dilutional hyponatremia
  • Hepatorenal syndrome [26]

A prospective study of 171 patients undergoing paracentesis found that "major" complications occurred in 1.6% of procedures and included five episodes of bleeding and three infections, resulting in death in two cases. Major complications were associated with therapeutic but not diagnostic procedures and tended to be more prevalent in patients with low platelet counts (< 50 × 109/L), patients who were Child-Pugh stage C, and patients with alcoholic cirrhosis.[13]

 

Questions & Answers

Overview

What is paracentesis?

How is serum-ascitic albumin gradient (SAAG) used to differentiate ascites in paracentesis results?

What are the possible etiologies of transudative ascites?

What are the possible etiologies of exudative ascites?

How are different types of ascites differentiated in paracentesis results?

Which patients are at increased risk for infection of ascitic fluid without intra-abdominal infection?

How is spontaneous bacterial peritonitis (SBP) diagnosed following paracentesis?

What are the indications for diagnostic paracentesis?

What are the indications for a therapeutic paracentesis?

When is abdominal paracentesis drainage indicated?

What is the indication for a large-volume paracentesis?

What are the contraindications for paracentesis?

When is fresh frozen plasma (FFP) indicated prior to paracentesis?

When is platelet infusion indicated prior to paracentesis?

Which lab testing is indicated prior to paracentesis?

What is the overall complication rate of paracentesis?

Which lab tests are performed in the evaluation of fluid from paracentesis?

How is a diagnostic paracentesis tap performed?

How is a therapeutic paracentesis tap performed?

Which clinical signs can be used to rule out SBP?

How is risk of puncture site persistent leaks minimized in paracentesis?

Are Gram stain results effective for detecting SBP following paracentesis?

What is the role of the ascites index in the evaluation of patients who've had a paracentesis ?

Is paracentesis effective for symptomatic relief of refractory ascites in advanced stages of cancer?

Can albumin reduce adverse effects of paracentesis in patients with cirrhosis?

How is a persistent leak following paracentesis treated?

When is postparacentesis hypotension and how is it prevented?

What is the optimal timing of paracentesis in patients with suspected SBP?

What are the benefits of ultrasound guidance in performing a paracentesis?

Periprocedural Care

What education about paracentesis should a patient receive prior to giving informed consent?

What equipment is used in paracentesis?

How is local anesthesia used in paracentesis?

How should patients be positioned for paracentesis?

What are the possible abdominal wall entries for paracentesis?

What is the role of ultrasonography in paracentesis?

Technique

How is an ultrasound-assisted paracentesis performed?

How is ascitic fluid aspirated from the peritoneal cavity during paracentesis?

Is there an effective alternative to the use of evacuated glass bottles in paracentesis?

How is occlusion in the catheter corrected during paracentesis?

What are possible complications of paracentesis?

What is the major complication rate of paracentesis?