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]

Characterization of ascitesAscitic fluid may be used to help determine its etiology as well as to evaluate for infection or presence of cancer. With regard to differentiation of transudate from exudates, 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 less than 1.1 g/dL. See the Ascites Albumin Gradientcalculator.

Causes of ascitesCauses of transudative ascites include the following:

Hepatic cirrhosis Alcoholic hepatitis Heart failure Fulminant hepatic failure Portal vein thrombosis

Causes of exudative ascites include the following:

Peritoneal carcinomatosis Inflammation of the pancreas or biliary system Nephrotic syndrome Peritonitis Ischemic or obstructed bowel

Spontaneous bacterial peritonitisInfection 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.[4] Patients with renal failure who use abdominal peritoneal dialysis are also at increased risk, as are children with nephrosis orsystemic lupus erythematosus. Anaerobic bacteria are not associated withspontaneous bacterial peritonitis (SBP).

An ascitic fluid polymorphonuclear (PMN) count of more than 250 cells/μL (neutrocytic ascites), with the percentage of PMNs in the fluid usually greater than 50%, is presumptive evidence of SBP. Patients whose level 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.

IndicationsDiagnostic 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 peritonitisTherapeutic tap is used for the following:

Respiratory compromise secondary to ascites Abdominal pain or pressure secondary to ascites (including abdominal compartment syndrome)

ContraindicationsAn acute abdomen that requires surgery is an absolute contraindication.

Severe thrombocytopenia (platelet count < 20 X 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 platelet count of less than 20 X 103/μL should receive an infusion of platelets prior to performing 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 prior to the procedure.[5] In these patients, pretreatment with FFP, platelets, or both before the 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).[5]

A prospective study of 171 patients undergoing paracentesis found that "major" complications occurred in 1.6% of procedures and included 5 episodes of bleeding and 3 infections, resulting in death in 2 cases. Major complications were associated with therapeutic but not diagnostic procedures and tended to be more prevalent in patients with low platelet counts (< 50 X 10(9)/L), patients who were Child-Pugh stage C, and patients with alcoholic cirrhosis.[6]

Other relative contraindications include the following:

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

EquipmentThe equipment required can be found in a disposable paracentesis/thoracentesis kit (see image below).

Paracentesis/thoracentesis tray.

Equipment includes the following:

Antiseptic swab sticks Fenestrated drape Lidocaine 1%, 5-mL ampule Syringe, 10 mL Injection needles, 22 gauge (ga), 2 Injection needle, 25 ga

Scalpel, no. 11 blade Catheter, 8F, over 18 ga × 7 1/2" needle with 3-way stopcock, self-sealing valve, and a 5-mL

Luer-Lock syringe Syringe, 60 mL Introducer needle, 20 ga Tubing set with roller clamp Drainage bag or vacuum container Specimen vials or collection bottles, 3 Gauze, 4 × 4 inch Adhesive dressing

PositioningThe two recommended areas of abdominal wall entry for paracentesis are as follows (see 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 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). [7]

Ultrasound ascites.

The ultrasound 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 medusa), infected skin, or scar tissue.

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.

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

Empty the patient's bladder, either voluntarily or with a Foley catheter.

Position the patient and prepare the skin around the entry site with an antiseptic solution (see image below).

Application of antiseptic solution.

Apply a sterile fenestrated drape to create a sterile field (see image below).

Draping.

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

Local anesthesia - skin wheal.

Switch to the longer 20-ga needle and administer 4-5 mL of lidocaine along the catheter insertion tract (see 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.

Local anesthesia - deeper injection.

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

Skin nick.

Insert the needle directly perpendicular to the selected skin entry point (see 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.

Insertion of needle into selected skin entry point.

Continuously apply negative pressure to the syringe as the needle is advanced. Upon entry to the peritoneal cavity, loss of resistance is felt and ascitic fluid can be seen filling the syringe (see 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 that is present on most commercially available catheters or deeper than 1 cm beyond the depth at which ascitic fluid was noticed in the lidocaine syringe.

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 image below).

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 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.

Advancing the catheter over the needle.

Advance catheter over the needle.

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

Attach the 60-mL syringe to the 3-way stopcock and aspirate to obtain ascitic fluid and distribute it to the specimen vials (see images and video below). Use the 3-way valve, as needed, to control fluid flow and prevent leakage when no syringe or tubing is attached.

Sample collection.

Sample collection. 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 images below).

Collecting tube. Vacuum bottle.

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, then reconnect and see if flow resumes. Rotating the catheter about the long axis can sometimes reinstitute flow in models with side ports.

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

Catheter removal.

The video below depicts ultrasound-assisted large-volume paracentesis.

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

PearlsDepending 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.[8] )

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 serum-ascitic albumin gradient [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-ga needle.

After proper antiseptic preparation and local anesthesia, a therapeutic tap can be performed with an intravenous 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 spontaneous bacterial peritonitis (SBP).[9, 10]

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 spontaneous bacterial peritonitis. [8]

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. [11]

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. [12]

ComplicationsComplications 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 viscous 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[13]

A prospective study of 171 patients undergoing paracentesis found that "major" complications occurred in 1.6% of procedures and included 5 episodes of bleeding and 3 infections, resulting in death in 2 cases. Major complications were associated with therapeutic but not diagnostic procedures and tended to be more prevalent in patients with low platelet counts (< 50 X 10(9)/L), patients who were Child-Pugh stage C, and patients with alcoholic cirrhosis.[6]

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, although no difference in survival has been noted relative to other plasma expanders.[14]

Periprocedural CareAnesthesiaLocal anesthesia is used. See Technique for details.

For more information, see Local Anesthetic Agents, Infiltrative Administration

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12. Kwok CS, Krupa L, Mahtani A, et al. Albumin Reduces Paracentesis-Induced Circulatory Dysfunction and Reduces Death and Renal Impairment among Patients with Cirrhosis and Infection: A Systematic Review and Meta-Analysis. Biomed Res Int. 2013;2013:295153. [Medline]. [Full Text].

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