Introduction: Ascites is defined as an abnormal accumulation of fluid in the abdominal cavity. Ascites is the most common complication of cirrhosis, with approximately 50% of patients with compensated cirrhosis developing ascites over the course of 10 years. After developing ascites that necessitates hospitalization, the risk of mortality increases to 15% at 1 year and nearly 50% at 5 years. Complications following the development of ascites include spontaneous bacterial peritonitis, dilutional hyponatremia, refractory ascites, and hepatorenal syndrome. Development of these complications markedly impacts the likelihood of survival (Figure 1). Once ascites develops, patients should be referred for consideration of liver transplantation.
History and Physical Examination: In the United States, in approximately 85% of patients with ascites, cirrhosis is the cause, but 15% have a non-hepatic cause of fluid accumulation (Figure 2). Approximately 5% of patients have “mixed” ascites or have two or more causes for the ascites, typically cirrhosis plus another reason. In addition to assessing for risk factors for liver disease, history or risk factors for malignancy, heart failure, nephrotic syndrome, thyroid myxedema, recent abdominal surgery, and tuberculosis should be elicited. The presence of bulging flanks (Figure 3) suggests the presence of ascites. In order for the flank dullness to be appreciated on physical exam, at least 1500 mL of ascites needs to be present. The shifting dullness test (Figure 4) improves the diagnostic sensitivity of physical examination for detecting the presence of ascites; this test has 83% sensitivity and 56% specificity in detecting ascites. An abdominal ultrasound can be done to confirm the presence of ascites when suspected on history and physical examination.
Diagnostic and Therapeutic Paracentesis: The evaluation for the etiology of clinically apparent ascites should begin with an abdominal paracentesis with appropriate ascitic fluid analysis. In addition, at time of any hospital admission, a diagnostic paracentesis should be done to assess for infection. Patients do not need to be fasting for this procedure. Prophylactic blood products, including fresh frozen plasma and platelets, do not routinely need to be given prior to a paracentesis in patients with cirrhosis with associated thrombocytopenia and coagulopathy. The tests for coagulation do not reflect the true bleeding risk in these patients, as there is diminished production of both procoagulants and anticoagulants. There are no threshold criteria for coagulation parameters or platelet count for a paracentesis. This procedure, however, should be avoided in the setting of clinically evident hyperfibrinolysis or disseminated intravascular coagulation. Epsilon aminocaproic acid (Amicar) can be given to treat hyperfibrinolysis. Desmopressin (DDAVP) may be used in patients with renal failure.
- Patient Position and Site for Paracentesis: The procedure is usually performed with the patient lying supine. As described in the most recent practice guidelines from the American Association for the Study of Liver Diseases, the left lower quadrant of the abdomen is the preferred site for the paracentesis and the exact insertion site should be located 2 fingerbreadths (3 cm) cephalad and 2 fingerbreadths (3 cm) medial to the anterior superior iliac spine (Figure 5). Some experts choose the midline of the abdomen midway between the pubis and umbilicus, but this site is considered less preferable in obese patients (due to the increase in midline wall thickness) and in patients with lower volume-ascites (a smaller pool of fluid in the midline than in the lateral quadrant). The right lower quadrant may be complicated by a dilated cecum or appendectomy scar. Extreme care should be taken to avoid the inferior epigastric arteries (Figure 6), which are located halfway between the pubis and anterior superior iliac spines and run cephalad in the rectus sheath, as well as visible collaterals in the abdominal wall. In addition, caution is needed in patients who have a palpable spleen, as it could be ruptured with the left lower quadrant approach. If the ascitic fluid is difficult to find on physical examination or if there is significant bowel dilatation, ultrasonography can be used to help locate the fluid pocket and visualize the spleen and other structures to guide this procedure. Paracentesis sites should be chosen distant from abdominal surgical scars or under image guidance.
- Choosing Needle for Insertion: A 1.0 or 1.5 inch 21 or 22 gauge single hole needle (or 3.5 inch 22 gauge needle for obese patients) can be used for a diagnostic paracentesis, whereas a 15 or 16 gauge multi-hole two piece needle set can be used for therapeutic paracentesis, involving the removal of more than 5 L of ascites for symptomatic relief from abdominal pain, early satiety, and/or dyspnea.
- Preparation and Insertion Technique: The site should be cleansed with iodine or chlorhexidine solution and the skin should be anesthetized using 1% lidocaine solution via a 25 or 27 gauge needle. Sterile gloves should be worn to avoid contamination of samples. After raising a wheal in the superficial skin, 3 to 5 mL of lidocaine is used to anesthetize the soft tissue tract using the Z-track technique (the skin is pulled downward with the non-dominant hand, while inserting the needle with the other hand (Figure 7), to decrease the risk of ascitic fluid leak. The skin is not released until the needle enters the peritoneal cavity, indicated by the aspiration of ascitic fluid. The paracentesis needle is inserted along the same line using the Z-track technique. A scalpel can be used to create a skin nick to facilitate the entry of the larger gauge needle if therapeutic paracentesis is needed. After entry into the peritoneum, the angle and depth of the paracentesis needle should be stabilized. The suction applied should be intermittent rather than continuous to avoid pulling in omentum or bowel into the needle tip and obstructing flow. If the flow of liquid stops, the patient can be slowly repositioned in effort to pool more fluid near the needle tip.
- Fluid Collection and Samples: For a diagnostic tap, a minimum of 25 mL of fluid should be collected. One to two mL of ascitic fluid should be injected into a purple-top (EDTA) tube for the cell count and differential tests. Three to four mL of fluid should be directed into a red top tube for chemical analyses. Fluid should be directly inoculated into blood culture bottles at the bedside, typically 10 mL into each bottle. If needed, an additional 50 mL of fluid can be sent in a sterile syringe or cup for cytology or other tests. Vacuum bottles are used to assist the speed of fluid removal in a therapeutic paracentesis.
- Paracentesis Complications: The paracentesis procedure is generally very safe, with only a 1% risk of abdominal wall hematoma and a less than 0.5% risk of mortality, even in patients with coagulopathy related to liver disease. Post-paracentesis ascitic fluid leak can occur in 5% of patients, especially when larger needles are used. More serious complications such as hemoperitoneum and bowel perforation are extremely rare, reported in less than 1 in 1000 cases. Infections due this procedure are very rare, mostly in cases of bowel injury, and are typically well tolerated.