Chapter 65. Paracentesis

The word ascites is derived from the Greek askos meaning “bag” or “sac.” Ascites, an abnormal accumulation of fluid in the abdominal cavity, has important implications diagnostically, therapeutically, and prognostically. Cirrhosis of the liver, which is usually related to alcoholism, accounts for 75% of cases of ascites; malignancy accounts for an additional 10% to 12%, and cardiac failure for another 5%. The remaining cases have a variety of etiologies.1 Unfortunately, the physical examination is not very reliable when it comes to detecting ascites, making paracentesis and ultrasound (US) important clinical tools.2 US-guided paracentesis has two key benefits. It not only facilitates performance of the procedure, but it also identifies patients in whom the procedure is not warranted or could potentially be harmful.3

Peritoneal aspiration of ascitic fluid or paracentesis was first described by Saloman in the early twentieth century.4 With the introduction of diuretics as well as a fear of procedure-related complications, paracentesis fell out of favor in the 1950s, being replaced by medical management. At that time, large-bore needles were being used and complication rates were significant. Clinical studies published in the late 1980s demonstrated that performing a paracentesis was, in fact, a safe procedure.5,6 Nowadays, the procedure is commonplace in Emergency Departments.

Paracentesis is an important diagnostic tool for patients with new-onset ascites to determine its etiology and in those patients with long-standing ascites to detect the presence of infection. Spontaneous bacterial peritonitis can be a very subtle disease. Infection occurs in as many as 27% of cirrhosis patients admitted for evaluation of symptoms associated with their ascites.7 It is well known that some patients with spontaneous bacterial peritonitis are asymptomatic, making peritoneal fluid aspiration, analysis, and cultures imperative.8 In addition to the diagnostic usefulness of paracentesis, large volumes of ascitic fluid can be removed therapeutically by this procedure in order to improve a patient's respiratory status and comfort level from the pressure of tense ascites. This often occurs in patients with end-stage liver disease as well as in some cases of malignancy. Malignant ascites may occur with carcinoma of the ovary, pancreas, stomach, colon, breast, testes, and a variety of sarcomas and lymphomas.

The gross anatomy of the abdomen is well known to the Emergency Physician and is important to review in preparing for a paracentesis. The abdominal cavity is lined by the peritoneum and is protected from the environment by the abdominal wall musculature, fat, and skin. The right and left rectus muscles, which are nourished by the epigastric vessels, meet in the midline at the avascular linea alba. The umbilicus is located along the lower portion of the linea alba. The layers of the anterior abdominal wall structures vary above and below the level of the anterior superior iliac spine (Figure 65-1).

The liver sits in the upper right quadrant; when enlarged, it can be palpated in the lower right quadrant. The spleen is normally contained in the upper left quadrant, but when it is enlarged, it can extend into the left lower quadrant (LLQ) of the abdomen. The intestines occupy most of the abdominal cavity and are not rigidly adherent, allowing them to move about in the abdominal cavity. The bladder sits in the pelvis but can enter the abdominal cavity when it is distended with urine.

The abdominal cavity is divided into compartments according to mesenteric attachments. Ascitic fluid can be found anywhere in the peritoneal cavity. The location of the ascitic fluid depends primarily upon the amount of fluid present and the patient's position. Fluid follows the law of gravity. Small amounts of fluid generally accumulate in the cul-de-sac and pericolic gutters. Large amounts of fluid can be found bathing the intestines (Figure 65-2). There can also be distinct pockets of fluid in areas of bowel adhesions or scarring. These localized areas of fluid are typically found in those patients who have had previous surgery, trauma, or infection.

Although paracentesis is easily performed blindly, US can provide several benefits. US is diagnostically useful to ensure there is enough fluid to perform a paracentesis. It will identify and help avoid solid organs, masses, and vascular structures. If there are bowel adhesions, US will also identify areas where the bowel is adherent and puncture should not occur. In obese patients, US can measure the soft tissue thickness to the peritoneum, locate the thinnest entry point, and determine the needle length required. US can be used to position the patient so that the maximum amount of fluid collects at the sampling site.

A paracentesis can be performed for diagnostic or therapeutic purposes. A paracentesis or “abdominal tap” is warranted in a patient with new-onset ascites to establish the etiology of the fluid. A patient with a history of ascites may need the procedure if they have associated signs and symptoms suggestive of infection such as fever, dyspnea, abdominal pain, encephalopathy, renal impairment, or peripheral leukocytosis.9 A paracentesis can be performed therapeutically for patients in whom medical management with diuretics has not been successful. It is most commonly performed when an intraperitoneal infection is suspected. Clinical guidelines recommend that patients with ascites admitted to the hospital whether or not they have symptoms of spontaneous bacterial peritonitis should undergo a paracentesis.9,10 Paracentesis has been used to aid in the diagnosis of ruptured ectopic pregnancy, bowel perforation, and hemoperitoneum due to trauma. More accurate diagnostic procedures should be used rather than a paracentesis for these conditions if they are available.

There are no absolute contraindications to performing a paracentesis. The relative contraindications include pregnant patients or patients who have a history of abdominal surgery, a current bowel obstruction, a coagulopathy, or thrombocytopenia. Pregnancy is listed because the gravid uterus may fill the space where the procedure is normally performed. If a paracentesis is indicated, it should be performed superior to the uterine fundus. It is important to avoid sites of previous surgical incisions, because adhesions may fix the bowel wall to the abdominal wall, thus increasing the possibility of perforation. Many patients who are subjected to a paracentesis have underlying liver disease and resultant coagulopathies. Some advocate that patients with thrombocytopenia or an abnormal international normalized ratio (INR) should have platelet transfusions or factor replacement prior to performing a paracentesis. This practice is controversial and there are no controlled data to support these contentions.11 Many, however, would suggest using an infraumbilical midline, also known as a linea alba, approach in coagulopathic patients. This area is free of any vasculature, thus reducing the possibility of bleeding complications. A recent study in which the majority of ascites patients had a paracentesis performed in the LLQ did not demonstrate any bleeding complications.12 With this in mind, and given that the abdominal wall is thinner and ascitic fluid pools more in the LLQ, this location may be chosen over the infraumbilical approach when US is not being used to guide the procedure.13

• Protective eyewear
• Sterile gloves and gown
• Cap and mask
• Povidone iodine or chlorhexidine solution
• Sterile 4 × 4 gauze
• Sterile drape
• Local anesthetic solution with epinephrine
• 25 or 27 gauge needle to anesthetize the skin
• 10 mL syringe for anesthetic
• Choice of needle options: 18 to 22 gauge needle, 3½ in. needle or spinal needle
• Seldinger-type guidewire kit
• Catheter-through-the-needle
• Catheter-over-the-needle—consider Caldwell needle
• Large syringe(s) for fluid collection (20 to 60 mL)
• Intravenous tubing or blood collection tubing if vacuum bottles are being used
• Collection bottles (vacuum) or collection bag
• Adhesive dressing
• Three-way stopcock
• Blood collection tubes for white blood cell (WBC) count, electrolytes, albumin, pH, etc.
• Blood culture bottles (aerobic and anaerobic)
• Sterile specimen container for cytology (optional)
• US machine and probe
• Sterile US gel
• Sterile US probe cover

Commercially available paracentesis kits are available. These contain all the required equipment except the collection bottles. They include the sterile drapes and local anesthetic solution. These are convenient and relatively inexpensive.

A general-purpose curvilinear or phased-array US probe provides the best combination of penetration and field of view into the abdomen. A linear probe can be used for thin, small adults, and children.

Explain the procedure, its risks, and its benefits to the patient and/or their representative. Obtain an informed consent for the procedure. The patient's bladder should be empty. Use an US machine to check for a full bladder or place a Foley catheter to decompress the bladder if the patient is unable to urinate voluntarily. Placement of a nasogastric tube is recommended, although not routine. It prevents an iatrogenic perforation if the stomach is dilated or if a concomitant bowel obstruction is present.

There are two recommended areas of entry for the paracentesis needle (Figure 65-3). The first site is in the midline and 2 cm below the umbilicus. Alternatively, the region 4 to 5 cm superior and just medial to the anterior superior iliac spine in one of the lower quadrants may be used. Some physicians choose the right lower quadrant to avoid the sigmoid colon and spleen. Others choose the LLQ to avoid the cecum and liver. Remember to exercise caution in the region of a scar, prominent veins, caput medusa, or over an area of inflamed or infected skin to minimize complications. US-assisted paracentesis is recommended if an US machine is readily available. Not only can US assist in identifying the ideal fluid pocket but also hopefully avoid a “dry tap”.3

Place the patient sitting upright for a midline or linea alba approach, lying in the right lateral decubitus position for a right lower quadrant approach, or lying in the left lateral decubitus position for a LLQ approach. Another position one might consider is having the patient assume a hand-knee or “crawling” position. This position, however, is awkward for the Emergency Physician performing the procedure. Remember that the fluid will pool in dependent areas and the bowel will float on top of it—barring any adhesions or masses.

Prepare the patient. Clean the skin around the chosen puncture site of any dirt and debris. Apply povidone iodine or chlorhexidine solution and allow it to dry. Apply sterile drapes to delineate a sterile field. Inject 2 to 5 mL of local anesthetic solution subcutaneously and along the needle insertion tract. Allow 3 to 5 minutes for the local anesthetic to take effect.

Z-Tract Technique

A “Z-tract” is used to decrease the possibility of an ascitic fluid leak, especially in patients with tense ascites (Figure 65-4). This is the preferred method for inserting the needle. This technique should also be followed when using the other techniques described below. Apply traction on the skin cephalad or caudad to the needle insertion site so that the skin is pulled taut when the needle enters the peritoneum (Figures 65-4A & B). The idea is that when the skin tension is released, the skin returns to its normal position and seals off the pathway of the paracentesis needle.

Apply an 18 to 22 gauge, 3½-in needle or spinal needle to a 60 mL syringe. Slowly insert and advance the needle perpendicular to the skin (Figure 65-4A) or at 45° to the skin and aimed caudally (Figure 65-4B). Apply negative pressure to the syringe as it is being advanced. A loss of resistance should be felt as the needle enters the peritoneal cavity. Stop advancing the needle when ascitic fluid enters the syringe. Continue to aspirate until the syringe is one-half to three-fourths filled with fluid. Depending on the size of syringe consider using a three-way stop cock so syringes can be removed as they are filled.

The omentum, a loop of bowel, peritoneal fat, or other tissue may be occluding the needle tip if ascitic fluid suddenly stops flowing into the syringe. Release the plunger of the syringe. Reattempt to aspirate. If fluid still will not flow, inject 1 to 2 mL of ascitic fluid back into the peritoneal cavity and then reattempt to aspirate. Reposition the needle if ascitic fluid still does not flow into the syringe. Never reposition the needle while the sharp tip is within the peritoneal cavity. The needle can lacerate the bowel, the omentum, or a blood vessel. Withdraw the needle to the dermis, reposition it, and then readvance it into the peritoneal cavity. The Caldwell needle appears to be superior to a conventional angiocatheter needle when it comes to problems with fluid return. The Caldwell needle's unique design with fenestrations on the side is believed to allow for continued flow despite occlusion of the needle tip.14,23

Note the color and clarity of the ascitic fluid. Aspirate 30 to 50 mL if the procedure is being performed for diagnostic purposes. Withdraw the needle after obtaining the fluid. Immediately place the fluid into the appropriate collection tubes and culture bottles.15 If the reason for the paracentesis is therapeutic and there is a large collection of fluid that must be drained, hold the needle or catheter securely and remove the syringe. An assistant can place the sample into laboratory containers. Connect the needle or catheter to intravenous tubing. Connect the other end of the intravenous tubing to a suction bottle or bag in order to drain off the desired amount of ascitic fluid. Remove the needle or catheter once the procedure has been completed. Removal results in the formation of the Z-tract, so that ascitic fluid will not leak from the skin (Figure 65-4C). Apply a bandage to the skin puncture site. Consider a compression dressing with an occlusive bandage if fluid is oozing from the puncture site.

Seldinger Technique

First described by Seldinger in 1953, this technique allows for the placement of a catheter over a wire (Figure 65-5). The wire used must be longer than the catheter. The needle used to insert the wire can be short and of a smaller gauge than the catheter. Materials needed for catheter insertion are commercially available in a prefabricated kit. The Seldinger technique is most commonly used for central venous catheter insertion.

Choose the puncture site and prepare the patient for the procedure. Insert the thin-walled introducer needle in a Z-tract manner while applying negative pressure to the syringe (Figure 65-5A). The introducer needle has a tapered hub on the proximal end to guide the wire into the needle lumen. Avoid using a standard hypodermic needle, as it will not allow for the passage of the guidewire. A flash of fluid in the needle hub signifies that the tip of the needle is within the peritoneal cavity (Figure 65-5A). Advance the needle an additional 2 to 3 mm. Hold the needle in place securely and remove the syringe.

Occlude the needle hub with a sterile gloved finger. This will prevent air from entering and ascitic fluid from exiting. Insert the guidewire through the hub of the needle (Figure 65-5B). Advance the guidewire to the desired depth, ensuring that it is at least several centimeters beyond the beveled end of the needle. Always have at least one hand holding the guidewire at all times to prevent it from slipping completely into the peritoneal cavity. Hold the guidewire securely in place. Remove the needle over the guidewire (Figure 65-5C). Make a small nick in the skin adjacent to the guidewire with the #11 scalpel blade included in the kit (Figure 65-5D). Direct the sharp edge of the scalpel blade away from the guidewire to avoid nicking the guidewire.

Place the dilator through the sheath (or catheter) to form a unit. Advance the dilator and sheath unit over the guidewire (Figure 65-5E). Continue to advance the dilator and sheath unit over the guidewire and into the peritoneal cavity (Figure 65-5F). A twisting motion may aid in its advancement through the skin and into the peritoneal cavity (Figure 65-5F). Advance the unit until the hub of the sheath is against the skin. Hold the hub of the sheath securely. Remove the guidewire and dilator as a unit (Figure 65-5G). Attach a syringe to the hub of the sheath (Figure 65-5H).

Aspirate fluid from the sheath to confirm intraperitoneal placement. Hold the hub of the sheath securely and remove the syringe. Pass the syringe to an assistant to place the sample into laboratory containers. Connect the hub of the sheath to intravenous tubing. Connect the other end of the intravenous tubing to a suction bottle or bag in order to drain off the desired amount of fluid. An alternative is to attach a three-way stopcock to the distal end of the intravenous tubing. A syringe may then be attached to the stopcock to withdraw laboratory samples or “pump out” the ascitic fluid into a nonsterile container. Remove the sheath once the procedure is completed. Apply a bandage to the skin puncture site. While this technique seems complicated at first glance, it is easy to learn and can be performed in a few minutes by an experienced Emergency Physician.

Catheter‐Through‐the-Needle Technique

This system is used most commonly for central venous access. Select a catheter size that is appropriate for the patient and the site of entry. Packaged with each catheter are a needle and a needle guard. The needle will have an inner diameter that is slightly larger than the outer diameter of the catheter. The needle guard has a beveled channel in which the needle can reside. The needle guard hinges closed over the needle to hold it securely and prevent the needle from shearing the catheter.

Choose the puncture site and prepare the patient for the procedure. Place the needle on a tuberculin syringe. Insert the needle through the skin in a Z-tract manner and into the peritoneal cavity while applying negative pressure to the syringe (Figure 65-6A). A flash of fluid in the syringe confirms that the tip of the needle is within the peritoneal cavity. Advance the needle an additional 2 to 3 mm to ensure that the tip of the needle is completely within the peritoneal cavity. Securely grasp and hold the needle with the nondominant hand. Remove the syringe with the dominant hand. Immediately place the nondominant thumb over the needle hub to prevent air from entering and fluid from exiting.

Insert the catheter through the hub of the needle (Figure 65-6B). Advance the catheter through the needle until the desired length of catheter is within the peritoneal cavity. If the catheter will not advance, remove the catheter and needle as a unit. Never withdraw the catheter through the needle. The sharp bevel of the needle may cut the catheter as it is being withdrawn and result in a catheter embolism in the peritoneal cavity.

Withdraw the needle over the catheter (Figure 65-6C). Do not allow the catheter to be withdrawn through the needle. Continue to withdraw the needle until the tip is completely outside the skin. Apply the needle guard over the needle (Figure 65-6D). Attach a syringe onto the hub of the catheter. Aspirate fluid from the catheter to confirm intraperitoneal placement. Hold the hub of the catheter securely and remove the syringe. Pass the syringe to an assistant to place the sample into laboratory containers. Connect the catheter to intravenous tubing. Connect the other end of the tubing to a suction bottle or bag in order to drain off the desired amount of fluid. An alternative is to attach a three-way stopcock to the distal end of the tubing. A syringe may then be attached to the stopcock to withdraw laboratory samples or “pump out” the ascitic fluid into a nonsterile container. Remove the catheter once the procedure is completed. Apply a bandage to the skin puncture site.

The main disadvantage of this technique is the possibility of the needle tip shearing off the catheter and resulting in a catheter embolism. This can be prevented by not withdrawing the catheter through the needle and applying the needle guard immediately after the needle is withdrawn from the skin. Another disadvantage is that the contaminated needle must be handled to some extent, creating a potential risk for needle-stick injuries.

Catheter‐over‐the-Needle Technique

The catheter-over-the-needle systems are most commonly used for peripheral venous access. The infusion catheter fits closely over a hypodermic needle. The needle and the catheter are advanced as a unit into the peritoneal cavity. They are inexpensive, come in a variety of diameters and lengths, and are widely available. Versions designed to minimize accidental needle-stick injuries are available, and their use is encouraged (Figure 47-7B). Placement of these catheters is usually quick and simple. Consider using a Caldwell needle with fenestrations on the side to help minimize problems with the flow of fluid.

Choose the puncture site and prepare the patient for the procedure. Insert the catheter-over-the-needle through the skin in a Z-tract manner and into the peritoneal cavity (Figure 65-7A). A flash of fluid in the hub of the needle confirms that the tip of the needle is within the peritoneal cavity. Advance the catheter-over-the-needle an additional few millimeters to ensure that the catheter is within the peritoneal cavity. Hold the hub of the needle securely. Advance the catheter over the needle until its hub is against the skin (Figure 65-7B). Withdraw the needle and syringe as a unit. Attach a syringe onto the hub of the catheter (Figure 65-7C). Aspirate fluid from the catheter to confirm intraperitoneal placement. Hold the hub of the catheter securely and remove the syringe. Pass the syringe to an assistant to place the sample into laboratory containers. Connect the catheter to intravenous tubing. Connect the other end of the tubing to a suction bottle or bag in order to drain off the desired amount of fluid. An alternative is to attach a three-way stopcock to the distal end of the tubing. A syringe may then be attached to the stopcock to withdraw laboratory samples or “pump out” the ascitic fluid into a nonsterile container. Remove the catheter once the procedure is completed. Apply a bandage to the skin puncture site.

The use of US increases the success rates for performing a paracentesis and decreases complications.22 US may be used to assist or guide the paracentesis. A static technique is used to identify the skin puncture site and ascitic fluid location. The remainder of the procedure is “blind” using one of the above-described techniques. If ascites is not aspirated, the US probe can be placed back on the abdomen to locate the needle and determine if it is off target or not long enough to reach the peritoneal cavity. Occasionally, a dynamic technique is used and the needle inserted using real-time US.

Position the patient. Clean and prep the skin. Scan longitudinally and transversely with the US probe to survey each potential needle entry site (Figure 65-8). Ascites appears anechoic (black) and outlines the loops of bowel (Figure 65-9). The bowel may be seen undulating in the ascites as a result of peristalsis. Without ascites, individual loops of bowel cannot be visualized.

Note the amount of fluid and the presence of any structure that might make a particular site undesirable. If no site seems suitable, try repositioning the patient. Note the depth from the skin surface to the fluid. Choose a site with the most fluid at the least depth. Position the US probe so that the target is in the middle of the US view screen. The entry site will now be under the center of the probe. Mark the skin, wipe off the US gel, re-prep the area, and proceed with the procedure. If difficulties are encountered, use the probe to determine the needle's location (Figure 65-10).

Do not mistake a cystic fluid collection or the bladder for ascites. Ascites will outline individual bowel loops and appears in many places around the abdomen. Fluid in a cyst or the bladder has rounded borders and is localized. Loculated ascites will occasionally mimic a cyst but will still outline the bowel.

Once the procedure is completed, the puncture site should be bandaged. The site will occasionally ooze fluid in patients with tense ascites. These patients should be directed to change their dressings regularly. Occlusive tape can be helpful in preventing the fluid from leaking onto the patient's clothing and bedding. At times, a simple mattress or figure-of-eight suture is necessary to control the drainage. More recently, Emergency Physicians have used a tissue adhesive such as Dermabond, Indermil, or Histoacryl to help control a fluid leak. The patient may be discharged home if the purpose of the paracentesis was to relieve tense ascites and no signs or symptoms of spontaneous bacterial peritonitis exist and the fluid analysis is unremarkable. The patient should immediately return to the Emergency Department if they develop abdominal pain, nausea, vomiting, abdominal distention, or a fever.

The patient will require hospitalization and intravenous antibiotics if spontaneous bacterial peritonitis is suspected or diagnosed. Empiric antibiotics that cover gram-negative enterics (of which Escherichia coli is the most likely) and streptococcal species (including Enterococcus) should be administered in the Emergency Department. A third-generation cephalosporin, such as cefotaxime, covers the most common causative agents in this disorder and should be administered.9 Ampicillin may be added if Enterococcus is suspected. Check previous culture results for antibiotic sensitivities if the patient has a history of spontaneous bacterial peritonitis.

Complications from abdominal paracentesis are infrequent and rarely serious. However, known complications include shearing of the peritoneal catheter, abdominal wall hematoma, hemoperitoneum, bowel perforation, infection, persistent ascitic fluid leak, and systemic hemodynamic compromise.

Although bleeding is a potential complication of paracentesis, administration of prophylactic blood products such as fresh frozen plasma does not appear to be warranted.16 Spontaneous hemoperitoneum secondary to mesenteric variceal bleeding has been reported to occur in patients receiving large-volume (i.e., >4000 mL) paracentesis.17 Patients who developed this complication have had advanced cirrhosis with refractory ascites, previous large-volume paracentesis, and hemorrhagic shock without evidence of gastrointestinal bleeding. Mortality for this complication is exceedingly high. An additional vascular complication, an inferior epigastric artery pseudoaneurysm, has been described as a result of a therapeutic paracentesis.18

Perforation of the bowel during paracentesis is rare. Additionally, most of these injuries are self-sealing and develop no further problems. Generalized peritonitis and abdominal wall abscesses have also been reported and are exceedingly rare. Do not move the needle when it is within the peritoneal cavity in order to avoid lacerating the bowel wall.

Ascitic fluid may continue to leak from the site of paracentesis. A simple suture at the site may correct the problem. Patients with persistent leaks should also be evaluated for peritonitis.

Rapid removal of significant amounts of ascitic fluid has been found to cause hemodynamic compromise. Initially, removal of large amounts of ascites causes improvement in circulatory function, likely related to both mechanical (i.e., improved cardiac venous return) and neurohumoral factors. However, total paracentesis in cirrhotic patients may cause delayed (i.e., >12 to 24 hours postprocedure) effective hypovolemia by accentuation of baseline arteriolar vasodilation through neurohumoral mechanisms.19 The literature suggests that some of the postparacentesis circulatory dysfunction may be avoided by pretreating patients with an intravenous colloid such as albumin.20 This is not a universally accepted practice.

Normal ascitic fluid should appear clear with a yellow color. Increased turbidity may suggest infection, elevated triglyceride levels, or other particulate matter. Sanguinous fluid is present in patients with malignancy, intraperitoneal bleeding from the intraabdominal organs (spontaneous or iatrogenically introduced), or tuberculous peritonitis.

The specific analytical tests ordered on ascitic fluid should reflect the Emergency Physician's clinical suspicion (Table 65-1). Simple analysis of fluid with a cell count and differential, routine cultures, and albumin concentration are all that is necessary in patients with uncomplicated cirrhosis. These initial tests can be supplemented depending upon clinical suspicion. An ascitic fluid pH <7.35 and a blood–ascitic fluid pH gradient ≥0.10 can aid in the diagnosis of spontaneous bacterial peritonitis.7 Total protein, glucose, LDH, amylase, triglyceride, and bilirubin levels are not helpful except in select circumstances and are not warranted on a routine basis. The serum-ascites albumin gradient is approximately 97% accurate in indicating portal hypertension.5,21 The gradient is calculated by subtracting the ascitic fluid albumin concentration from the simultaneously measured serum albumin concentration. A gradient of ≥1.1 g/dL suggests portal hypertension as the etiology of the ascites (Table 65-2). A gradient of <1.1 g/dL suggests that the patient does not have portal hypertension and that the ascites has some other etiology (Table 65-2).

Peritoneal carcinomatosis should be suspected and cytology ordered in those patients with a history of breast cancer, colon cancer, gastric cancer, pancreatic cancer, or the suspicion of undiagnosed malignancy and ascites. Cultures for mycobacteria are approximately 50% sensitive. They should be ordered when the suspicion for tuberculous peritonitis is high, as in patients who have immigrated from endemic areas or have an immunocompromised status.

Patients with uncomplicated ascites secondary to cirrhosis should have an ascitic fluid WBC count < 500 cells/mm3. The cells should be predominantly lymphocytes and there should be no clinical evidence of peritonitis. If an infection is suspected, a WBC count of >250 cells/mm3 with greater than 50% polymorphonuclear leukocytes confirms spontaneous bacterial peritonitis. In order to adjust for significant blood in a specimen (RBC > 10,000 cells/mm3), subtract one neutrophil per 250 RBC.9 A Gram's stain is usually not helpful other than in the case of spontaneous bowel rupture. Otherwise, the concentration of bacteria is too low to justify utilization of a Gram's stain. All potentially infected ascitic fluid should be cultured by directly inoculating blood culture bottles at the bedside.15,23

Paracentesis is a safe procedure that is common in the practice of Emergency Medicine. There are few relative contraindications to its performance. It is most commonly performed diagnostically to detect spontaneous bacterial peritonitis. It can also be performed therapeutically for symptomatic relief in patients with tense ascites. Complications, although they do occur, are rare.