Paracentesis and Diagnostic Peritoneal Lavage

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W10 Paracentesis and Diagnostic Peritoneal Lavage

Louis H. Alarcon

Paracentesis: Before Procedure

Anatomy

The site for paracentesis is in the abdomen, lateral to the rectus muscle in the lower quadrant midway between the umbilicus and the anterior superior iliac spine, avoiding prior surgical incisions. Ultrasound guidance is recommended to identify the site of largest volume of ascites and reduce the chance of injury to the intestines.

Procedure

• The patient should be supine. Bedside ultrasonography can be a valuable aid for localizing the largest collection of ascites and avoiding injury to the bowel and should be employed routinely. The patient should void or have a urinary bladder drainage tube inserted before the procedure. The area is cleansed, draped, and anesthetized.

• When a small volume of ascitic fluid is needed for diagnostic studies, an 18- or 20-gauge, 2- to 3-inch needle attached to a 20- to 50-mL syringe is inserted into the abdomen lateral to the rectus muscle in the lower quadrant, midway between the umbilicus and the anterior superior iliac spine, avoiding prior surgical incisions. The skin is retracted caudad while inserting the needle. When fluid is aspirated, the needle is stabilized and the fluid sample is obtained by syringe. After removal of the needle, the skin is released, causing the entrance and exit needle sites to form a “Z-track” that reduces the chance of ascitic fluid leakage.

• For large-volume paracentesis, a 14- to 16-gauge cannula-over-needle is employed. Once fluid is aspirated in the syringe, the needle is removed, leaving the plastic catheter in place, which is attached to plastic tubing and to a vacuum canister. Usually 4 to 6 L of ascites can be safely removed, although larger volumes have been removed.

• If it is necessary to place a catheter into the peritoneal cavity, a guidewire should be inserted into the peritoneal cavity through the needle; an 8.5F 40-cm polyurethane pigtail catheter should be guided into the peritoneal cavity over the wire and sutured in place.

• The aspirated fluid should be submitted for cell count, absolute polymorphonuclear neutrophil count, albumin, total protein concentration, Gram stain, and cultures. Optional studies, based on clinical suspicion, may include glucose concentration, amylase concentration, lactate dehydrogenase concentration, bilirubin concentration, and cytology.

After Procedure

Postprocedure Care

• The patient should be closely monitored for complications (see later), especially bleeding and peritonitis.

• If a pigtail catheter is left in place, it should be attached to a collection bag and monitored for bleeding or drainage of succus.

• Hypotension after paracentesis in cirrhotic patients can be associated with worsening of arteriolar vasodilation.¹ In the first few hours after large-volume paracentesis, there is a reduction in plasma levels of renin and aldosterone, an increase in atrial natriuretic peptide concentration, a reduction in cardiac filling pressures, and an increase in cardiac index.

• However, after 12 to 24 hours, these changes reverse, reflecting effective hypovolemia. Infusion of intravenous colloids, specifically albumin, has been shown to attenuate the hemodynamic consequences of paracentesis and the associated neurohumoral alterations.² However, no large randomized study has shown that routine expansion of plasma volume with a colloid solution confers a survival advantage.

• Infrequent:

• Bleeding:

• The incidence of significant hemorrhage from this procedure is about 1%, despite the fact that over 70% of patients have clotting parameter abnormalities.³ Therefore, it is usually unnecessary to normalize the prothrombin time before proceeding.⁴

• Serious complications such as bowel perforation are rare (0.1%)³:

• Peritonitis

• Bowel injury

• Injury to the bladder

• Injury to the epigastric vessels

Outcomes and Evidence

• Determining the etiology of ascites is based on the patient’s history, physical examination, liver function tests, ultrasonography, and ascitic fluid analysis. Abdominal paracentesis and ascitic fluid analysis should be an early step in the workup of patients with new-onset ascites. Paracentesis is also important to diagnose infection of ascitic fluid (i.e., peritonitis).

• Development of ascites is a common complication of cirrhosis, being more frequent than either encephalopathy and variceal hemorrhage in these patients. The median survival of cirrhotic patients with ascites is 2 years.⁵ Other causes of ascites besides cirrhosis include malignancy, heart failure, tuberculosis, renal failure, and pancreatic disease.

• The mainstays of treatment of ascites secondary to cirrhosis involve dietary sodium restriction (2 g/d) and oral diuretics (spironolactone and furosemide).

• The underlying etiology of liver disease should be corrected when possible, and ethanol consumption should be strongly discouraged. Abstinence from ethanol can normalize portal venous pressures in some patients with early ethanol-induced liver disease.⁶

• Patients with early cirrhosis and diuretic-responsive ascites should not be managed by serial paracentesis; rather, medical management should be employed. In the majority of patients, ascites can be controlled with medical management.

• In 5% to 10% of patients, ascites becomes resistant to medical treatment. The standard of care for management of refractory ascites is therapeutic paracentesis. This can be performed as often as every 2 weeks to control symptomatic ascites.

• Other options for managing refractory ascites include transjugular intrahepatic portosystemic shunt (TIPS) and liver transplantation. In a randomized trial of 60 patients comparing TIPS with repeated therapeutic paracentesis, the probability of survival without liver transplantation at 2 years was 58% in the TIPS patients as compared with 32% in the paracentesis patients.⁷ A smaller study of 25 patients randomized to TIPS or paracentesis showed the opposite: mortality was higher in the TIPS group.⁸

• Surgical portosystemic shunts and peritoneovenous shunts have fallen out of favor owing to high incidence of morbidity and mortality and to the development of hepatic encephalopathy.

• For patients with tense ascites, large-volume paracentesis rapidly relieves intraabdominal pressure. A single 4- to 6-L paracentesis can be performed safely and often does not require infusion of colloids.⁹ However, paracentesis does nothing to correct the etiology of the ascites, and ascites will recur if sodium restriction and diuretics are not instituted or fail. Referral for liver transplant evaluation should be considered in eligible patients with cirrhosis and refractory ascites.

• Infection of ascitic fluid often occurs in cirrhotic patients. When there is no surgically correctable etiology such as perforated viscus, the term spontaneous bacterial peritonitis is used. This diagnosis is made when there is a positive ascitic fluid culture or an ascitic fluid polymorphonuclear (PMN) cell count greater than 250 cells/mm³ in the correct clinical scenario without any evidence for an intraabdominal, surgically correctable etiology. The infection is usually monomicrobial. Polymicrobial infection suggests secondary peritonitis. Consideration of the diagnosis mandates paracentesis and evaluation of the ascitic fluid; a clinical diagnosis without paracentesis is inadequate.

Diagnostic Peritoneal Lavage: Before Procedure

Indications

• With the widespread use of focused abdominal sonography for trauma (FAST), the indications for diagnostic peritoneal lavage (DPL) are decreasing.

• Patients who have sustained blunt trauma and have no overt signs of acute abdominal injury or bleeding but require evaluation to rule out intraabdominal hemorrhage or hollow viscus injury

• Patients who are not candidates for computed tomography (CT) (e.g., owing to hemodynamic instability) or when FAST is unavailable or yields equivocal results

Contraindications

• The only absolute contraindication to performing a DPL is clinical condition of the patient mandating immediate laparotomy.

• Relative contraindications include previous abdominal surgery, cirrhosis, obesity, and coagulopathy.

• In patients with pelvic fractures or pregnancy, a supraumbilical incision should be performed.

Equipment

• Local anesthetic

• Chlorhexidine prep

• Sterile towels, gloves

• 10-mL syringe

• 8F to 9F 25-cm lavage catheter

• 2-0 polypropylene suture

Anatomy

DPL should be performed in the midline of the abdomen immediately below the umbilicus, or above the umbilicus in patients with pelvis fracture, suspected pelvic hematoma, or pregnancy. Prior surgical incisions should be avoided if possible.

Procedure

• The patient should be in the supine position. Gastric and bladder decompression tubes should be inserted to minimize the risk of injury to these organs. The periumbilical skin should be prepped and draped sterilely. Local anesthesia is injected into the site.

• DPL can be performed with an open, semi-open, or closed technique.

• The open technique employs a midline infraumbilical abdominal incision 2 to 5 cm in length; the incision should be supraumbilical if the patient has a pelvic fracture or is pregnant. A small incision is made in the midline abdominal fascia and peritoneum. An 8F to 9F 25-cm lavage catheter with side holes is inserted under direct visualization toward the pelvis.

• The closed method uses a Seldinger technique. A 16-gauge, 3-inch needle is inserted through a skin puncture and into the peritoneal cavity. A guidewire is passed through the needle into the peritoneal cavity. The lavage catheter is inserted over the wire.

• The semi-open technique involves incising the skin and fascia and then using a guidewire technique for inserting the catheter into the peritoneal cavity.

• Once the catheter is placed, aspiration should be attempted with a syringe.

• If 10 mL of blood is aspirated, the DPL is considered positive, and appropriate surgical intervention undertaken.

• Otherwise, 1 L of crystalloid solution is infused (10 mL/kg in pediatric patients) and then retrieved by gravity and sent to the laboratory for analysis.

• In general, the DPL is considered positive in blunt-trauma patients if:

• Red blood cell (RBC) count is greater than 100,000/mm³

• White blood cell (WBC) count is greater than 500/mm³

• Amylase concentration is greater than 100 IU/L

• Other positive findings include presence of bile or food particles or drainage of lavage fluid from the bladder drainage catheter, gastric tube, or thoracostomy tube.

• The sensitivity and specificity of the test are dependent on the threshold criteria for determining a positive test result.

• If the lavage is negative but there is a high index of suspicion for intraabdominal pathology, the DPL catheter can be left in place for repeat lavage to rule out delayed hemoperitoneum or intestinal perforation.

After Procedure

Complications

• Infrequent:

• Bowel or vascular injury occurs in less than 1%.¹

• Bladder injury

• Bleeding (cause for a false-positive DPL result)

• Wound infection

Outcomes and Evidence

• Evaluation of the abdomen is a critical component in the assessment of injured patients. Failure to identify intraabdominal injury results in preventable morbidity and mortality in trauma patients. The physical examination for abdominal injury is often hampered by alterations of the sensorium by substances such as ethanol and illicit drugs, injury to the central nervous system, or pain from other injuries. Also, a significant amount of blood can be present in the peritoneal cavity without obvious abdominal distention or peritoneal signs.

• DPL, CT, and ultrasonography have emerged as the main diagnostic modalities to evaluate trauma patients and currently have complementary roles. DPL was introduced by Root and colleagues in 1965 for evaluation of abdominal trauma.²

• In the era before CT and ultrasonography, DPL was the first well-established method to identify hemoperitoneum in trauma patients.

• DPL is primarily useful in diagnosing hemoperitoneum from blunt solid-organ injury, but it can also be helpful for the diagnosis of hollow viscus injury.

• For hemodynamically stable patients with an equivocal abdominal examination, associated neurologic injury, or painful injuries, abdominal CT is recommended as the diagnostic modality of choice and has all but eliminated the need for DPL in these patients.

• CT is also the preferred diagnostic method for determining whether nonoperative management of a solid-organ injury is appropriate.

• Furthermore, in stable patients with a positive DPL, follow-up abdominal CT should be considered. Thus, CT and DPL play complementary roles in evaluating stable patients after blunt abdominal trauma.

• For hemodynamically unstable patients, FAST and DPL are the preferred tests, with FAST rapidly gaining acceptance over DPL in many trauma centers as the preferred initial diagnostic modality.

• FAST and DPL are used to rule out hemoperitoneum as the cause of hemodynamic instability.

• In contrast to DPL, FAST can be used to identify pericardial tamponade.

• These tests can be performed expeditiously, and ongoing efforts at resuscitation and evaluation can occur simultaneously with the performance of the test.

• Because resuscitation is difficult during CT, CT is contraindicated when patients are hypotensive or hemodynamically unstable.

• DPL is also useful in certain clinical scenarios. Consider, for example, a head-injured patient needing an emergency craniotomy: DPL can be performed in the operating room at the same time as the craniotomy without interfering with the neurosurgical procedure.

• Controversy exists regarding the best way to manage blunt trauma patients with isolated evidence of free intraabdominal fluid by CT but without evidence of solid-organ injury.

• In a review of the literature, isolated free fluid was seen in 2.8% of over 16,000 blunt trauma patients studied with CT.³ Of these, only 27% underwent a therapeutic laparotomy, so some experts recommend serial abdominal examinations, whereas others recommend surgical exploration to rule out hollow viscus injury.

• DPL can be useful in the evaluation of patients with suspected perforated viscus. Very early after bowel perforation, the WBC count in the lavage fluid may be low; however, within a few hours after injury, the degree of inflammation is usually sufficient to increase the WBC count in lavage fluid to greater than 500 cells/mm³. The presence of bile, amylase, bacteria, or food particles in lavage fluid also confirms intestinal perforation.

• The use of DPL in the evaluation of hemodynamically stable patients with penetrating abdominal wounds remains controversial.

• A significant number of missed injuries remain undetected by this method. For example, Kelemen et al.⁴ reported a 21% false-negative rate for stable patients with abdominal gunshot wounds. Using a low RBC threshold (1000/mm³) has been described in an attempt to overcome this shortfall.⁵

• False-positive DPL leading to unnecessary laparotomy may occur in as many as 30% of cases.^1,⁶ This problem can be reduced by using CT as a complementary test in stable patients. The false-negative rate (i.e., failure to diagnose hemoperitoneum) is low. However, DPL is unable to detect retroperitoneal injuries (CT is the preferred test to detect retroperitoneal injuries for the stable patient) and is insensitive for detecting early hollow viscus and diaphragmatic injuries.

• One of the major problems with DPL is that the test is too sensitive. Only about 30 mL of blood in the peritoneal cavity is necessary to produce a positive DPL. In this era of selective management of solid-organ injuries, a significant number of nontherapeutic laparotomies would be performed on the basis of these DPL results unless diagnostic evaluation includes other modalities as well.

• Proponents of the open technique argue that it is safer, whereas proponents of the closed and semi-open methods argue that these approaches are more expeditious and can be safely performed by appropriately trained individuals.

• A large meta-analysis that aggregated results from 1126 patient trials showed that the incidence of major complications is not different for the different DPL techniques.⁷

• Failure to properly place the catheter and technical difficulties were more likely with the closed method, whereas procedure time was shorter with the open method (17.8 versus 26.8 minutes, respectively).

• Sensitivity, specificity, and accuracy were not different between the methods of catheter insertion.