Overview
Definition:
Paracentesis is a minimally invasive procedure involving the withdrawal of fluid from the peritoneal cavity
It can be performed for diagnostic purposes (e.g., to analyze ascites fluid) or for therapeutic relief of symptoms caused by large-volume ascites.
Epidemiology:
Ascites, the primary indication for paracentesis, is most commonly associated with cirrhosis (over 80% of cases), but also occurs in heart failure, malignancy, nephrotic syndrome, and infections like tuberculosis
The prevalence of ascites is directly linked to the underlying etiology.
Clinical Significance:
Paracentesis is crucial for diagnosing the cause of ascites, guiding management of liver disease, and alleviating symptomatic discomfort, including abdominal distension, early satiety, and dyspnea
Proper perioperative support is vital to minimize complications and ensure patient safety.
Indications
Diagnostic Indications:
Suspicion of spontaneous bacterial peritonitis (SBP)
Assessment of malignant ascites
Evaluation of new-onset ascites of unknown etiology
Investigation of chylous or bloody ascites.
Therapeutic Indications:
Symptomatic relief of large-volume ascites causing significant abdominal distension, dyspnea, early satiety, or pain
Management of tense ascites that fails to respond to diuretic therapy.
Contraindications:
Absolute: Uncorrected coagulopathy (INR > 2.5 or platelet count < 50,000/µL), severe thrombocytopenia, abdominal wall cellulitis at the insertion site
Relative: Significant abdominal distension with ileus, extensive intra-abdominal adhesions, pregnancy, morbid obesity, uncooperative patient.
Preoperative Preparation
Patient Assessment:
Thorough history and physical examination focusing on ascites severity, symptoms, and underlying etiology
Assess for signs of hepatic encephalopathy, variceal bleeding, and infection.
Laboratory Investigations:
Complete blood count (CBC) with differential and platelet count
Coagulation profile (PT/INR, aPTT)
Serum electrolytes, BUN, creatinine
Liver function tests (ALT, AST, bilirubin, albumin, total protein)
Serum-ascite albumin gradient (SAAG) calculation.
Imaging:
Abdominal ultrasound is often used to confirm the presence of ascites, guide needle insertion site, and assess for loculations or masses
CT scan may be useful in cases of suspected malignancy or complex ascites.
Medication Review:
Review and adjust diuretic therapy
Administer prophylactic antibiotics if SBP is suspected or in patients with high risk for SBP (e.g., low SAAG, history of SBP)
Ensure adequate hydration and correct electrolyte imbalances.
Informed Consent:
Detailed explanation of the procedure, its risks (bleeding, infection, bowel perforation, fluid leak, electrolyte disturbances), benefits, and alternatives
Obtain written informed consent.
Procedure Steps
Patient Positioning:
Patient is typically positioned supine or in a semi-recumbent position (30-45 degrees) to allow fluid to accumulate in the lower quadrants
A slight left lateral decubitus position may be used for flank fluid collection.
Site Selection:
Choose an area with maximal fluid accumulation, typically in the left or right lower quadrant, avoiding surgical scars, masses, or superficial blood vessels
The mid-inguinal point or the line midway between the umbilicus and the anterior superior iliac spine is commonly used.
Aseptic Technique:
Perform sterile preparation of the skin and sterile draping of the operative field
Local anesthesia (e.g., lidocaine 1-2%) is infiltrated into the skin, subcutaneous tissue, and peritoneum.
Needle Insertion:
A 20-22 gauge needle or a blunt-tipped cannula (e.g., Venous Access Catheter) is inserted perpendicular to the skin
For diagnostic paracentesis, collect 30-100 mL of fluid in sterile tubes (serology, microbiology, cytology)
For therapeutic paracentesis, a larger bore catheter or a drainage kit is used.
Fluid Drainage:
Allow fluid to drain by gravity
If using a syringe and needle, aspirate fluid
If using a drainage kit, connect to a collection bag
Monitor fluid color, clarity, and volume
For therapeutic paracentesis exceeding 4-5 liters, consider intravenous albumin infusion (e.g., 6-8 g/L of drained fluid) to prevent circulatory compromise and re-expansion pulmonary edema.
Postoperative Care
Monitoring:
Closely monitor vital signs (BP, pulse, respiratory rate) for signs of hypovolemia or hypotension
Assess for abdominal pain, tenderness, or distension
Monitor urine output.
Fluid Replacement:
If large volumes of fluid (> 4-5 liters) are drained, administer intravenous albumin (6-8 g/L of drained ascites) to maintain intravascular volume and prevent circulatory dysfunction
Monitor for signs of fluid overload or overload.
Electrolyte Balance:
Monitor serum electrolytes, BUN, and creatinine post-procedure, especially in patients with significant fluid shifts or renal dysfunction
Correct any significant electrolyte abnormalities.
Antibiotic Prophylaxis:
Continue prophylactic antibiotics if indicated, particularly in patients with cirrhosis and a low SAAG, or those at high risk of SBP
For diagnostic paracentesis, administer antibiotics if SBP is suspected and before obtaining fluid cultures.
Dressing Care:
Apply a sterile dressing to the puncture site
Advise the patient to keep the site clean and dry and to report any signs of infection (redness, swelling, pus, fever) or fluid leakage.
Complications
Early Complications:
Hemorrhage (retroperitoneal or intra-abdominal)
Hypotension or hypovolemia
Re-expansion pulmonary edema
Infection (local site infection, SBP)
Bowel perforation (rare)
Vasovagal reaction
Leakage of ascitic fluid from the puncture site.
Late Complications:
Hernia formation at the puncture site (if large bore catheters are used repeatedly)
Chronic discomfort or pain
Persistent fluid leak.
Prevention Strategies:
Careful patient selection and exclusion of contraindications
Strict aseptic technique
Appropriate site selection
Judicious use of albumin infusion for large-volume paracentesis
Close monitoring of vital signs and fluid balance
Prompt recognition and management of complications.
Key Points
Exam Focus:
The SAAG is critical for differentiating between portal hypertension (SAAG ≥ 1.1 g/dL) and other causes of ascites (SAAG < 1.1 g/dL)
SBP diagnosis and management are high-yield
Albumin infusion protocols are essential for large-volume therapeutic paracentesis.
Clinical Pearls:
Always perform diagnostic paracentesis on new-onset ascites or if infection is suspected
Consider continuous drainage with a vacuum-assisted device for faster and more efficient fluid removal in therapeutic paracentesis
Monitor the patient closely for signs of circulatory collapse post-drainage.
Common Mistakes:
Performing paracentesis in patients with uncorrected coagulopathy
Inadequate local anesthesia leading to patient discomfort and movement
Failure to administer albumin with large-volume paracentesis, leading to hypovolemia
Misinterpreting ascitic fluid analysis or failing to send appropriate samples.