From the Guidelines
Paracentesis fluid analysis should include cell count with differential, albumin, total protein, culture, and glucose to diagnose conditions like spontaneous bacterial peritonitis (SBP), malignancy, or portal hypertension. The analysis of ascitic fluid obtained through paracentesis is crucial for diagnosing and managing various conditions. According to the most recent and highest quality study 1, a diagnostic paracentesis should be performed in all patients with new onset Grade 2 or 3 ascites, in all patients hospitalized for worsening of ascites, and in all patients with any complication of cirrhosis. The initial laboratory investigation of ascites fluid should include an ascitic fluid cell count and differential, ascitic fluid total protein, and albumin. Calculation of serum-ascites albumin gradient should be performed for differential diagnosis of ascites.
Essential Tests
- Cell count with differential
- Albumin
- Total protein
- Culture
- Glucose
For suspected SBP, fluid should be inoculated into blood culture bottles at the bedside to improve bacterial detection, as recommended by 1 and 1. The serum-ascites albumin gradient (SAAG) is crucial for differentiating between portal hypertension (SAAG ≥1.1 g/dL) and other causes like malignancy or infection (SAAG <1.1 g/dL). Additional tests may include lactate dehydrogenase, amylase, triglycerides, cytology, and tuberculosis studies depending on clinical suspicion.
Diagnosis of SBP
SBP is diagnosed when the neutrophil count exceeds 250 cells/mm³, requiring immediate antibiotic treatment, typically with a third-generation cephalosporin like ceftriaxone 1-2g IV daily for 5-7 days, as suggested by 1. For patients with cirrhosis, secondary prophylaxis with norfloxacin 400mg daily or trimethoprim-sulfamethoxazole is recommended after an SBP episode. The fluid's appearance can provide initial clues—clear yellow suggests uncomplicated cirrhosis, cloudy fluid indicates infection, bloody fluid suggests malignancy or tuberculosis, and milky fluid points to chylous ascites.
Key Recommendations
- Perform diagnostic paracentesis in all patients with new onset Grade 2 or 3 ascites, and in all patients hospitalized for worsening of ascites or any complication of cirrhosis 1
- Include cell count with differential, albumin, total protein, culture, and glucose in the initial laboratory investigation of ascites fluid 1
- Calculate serum-ascites albumin gradient for differential diagnosis of ascites 1
From the Research
Analysis of Ascitic Fluid
The analysis of ascitic fluid obtained through paracentesis is crucial in determining the cause of ascites and guiding treatment. The following parameters are typically included in the analysis:
- Serum ascites albumin gradient (SAAG)
- Total protein concentration
- Cell count and differential
- Optional tests such as cholesterol, fluid culture, cytology, tumor markers, lactate dehydrogenase, adenosine deaminase (ADA), triglyceride, amylase, glucose, and brain natriuretic peptide (BNP) 2
Diagnostic Algorithm
A diagnostic algorithm for patients with new-onset ascites has been established, which includes the evaluation of various parameters in ascitic fluid to determine the underlying etiology 2.
Spontaneous Bacterial Peritonitis (SBP)
SBP is a bacterial infection of ascitic fluid in patients with decompensated cirrhosis. The diagnosis of SBP is typically made by analyzing the ascitic fluid polymorphonuclear cell count, which is the most sensitive test for evaluating infection 3.
- The ascitic fluid analysis should include cell count and differential, albumin, glucose, gram stain, and culture
- Empirical therapy with antibiotics such as cefotaxime is recommended after paracentesis if suspicion for infection exists 3, 4
Organisms Causing SBP
The organisms causing SBP can vary, but common causes include:
- S. pneumoniae
- E. coli
- S. viridans
- K. pneumoniae
- H. influenza
- Enterococci
- Nontypable Streptococcus 4
Safety and Efficacy of Continuous Paracentesis
Continuous paracentesis via placement of an indwelling catheter can be safe and effective for the management of ascites, but it carries a risk of peritoneal infections 5.
- The risk of peritoneal infections increases if the peritoneal fluid is left in the abdomen for more than 3 days
- Regular monitoring of ascitic fluid culture and cell count is necessary to detect any potential infections 5