Should Ascitic Tap Be Done in SBP?
Yes, diagnostic paracentesis must be performed immediately in all patients with cirrhosis and ascites at hospital admission to diagnose SBP, and should be repeated urgently in any patient who develops signs of infection or clinical deterioration. 1
When to Perform Diagnostic Paracentesis
At Hospital Admission
- All cirrhotic patients with ascites require diagnostic paracentesis upon hospital admission, regardless of symptoms. 1
- This is a Class I, Level A/B recommendation across all major hepatology guidelines. 1
- SBP is frequently asymptomatic or presents with minimal symptoms, making clinical criteria unreliable for excluding infection. 2
Urgent Indications for Paracentesis
Perform diagnostic tap immediately in patients with any of the following: 1
- Fever (temperature >100°F or <96.8°F)
- Abdominal pain or tenderness
- Hepatic encephalopathy (new or worsening)
- Gastrointestinal bleeding
- Shock or hemodynamic instability
- Renal failure or rising creatinine
- Worsening liver function (rising bilirubin, INR)
- Acidosis
- Peripheral leukocytosis
Diagnostic Criteria
Making the Diagnosis
- SBP is diagnosed when ascitic fluid polymorphonuclear (PMN) count is ≥250 cells/mm³, regardless of culture results. 1
- Culture positivity occurs in only 50-80% of cases, even with optimal bedside inoculation into blood culture bottles. 1, 3
- Culture-negative neutrocytic ascites (PMN ≥250/mm³ with negative culture) should be treated identically to culture-positive SBP. 1, 3
Specimen Collection
- Obtain at least 10 mL of ascitic fluid. 4
- Inoculate blood culture bottles at bedside before starting antibiotics to maximize culture yield. 1, 4
- Send fluid for: cell count with differential, culture, total protein, and additional tests as clinically indicated. 1
Follow-Up Paracentesis
When Repeat Tap is Indicated
- Perform repeat paracentesis 48 hours after initiating antibiotics to assess treatment response. 4
- Treatment failure is defined as <25% decrease in PMN count from baseline. 4
- Repeat tap is essential when: 1
- Clinical presentation is atypical
- Multiple organisms are cultured (suggests secondary peritonitis)
- Patient fails to improve clinically within 48 hours
- Very high PMN count (>1,000/mm³) raises concern for secondary peritonitis
When Follow-Up Tap is Not Needed
- Most patients with typical SBP do not require follow-up paracentesis if they demonstrate dramatic clinical improvement. 1
- Typical features include: advanced cirrhosis, typical symptoms, ascitic protein <1 g/dL, single organism on culture, and rapid clinical response. 1
Critical Pitfalls to Avoid
Clinical Presentation Cannot Exclude SBP
- Up to 7-13% of SBP cases are completely asymptomatic. 2
- Clinical criteria (fever, abdominal pain) have very low sensitivity and specificity for SBP diagnosis. 2
- Relying on symptoms alone will miss a substantial proportion of cases, leading to increased mortality. 2
Distinguishing Secondary Peritonitis
Secondary bacterial peritonitis should be suspected when: 1
- Multiple organisms are present on culture or Gram stain
- Very high PMN count (often >1,000/mm³)
- Localized abdominal symptoms or peritoneal signs
- Inadequate response to appropriate antibiotics within 48 hours
- High ascitic protein concentration
Patients with suspected secondary peritonitis require urgent CT imaging and surgical consultation. 1, 3
Timing is Critical
- Delaying antibiotic therapy increases mortality by approximately 10% for every hour's delay in patients with septic shock. 3
- Start empiric antibiotics immediately after obtaining ascitic fluid, without waiting for culture results. 1, 4, 3
Treatment Initiation
Empiric Antibiotic Therapy
- Third-generation cephalosporin (cefotaxime 2g IV every 8-12 hours or ceftriaxone) is first-line for community-acquired SBP. 1, 4
- For nosocomial or healthcare-associated SBP, use broad-spectrum coverage (carbapenem or piperacillin-tazobactam). 4, 5