What blood tests should be ordered in a patient recovering from peritonitis?

Blood Tests for Patients Recovering from Peritonitis

For patients recovering from peritonitis, blood tests should include complete blood count, comprehensive metabolic panel, inflammatory markers (C-reactive protein, procalcitonin), and blood cultures to monitor recovery and detect complications early. 1

Essential Blood Tests

Infection and Inflammatory Markers

• Complete blood count (CBC) with differential to monitor white blood cell count and neutrophil levels 1
• C-reactive protein (CRP) to track resolution of inflammation 1
• Procalcitonin (PCT) as a specific marker for bacterial infection and sepsis 1
• Blood cultures to identify persistent or new bacteremia 1

Renal Function Assessment

• Serum creatinine and blood urea nitrogen (BUN) to monitor kidney function and detect hepatorenal syndrome, a potential complication 1
• Serum electrolytes (sodium, potassium, chloride, bicarbonate) to detect imbalances that may occur during recovery 1

Liver Function Tests

• Liver enzymes (ALT, AST, alkaline phosphatase) to assess liver function, especially in cases of peritonitis secondary to cirrhosis 1
• Serum albumin and total protein to evaluate nutritional status and liver synthetic function 1
• Bilirubin (total and direct) to assess liver function 1

Metabolic Assessment

• Serum glucose to monitor for hyperglycemia, which can affect recovery 1
• Hemoglobin A1c in patients with suspected undiagnosed diabetes 1

Monitoring Schedule and Special Considerations

Frequency of Testing

• Daily monitoring of CBC, renal function, and electrolytes during acute recovery phase 1
• Every 2-3 days for inflammatory markers (CRP, PCT) to track resolution 1, 2
• Weekly liver function tests until clinical improvement is established 1

Special Considerations for Specific Types of Peritonitis

For Spontaneous Bacterial Peritonitis (SBP)

• Blood cultures should be performed before starting antibiotic treatment 1
• Systemic Immune Inflammation Index (SII), Neutrophil-Lymphocyte Ratio (NLR), and Platelet-Lymphocyte Ratio (PLR) can help predict culture positivity and prognosis 3
• Monitor for signs of hepatorenal syndrome with daily creatinine measurements 1

For Secondary Bacterial Peritonitis

• More frequent monitoring of inflammatory markers is recommended due to higher risk of persistent infection 1, 2
• Blood cultures should be repeated if clinical deterioration occurs 1, 4

Clinical Decision Points

When to Repeat Blood Tests More Frequently

• Persistent fever or signs of systemic inflammation 1
• Worsening abdominal pain or development of new symptoms 1, 2
• Deterioration in clinical status (e.g., development of shock, encephalopathy) 1
• Inadequate response to antibiotic therapy 1

When to Consider Additional Testing

• If thrombocytopenia develops (platelets <60 × 10^9/L), more intensive monitoring is needed as this is associated with higher mortality 5
• For patients with leukopenia (WBC <6 × 10^9/L), consider repeat blood cultures and antibiotic adjustment 5
• In patients with cirrhosis, monitor for development of hepatic encephalopathy with ammonia levels 1

Common Pitfalls to Avoid

• Failing to monitor renal function daily: Renal failure is a common complication and predictor of poor outcomes 1
• Overlooking electrolyte disturbances: These can develop rapidly during recovery and affect outcomes 1
• Discontinuing monitoring too early: Inflammatory markers may normalize before complete resolution of infection 2
• Neglecting to repeat blood cultures when clinical response is inadequate, which may indicate secondary peritonitis or antimicrobial resistance 1, 2
• Relying solely on WBC count without considering other inflammatory markers like CRP and procalcitonin 2, 6

By systematically monitoring these blood parameters, clinicians can effectively track recovery, detect complications early, and adjust treatment plans accordingly for patients recovering from peritonitis.