What is the differential diagnosis and treatment approach for peritonitis with lymphocytic predominance?

Peritonitis with Lymphocytic Predominance: Differential Diagnosis and Treatment

Tuberculous peritonitis is the primary diagnosis to consider when encountering lymphocytic-predominant ascites, particularly in high-risk patients from endemic areas, those with HIV/AIDS, or on immunosuppressive therapy. 1, 2

Differential Diagnosis

Primary Considerations

Tuberculous Peritonitis

• Lymphocytic ascites is the hallmark presentation, typically showing an exudative pattern with lymphocyte predominance 1, 2, 3
• Serum-ascites albumin gradient (SAAG) is characteristically <11 g/L 2
• Ascitic fluid total protein is elevated (exudative) 1
• Adenosine deaminase (ADA) levels >32-40 U/L have 100% sensitivity and 96.6-100% specificity in non-cirrhotic patients 1
• In cirrhotic patients with tuberculous peritonitis, use a lower ADA cutoff of 27 U/L (sensitivity 100%, specificity 93.3%) 1
• Acid-fast bacilli smear has poor sensitivity (0-86%), while culture sensitivity ranges 20-83% 1

Malignancy-Related Ascites (Peritoneal Carcinomatosis)

• Also presents with lymphocytic ascites 1
• Elevated CEA levels are highly specific for malignancy-related ascites 1
• Cytology has variable sensitivity but high specificity when positive 1
• SAAG typically <11 g/L 2

Secondary Considerations

Spontaneous Bacterial Peritonitis (SBP) - Atypical Presentation

• Classic SBP shows neutrophil predominance (>250/mm³), not lymphocytic 1
• Typically monomicrobial with gram-negative organisms (60%), most commonly E. coli 1, 4
• If lymphocytes predominate, SBP is unlikely unless very early or resolving 1

Secondary Bacterial Peritonitis

• Should be suspected with multiple organisms on culture, very high neutrophil count, high ascitic protein, or inadequate response to therapy 1
• Ascitic glucose <50 mg/dL and LDH higher than serum LDH suggest secondary peritonitis 1
• Elevated CEA (>5 ng/mL) or alkaline phosphatase (>240 U/L) support perforated viscus 1

Diagnostic Algorithm

Immediate Steps

1. Perform diagnostic paracentesis urgently in all patients with new ascites or clinical deterioration 1

   • Send for cell count with differential, total protein, albumin, glucose, LDH 1
   • Inoculate ≥10 mL into blood culture bottles at bedside before antibiotics 1
   • Obtain simultaneous blood cultures 1

2. Calculate SAAG to differentiate portal hypertension (≥11 g/L) from other causes (<11 g/L) 2

3. For lymphocytic ascites with SAAG <11 g/L:

   • Order ADA level (cutoff 32-40 U/L in non-cirrhotic; 27 U/L in cirrhotic patients) 1
   • Send AFB smear and mycobacterial culture 1
   • Order ascitic CEA if malignancy suspected 1
   • Send cytology for malignant cells 1

Advanced Diagnostic Measures

When Initial Tests Are Inconclusive:

• Laparoscopy with peritoneal biopsy is the gold standard for tuberculous peritonitis, allowing direct visualization and tissue diagnosis 1, 2, 3
• PCR testing for mycobacteria accelerates diagnosis 1, 2
• CT or ultrasound-guided peritoneal biopsy as alternative 2, 3

High-Risk Populations Requiring Mycobacterial Testing:

• Recent immigration from TB-endemic areas 1
• HIV/AIDS patients 2
• Patients on immunosuppressive therapy 2
• End-stage renal or liver disease 2, 5

Treatment Approach

Tuberculous Peritonitis

Initiate empiric anti-tuberculous therapy immediately if clinical suspicion is high, as mortality is substantial (up to 52% in some series) with most deaths occurring within 6 weeks before culture results return 5

• Standard 6-month regimen with first-line agents: isoniazid, rifampicin, ethambutol, and pyrazinamide 2, 3
• Do not wait for culture confirmation in high-risk patients with compatible clinical picture 5
• Laparoscopy should have a low threshold for definitive diagnosis 2

Malignancy-Related Ascites

• Treatment directed at underlying malignancy 1
• Therapeutic paracentesis for symptomatic relief 1
• Systemic chemotherapy based on primary tumor type 1

If SBP Cannot Be Excluded

• Third-generation cephalosporins (cefotaxime 2g IV every 8 hours) remain first-line for suspected SBP 1, 4
• Albumin infusion (1.5 g/kg at diagnosis, 1 g/kg on day 3) reduces renal failure and mortality in SBP 6
• Repeat paracentesis at 48 hours to document decreasing neutrophil count 1

Critical Pitfalls to Avoid

• Do not delay anti-tuberculous therapy while awaiting culture results in high-risk patients with lymphocytic ascites and elevated ADA—mortality increases dramatically with delayed treatment 5
• Do not rely solely on AFB smear (sensitivity 0-86%)—negative smear does not exclude tuberculosis 1
• Do not use standard ADA cutoffs in cirrhotic patients—lower threshold (27 U/L) is required 1
• Do not miss secondary peritonitis—multiple organisms, very high neutrophils, or glucose <50 mg/dL mandate CT imaging and surgical evaluation 1
• Perform CT scan promptly if secondary peritonitis suspected to identify surgically correctable source 1