What is the recommended treatment for Peritoneal Dialysis (PD) peritonitis?

Diagnosis of Peritoneal Dialysis (PD) Peritonitis

PD peritonitis is diagnosed when at least 2 of 3 criteria are present: (1) cloudy dialysate effluent, (2) abdominal pain or tenderness, and (3) elevated white blood cell count in dialysate (>100 cells/mm³ with >50% polymorphonuclear cells). 1, 2

Diagnostic Criteria

Core Clinical Features

• Cloudy dialysate effluent is the most reliable single indicator and can be used as the sole criterion for initial diagnosis 1
• Abdominal pain or fever accompanies the cloudy effluent in most cases, though 10% of episodes may present with minimal symptoms 1
• Dialysate white blood cell count >100 × 10⁶/L with predominance of polymorphonuclear cells (>50%) confirms the diagnosis 1, 2

Important Diagnostic Caveats

• 10% of peritonitis episodes present with dialysate WBC <100 × 10⁶/L, so do not exclude peritonitis based solely on this threshold 1
• 15% of cases show initial mononuclear cell predominance rather than polymorphonuclear predominance, particularly in early presentations 1
• Between 9-31% of episodes would be missed if requiring all three diagnostic criteria simultaneously 1

Microbiologic Evaluation

Specimen Collection and Processing

• Obtain dialysate culture before initiating antibiotics by collecting effluent in blood culture bottles or using membrane filtration techniques 2
• Gram stain results are consistent with culture in only 28% of cases and should not delay empirical treatment 1
• Culture-negative peritonitis occurs in only 2% of cases when pre-culture membrane filtration is used 1

Advanced Diagnostic Techniques

• Mass spectrometry (MALDI-TOF) can identify fastidious or rare organisms that conventional biochemical assays miss, such as Capnocytophaga species 3
• Consider eosinophilic peritonitis when symptoms persist despite appropriate antibiotics, requiring specific cell differential analysis of dialysate (>90% eosinophils) 4

Critical Timing Considerations

All diagnostic testing must be performed when the patient is clinically stable and at least 1 month after resolution of any previous peritonitis episode 5, 6

• Peritonitis transiently increases peritoneal transport characteristics and causes impaired ultrafiltration with increased low-molecular-weight solute transport 5, 6
• These changes typically resolve within 1 month after peritonitis resolution, though recovery time ranges from 3 days to 1 month 5
• Testing performed during active peritonitis yields falsely elevated clearance measurements and unreliable peritoneal equilibration test (PET) results 6

Differential Diagnosis Considerations

Exit Site and Tunnel Infections

• Tunnel infection causes peritonitis more frequently with Staphylococcus aureus (p=0.009) compared to coagulase-negative staphylococci 1
• Examine the catheter exit site and tunnel carefully as these may be the source requiring catheter removal 2

Non-Infectious Causes

• Chemical peritonitis can occur from intraperitoneal vancomycin administration, presenting as cloudy dialysate with or without abdominal pain and fever 7
• Eosinophilic peritonitis may result from hypersensitivity to PD materials, dialysate components, or paradoxically from antibiotic therapy (especially vancomycin) 4

Common Pitfalls to Avoid

• Do not wait for culture results before initiating treatment - empirical antibiotics should begin immediately after specimen collection 2
• Do not rely on Gram stain alone - it influences initial therapy in only 7% of cases and has poor correlation with final culture 1
• Do not dismiss cloudy effluent in asymptomatic patients - turbidity alone warrants investigation and treatment 1
• Request specific eosinophil differential from the laboratory when peritonitis fails to respond to appropriate antibiotics, as this is not routinely reported 4