Dwell Time for PD Fluid Collection in Suspected Peritonitis
In suspected peritoneal dialysis-associated peritonitis, peritoneal fluid should be collected immediately upon presentation without requiring any specific dwell time, as prompt diagnosis and treatment are essential for reducing morbidity and mortality. 1
Collection Process for PD Fluid in Suspected Peritonitis
Immediate Collection
- Collect peritoneal fluid samples as soon as peritonitis is suspected
- No need to wait for a specific dwell time before drainage
- Prompt collection is critical for early diagnosis and treatment initiation
Sample Processing
- Use the "aliquot method" for sample collection:
- Shake each bag of effluent dialysate vigorously for a few seconds
- Empty into a measuring container (accurate to within 50 mL per 2,000 mL)
- Record the volume in mL
- Take appropriate sample volume for laboratory testing 2
Culture Techniques to Maximize Yield
- Direct inoculation of peritoneal fluid into automated blood culture bottles is recommended as it:
- Significantly increases positivity rates (87% vs 53% with conventional methods)
- Aids in early detection of causative organisms 3
- Consider multiple culture methods when possible to maximize pathogen identification
Diagnostic Criteria and Interpretation
White Blood Cell Count Thresholds
- Traditional diagnostic threshold: >100 WBC/μL with >50% neutrophils
- Recent evidence suggests a higher threshold of 230 WBC/μL may improve specificity (89%) without compromising sensitivity (99.8%) 4
- Consider clinical presentation alongside cell counts for diagnosis
Timing Considerations for Follow-up Measurements
- All measurements of peritoneal solute clearance should be obtained:
- When the patient is clinically stable
- At least 1 month after resolution of peritonitis
- Peritonitis transiently changes the patient to a high transporter and decreases ultrafiltration 2
Important Clinical Considerations
Impact on Membrane Function
- Peritonitis causes temporary changes in peritoneal transport characteristics:
- Increases peritoneal transport of low-molecular-weight solutes
- Increases rates of glucose absorption
- Decreases ultrafiltration capacity
- These changes typically resolve within 1 month after peritonitis resolution 2
Pitfalls to Avoid
- Do not delay collection for a specific dwell time - this may delay diagnosis and treatment
- Avoid aminoglycosides if equally effective alternatives exist to preserve residual renal function 1
- Be aware that peritonitis episodes are associated with more rapid decline in residual renal function 1
- Do not perform peritoneal membrane function testing during or immediately after peritonitis episodes, as results will be inaccurate 2
By following these guidelines, clinicians can optimize the diagnosis and management of peritoneal dialysis-associated peritonitis, potentially improving patient outcomes by enabling prompt and appropriate treatment.