CAPD Peritonitis: Diagnostic Criteria and Treatment
Peritonitis in CAPD is diagnosed when at least 2 of 3 criteria are present: (1) clinical symptoms of peritoneal irritation (abdominal pain/tenderness), (2) cloudy dialysate effluent with white blood cell count >100/μL with >50% polymorphonuclear cells, and (3) positive dialysate culture. 1
Diagnostic Criteria
The diagnosis does not require all three criteria to be met simultaneously. Key diagnostic considerations include:
- Cloudy effluent is typically the earliest and most reliable sign, though 10% of peritonitis episodes may initially present with clear effluent and WBC <100/μL 2
- Clinical symptoms alone can precede cloudy fluid by 7-12 hours in some cases, particularly with acute presentations mimicking surgical abdomen 3
- Culture results take time but should be positive in 98% of cases when proper techniques (membrane filtration) are used 2
- Gram stain has limited utility, being consistent with culture in only 28% of episodes and rarely influencing initial therapy 2
Important Diagnostic Pitfall
Do not delay treatment waiting for all three criteria or culture results. If a patient presents with abdominal pain and clear effluent, repeat the dialysate examination within 12 hours—the effluent will typically become turbid with elevated WBC counts 3. Between 9-31% of peritonitis episodes would be missed if all three criteria were required 2.
Treatment Approach
Empirical Antibiotic Therapy
Initial empirical treatment should cover both gram-positive and gram-negative organisms using intraperitoneal administration. The 2022 ISPD guidelines recommend 1:
Primary regimen:
- Vancomycin (gram-positive coverage) PLUS
- Ceftazidime or cefepime (gram-negative coverage including Pseudomonas)
Dosing for vancomycin: Intermittent dosing of 15-30 mg/kg IP in one exchange per week (preferred over continuous dosing for convenience and equivalent efficacy) 4
Avoid Aminoglycosides When Possible
While historically used, aminoglycosides should be avoided as first-line therapy because:
- They are nephrotoxic and accelerate loss of residual kidney function 5
- Residual kidney function is critically important for patient survival (more so than peritoneal clearance) 5
- Alternative regimens (vancomycin + ceftazidime) are equally effective without this toxicity 4
If aminoglycosides must be used, consider adjunctive oral N-acetylcysteine to mitigate ototoxicity 1
Organism-Specific Modifications
Once culture results return, tailor therapy accordingly:
- Coagulase-negative staphylococci: Generally milder course with better outcomes 2
- Staphylococcus aureus: Higher association with tunnel infections; evaluate catheter exit site 2
- Pseudomonas aeruginosa: Often requires catheter removal for cure 6
- Fungal peritonitis: Requires immediate catheter removal 6
- Enteric organisms: Evaluate for bowel perforation or intra-abdominal pathology 1
Treatment Duration and Monitoring
- Continue antibiotics for 14-21 days depending on organism
- Monitor dialysate cell counts at 48-72 hours to assess response
- Refractory peritonitis (failure to improve after 5 days of appropriate antibiotics) requires catheter removal 1
Quality Benchmarks
Target peritonitis rate should be ≤0.40 episodes per year at risk, with >80% of patients remaining peritonitis-free annually 1. Programs should track and report these metrics as part of quality improvement.
Critical Considerations for Residual Kidney Function
Given that residual kidney function is the most important predictor of survival in PD patients 5:
- Avoid nephrotoxic antibiotics (aminoglycosides, NSAIDs including COX-2 inhibitors) whenever possible 5
- Ensure adequate hydration during peritonitis treatment
- Consider ACE inhibitors or ARBs to preserve residual function, even in normotensive patients 5
- Each peritonitis episode accelerates loss of residual function 5