Peritonitis in Patients Undergoing Continuous Ambulatory Peritoneal Dialysis
المؤلف:
Longo, D., Fauci, A. S., Kasper, D. L., Hauser, S., Jameson, J. L., Loscalzo, J., Holland, S. M., & Langford, C. A.
المصدر:
Harrisons Principles of Internal Medicine (2025)
الجزء والصفحة:
22e , p1072
2025-09-07
255
A third type of peritonitis arises in patients who are undergoing continuous ambulatory peritoneal dialysis (CAPD). Unlike PBP and secondary peritonitis, which are caused by endogenous bacteria, CAPD-associated peritonitis usually involves skin organisms. The pathogenesis of infection is similar to that of intravascular device related infection, in which skin organisms migrate along the catheter, which both serves as an entry point and exerts the effects of a foreign body. Exit-site or tunnel infection may or may not accompany CAPD- associated peritonitis. Like PBP, CAPD-associated peritonitis is usually caused by a single organism. Peritonitis is, in fact, the most common reason for discontinuation of CAPD. Improvements in equipment design, especially the Y-set connector, have resulted in a decrease from one case of peritonitis per 9 months of CAPD to one case per 24 months. Diabetes was reported to be a risk factor for CAPD-associated peritonitis in a study from Taiwan.
The clinical presentation of CAPD peritonitis resembles that of secondary peritonitis in that diffuse pain and peritoneal signs are common. The dialysate is usually cloudy and contains >100 WBCs/μL, >50% of which are neutrophils. However, the number of cells depends in part on dwell time. According to a guideline from the International Society for Peritoneal Dialysis (2016), for patients undergoing automated peritoneal dialysis who present during their nighttime treatment and whose dwell time is much shorter than with CAPD, the clinician should use the percentage of PMNs rather than the absolute number of WBCs to diagnose peritonitis. As the normal peritoneum has very few PMNs, a proportion above 50% is strong evidence of peritonitis even if the absolute WBC count does not reach 100/μL. Meanwhile, patients undergoing automated peritoneal dialysis without a daytime exchange who present with abdominal pain may have no fluid to withdraw, in which case 1 L of dialysate should be infused and permitted to dwell a minimum of 1–2 h, then drained, examined for turbidity, and sent for cell count with differential and culture. The differential (with a shortened dwell time) may be more useful than the absolute WBC count. In equivocal cases or in patients with systemic or abdominal symptoms in whom the effluent appears clear, a second exchange is performed, with a dwell time of at least 2 h. Clinical judgment should guide initiation of therapy.
The most common organisms are Staphylococcus species, which accounted for ~45% of cases in one series. Historically, coagulase- negative staphylococcal species were identified most commonly in these infections, but these isolates have more recently been decreasing in frequency. Staphylococcus aureus is more often involved among patients who are nasal carriers of the organism than among those who are not, and this organism is the most common pathogen in overt exit site infections. Gram-negative bacilli and fungi such as Candida species also are found. Vancomycin-resistant enterococci and vancomycin- intermediate S. aureus have been reported to produce peritonitis in CAPD patients. The finding of more than one organism in dialysate culture should prompt evaluation for secondary peritonitis. As with PBP, culture of dialysate fluid in blood culture bottles improves the yield. To facilitate diagnosis, several hundred milliliters of removed dialysis fluid should be concentrated by centrifugation before culture.
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