Case 10: Additional Diagnostic Testing

Case 10 Index

You’ve obtained a sample of the peritoneal dialysis fluid from this patient’s abdomen. What do you want to do next (more than one answer choice may be correct)?
Send the fluid to the lab for cell count and differential
Correct! An elevated dialysate white blood cell (WBC) count >100 cells/microL and/or greater than 50% polymorphonuclear leukocytes (PMNs) would be consistent with bacterial peritonitis.
 Send the fluid to check creatinine levels
This test is unlikely to give us information to help diagnose this patient’s abdominal pain. Try again!
Send the fluid for bacterial culture and gram stain
Absolutely, these tests are crucial and should be sent as soon as possible (ideally before antibiotic therapy).
Send the fluid for fungal culture
Fungal peritonitis is far less common than bacterial peritonitis in patients on PD, but it carries higher morbidity and mortality. This culture is not routinely sent unless suspicion for fungal infection is high or a patient has had culture negative peritonitis for several days.
 Send the fluid for triglyceride levels
This test is performed to assess for chylous ascites, for which we have low suspicion in this case. Try again!


The peritoneal fluid cell count and differential come back:

WBC 220/microL
PMN 66%

What is the best next step?
Start intraperitoneal vancomycin and gentamicin
Correct! Direct delivery of antibiotics to the peritoneal space is ideal, and vancomycin plus gentamicin provides good gram-positive and gram-negative coverage empirically.
 Start intravenous vancomycin and gentamicin
While this is an option if intraperitoneal antibiotics are unavailable, direct delivery to the peritoneal space is the best approach.
Start intraperitoneal vancomycin
Broad empiric gram-positive and gram-negative coverage should be initiated until gram stain and/or culture results have returned. Vancomycin will provide gram-positive coverage, but an additional agent should be given to cover gram-negative organisms. Try again!
Await the gram stain results before initiating antibiotics
Peritonitis is a serious infection, and time to antibiotic delivery is crucial. Empiric coverage should be started. Try again!
Remove the peritoneal dialysis catheter
A single episode of peritonitis with a suspected bacterial infection is not an indication to remove a PD catheter. Try again!

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Case 10 Index
Case 10 Introduction
Case 10 Physical Exam
Case 10 Diagnostic Testing