Ann Lab Med 2020; 40(3): 238-244  https://doi.org/10.3343/alm.2020.40.3.238
Prevalence and Clinical Characteristics of Asymptomatic Pyuria in Chronic Kidney Disease
Young Eun Kwon, M.D., Ph.D.1,*, Dong-Jin Oh, M.D., Ph.D.1,*, Moon Jung Kim, M.D., Ph.D.2, and Hye Min Choi, M.D., Ph.D.1
1Department of Internal Medicine, Myongji Hospital, Hanyang University College of Medicine, Goyang, Korea; 2Department of Laboratory Medicine, Myongji Hospital, Hanyang University College of Medicine, Goyang, Korea
Corresponding author: Hye Min Choi, M.D., Ph.D.
Division of Nephrology, Department of Internal Medicine, Myongji Hospital, Hanyang University College of Medicine, 55 Hwasu-ro 14beon-gil, Deogyang-gu, Goyang 10475, Korea
Tel: +82-31-810-6030 Fax: +82-31-969-0500 E-mail: ltriver@hanmail.net

* These authors equally contributed to this study.
Received: March 15, 2019; Revised: July 3, 2019; Accepted: November 18, 2019; Published online: May 1, 2020.
© Korean Society for Laboratory Medicine. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background: Pyuria seems to be common in chronic kidney disease (CKD), irrespective of urinary tract infection (UTI). It has been hypothesized that sterile pyuria occurs in CKD because of chronic renal parenchymal inflammation. However, there are limited data on whether CKD increases the rate of pyuria or how pyuria in CKD should be interpreted. We investigated the prevalence and characteristics of asymptomatic pyuria (ASP) in CKD via urinary white blood cell (WBC) analysis.
Methods: Urine examination was performed for all stable hemodialysis (HD) and non-dialysis CKD patients of the outpatient clinic (total N=298). Patients with infection symptoms or recent history of antibiotic use were excluded. Urine culture and WBC analysis were performed when urinalysis revealed pyuria.
Results: The prevalence of ASP was 30.5% (24.1% in non-dialysis CKD and 51.4% in HD patients). Over 70% of the pyuria cases were sterile. The majority of urinary WBCs were neutrophils, even in sterile pyuria. However, the percentage of neutrophils was significantly lower in sterile pyuria. In multivariate logistic regression analysis, the degree of pyuria, percentage of neutrophils, and presence of urinary nitrites remained independently associated with sterile pyuria.
Conclusions: The prevalence of ASP was higher in CKD patients and increased according to CKD stage. Most ASP in CKD was sterile. Ascertaining the number and distribution of urinary WBCs may be helpful for interpreting ASP in CKD.
Keywords: Asymptomatic pyuria, Chronic kidney disease, Cellular analysis, Prevalence, Sterile, Neutrophil



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