Ann Lab Med.  2020 May;40(3):238-244. 10.3343/alm.2020.40.3.238.

Prevalence and Clinical Characteristics of Asymptomatic Pyuria in Chronic Kidney Disease

• Kwon YE
• Oh DJ
• Kim MJ
• Choi HM

• KMID: 2466017
• DOI: http://doi.org/10.3343/alm.2020.40.3.238

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.

Keyword

Asymptomatic pyuria; Chronic kidney disease; Cellular analysis; Prevalence; Sterile; Neutrophil

MeSH Terms

Ambulatory Care Facilities
Humans
Inflammation
Leukocytes
Logistic Models
Neutrophils
Nitrites
Prevalence*
Pyuria*
Renal Dialysis
Renal Insufficiency, Chronic*
Urinalysis
Urinary Tract Infections
Viperidae
Nitrites

Figure

• 

  Fig. 1 The prevalence of pyuria according to the level of renal function. The prevalence of pyuria was investigated in asymptomatic CKD population. CKD was divided into HD and non-dialysis CKD; non-dialysis CKD was further classified as stages 3, 4, and 5 according to the KDIGO classification [11]. The prevalence of pyuria in the non-CKD population was estimated from regular health examination data at the study hospital and included control patients aged >40 years with eGFR ≥60 mL/min/1.73 m2.Abbreviations: CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; HD, hemodialysis; KDIGO, Kidney Disease Improving Global Outcomes.

• 

  Fig. 2 ROC curves showing the effectiveness of the number and distribution of urinary WBCs in UTI identification. The number of WBCs was analyzed at different cut-off values: ≥10, ≥20, and ≥50 WBCs/HPF.Abbreviations: ROC, receiver operating characteristic; UTI, urinary tract infection; WBC, white blood cells; HPF, high-power field.

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