Sterile pyuria: a differential diagnosis

Urinary Tract Infections in Children

Despite the American Academy of Pediatrics guidelines for the evaluation, treatment, and management of urinary tract infections (UTIs), UTI diagnosis and management remains challenging for clinicians. Challenges with acute UTI management stem from vague presenting signs and symptoms, diagnostic uncertainty, limitations in laboratory testing, and selecting appropriate antibiotic therapy in an era with increasing rates of antibiotic-resistant uropathogens. Recurrent UTI management remains difficult due to an incomplete understanding of the factors contributing to UTI, when to assess a child with repeated infections for kidney and urinary tract anomalies, and limited prevention strategies. To help reduce these uncertainties, this review provides a comprehensive overview of UTI epidemiology, risk factors, diagnosis, treatment, and prevention strategies that may help pediatricians overcome the challenges associated with acute and recurrent UTI management.

Diagnostic Value of Urine Ribonuclease 7 (RNase 7) to Creatinine Ratio for Detecting Urinary Tract Infection in Children with Pyuria

Objective Ribonuclease 7 (RNase 7) is one of the members of the antimicrobial peptides playing a role in maintaining urinary tract sterility. We aimed to investigate the predictive value of the urine RNase 7 levels in children with pyuria and associations between RNase 7 and vesicoureteral reflux (VUR) and renal scarring.

Methods This study included 109 children with pyuria (46 febrile urinary tract infections [UTIs], 38 nonfebrile UTIs, and 25 sterile pyuria) whose RNase 7 levels were measured by enzyme-linked immunoassay. The results for urine RNase 7 concentrations were expressed as micrograms per milligrams creatinine.

Results RNase 7/Cr levels were higher in patients with both febrile and nonfebrile UTIs than the patients with sterile pyuria (p = 0.001). RNase 7/Cr had predictive values of diagnosis of febrile and nonfebrile UTIs (cut-off value: 2.92 µg/mg, p = 0.003; cut-off value: 3.67 µg/mg, p < 0.001, respectively). RNase 7/Cr had higher levels in the patients with VUR than without VUR (cut-off value: 4.28 µg/mg, p = 0.037). The patients with renal scarring had higher urine RNase 7/Cr than those without scarring (cut-off value: 4.54 µg/mg, p = 0.041).

Conclusion The evaluation of RNase 7/Cr may help prevent unnecessary and/or inappropriate antibiotic use in children with pyuria. The higher RNase 7 levels in patients with VUR and renal scarring may reflect long-term inflammation or greater inflammatory response during acute infection.

The Differential Diagnosis of Sterile Pyuria in Pediatric Patients: A Review

Sterile pyuria is a common finding in pediatric patients. Literature describing the diagnoses as well as clinical characteristics of children with sterile pyuria is lacking. This review was performed to establish an evidence-based approach to the differential diagnosis by way of an extensive literature search. The definition of pyuria is inconsistent. The various causes of pediatric sterile pyuria identified were classified as either Infectious or Non-Infectious. Sub-categories of Infectious causes include: Viral Infection, Bacterial Infection, Other Infections (tuberculosis, fungal, parasitic), Sexually Transmitted Infections, Recent Antibiotic Therapy. Non-Infectious causes include: Systemic Disease, Renal Disease, Drug Related, Inflammation adjacent to Genitourinary Tract. Clinicians that encounter pediatric patients with sterile pyuria and persistent symptoms should consider the substantial differential diagnosis described in this study.

Impact of sterile leukocyturia on outcome of critically ill patients with severe acute kidney injury

INTRODUCTION

The role of immunological mechanisms on renal regeneration and functional recovery after an episode of Acute Kidney Injury (AKI) is still understudied. We aim to evaluate the impact of sterile leukocyturia on outcomes of critically-ill AKI patients.

METHODS

A retrospective analysis of critically-ill patients with stage ≥2 AKI by KDIGO was performed. Patients with urinary tract infection, previous renal replacement therapy, chronic kidney disease stage >3 and kidney, urinary tract or prostatic cancer were excluded. Sterile leukocyturia was defined as a positive leukocyte esterase value.

RESULTS

108 patients with stage ≥2 AKI were included, 39.8% of which had sterile leukocyturia. AKI patients with sterile leukocyturia were older, had more cardiovascular disease and a lower baseline renal function (p < 0.05). They had a higher serum creatinine and leukocytosis at admission, were more frequently septic (p < 0.05) and had more persistent AKI by both KDIGO criteria at multivariable analysis (OR 6.130, 95% CI 2.007-18.747).

CONCLUSION

Sterile leukocyturia was associated with different patient baseline and AKI characteristics and more persistent AKI by both KDIGO criteria. Sterile leukocyturia may represent a surrogate marker of renal inflammation during AKI.

Pyuria, urinary tract infection and renal outcome in patients with chronic kidney disease stage 3-5

Pyuria is common in chronic kidney disease (CKD), which could be due to either urinary tract infection (UTI) or renal parenchymal inflammation. Only little is known regarding the association of pyuria or UTI with renal outcomes. We investigated 3226 patients with stage 3–5 CKD. Pyuria was defined as ≥ 50 WBC per high-power field (hpf) and was correlated to old age, female, diabetes, hypoalbuminemia, lower eGFR, and higher inflammation status. In Cox regression, patients with more than one episode of pyuria in the first year (11.8%) had increased risks for end-stage renal disease (ESRD) [hazard ratio (95% CI): 1.90 (1.58–2.28); p < 0.001], rapid renal function progression [odds ratio (95% CI): 1.49 (1.13–1.95); p = 0.001], and all-cause mortality [hazard ratio: 1.63 (1.29–2.05); p < 0.001], compared to those without pyuria. In a subgroup analysis, the risk of pyuria for ESRD was modified by CKD stages. We investigated the effects of UTI (urinary symptoms and treated by antibiotics) and pyuria without UTI (urine WBC < 50 to ≥ 10/hpf without any episodes of ≥ 50 WBC/hpf or UTI), while both groups were associated with clinical outcomes. In conclusion, CKD stage 3–5 patients with frequent pyuria or UTI episodes have increased risks of renal outcomes.

How Sensitive are Dipstick Urinalysis and Microscopy in Making Diagnosis of Urinary Tract Infection in Children?

Background

Urinary tract infection (UTI) is a common reason for referral to the emergency department (ED) especially in unwell infants. Upper UTIs are particularly at risk of significant complications later in life. Rapid dipstick urinalysis and microscopy are often used in unwell children as a screening tool to guide early diagnosis and treatment. This study aims to evaluate the sensitivity of dipstick urinalysis and microscopy in the diagnosis of UTI.

Methods

A retrospective review of children aged 16 years and below with positive urine culture (UC) over a 3-year period was done. The results of urine dipstick and microscopy were compared with the positive UC and sensitivities calculated.

Results

Dipstick urinalysis and microscopy of 262 children were studied. Female-to -male ratio of 1.8:1. Median age was 0.79 (range: 0.02-15.95) years. The sensitivity of nitrite, blood, and leukocyte esterase (LE) were 0.54, 0.74, and 0.86 (95% confidence interval [CI] = 0.46-0.62, 0.68-0.80, and 0.82-0.91), respectively. The sensitivity of pyuria of ≥100 cells/mm³ was 0.92 (95% CI = 0.89-0.95). The presence of any of the 3 dipstick parameters increased the sensitivity to 0.97 (95% CI = 0.95-0.99). The lowest sensitivity 0.49 (95% CI = 0.40-0.58) was found with combined positive LE and nitrite. There was a significant comparison between positive LE dipstick test and pyuria (P = 0.000004).

Conclusions

Dipstick urinalysis may not be reliable in ruling out UTI in children. However, considering both positive dipstick and pyuria will be more useful in making the diagnosis.

The Emergency Department Diagnosis and Management of Urinary Tract Infection

Urinary tract infection (UTI) is a common infection seen in the emergency department. The spectrum of UTI includes simple versus complicated infection and lower versus upper UTI. No one history or examination finding is definitive for diagnosis. Testing often includes urinalysis and/or urine dipstick, and several pitfalls may occur in interpretation. Urine cultures should be obtained in complicated or upper UTIs but not simple and lower tract UTIs, unless a patient is pregnant. Imaging often is not required. Most patients with simple cystitis and pyelonephritis are treated as outpatients. A variety of potentially dangerous conditions may mimic UTI and pyelonephritis.

Results of Real-time Multiplex Polymerase Chain Reaction Assay in Renal Transplant Recipients With Sterile Pyuria

Urinary tract infections are a major cause of morbidity and hospitalization after renal transplantation. Patients treated with immunosuppressive drugs suffer not only from common uropathogens but also from opportunistic infections caused by unusual uropathogens. Sterile pyuria is associated with numerous infectious agents including viruses, fungi, and atypical or fastidious organisms. The objective of this study was to investigate the pathogens using real-time multiplex polymerase chain reaction (rtMPCR) assay in sterile pyuria of renal transplant recipients. In this prospective controlled study, pathogen detection was performed with rtMPCR assay on October 2016 in 60 patients with sterile pyuria who had undergone kidney transplantation. A total of 40 renal transplant patients were determined as the control group. Male-to-female ratio was same. The mean age of the subjects with sterile pyuria was 45.7 ± 12.1 (25-74). The mean duration after transplantation was 28.8 ± 3.97 (3-102) months. Pathogens were detected with rtMPCR in 61.7% of sterile pyuria group. This rate was significantly higher compared with the control group (P < .001). Two or more different pathogens were found in 13 (21.7%) patients in sterile pyuria group. The pathogens found included cytomegalovirus in 10 patients (19%), Gardnerella vaginalis and obligate anaerobes in 20 patients (38%), Ureaplasma spp in 17 patients (33%), Candida spp in 2 patients (4%), Mycoplasma hominis in one patient (2%), herpes simplex virus-2 in one patient (2%), and Trichomonas vaginalis in one patient (2%). Sterile pyuria may indicate the presence of genitourinary pathogens that cannot be detected with conventional urine culture method in renal transplantation patients. rtMPCR is an accurate and convenient method for detection of multiple potential pathogens of sterile pyuria in renal transplant patients.

Urinary Tract Infection and Antimicrobial Stewardship in the Emergency Department

OBJECTIVES

The aims of this study were to assess empiric antibiotic use for presumed urinary tract infection (UTI) in the emergency department (ED) and to determine how often urine culture results subsequently do not confirm the diagnosis.

METHODS

This study is a retrospective cohort study of patients aged 21 years or younger in the Nationwide Children's Hospital ED from May 1, 2012, to October 31, 2012, who had a urinalysis and urine culture performed and were discharged home with empiric antibiotic therapy for presumed UTI. Patients with known urinary tract anomaly or antibiotic use in the previous 7 days were excluded. Confirmed UTI was defined as pyuria (>5 white blood cells per high-power field or dipstick positive for leukocyte esterase) and a positive urine culture (≥50,000 colony-forming units/mL of a uropathogen).

RESULTS

Of the 175 enrolled patients, urine was obtained by clean catch in 138 (79%), catheterization in 35 (20%), first-pass void in 1 (0.6%), and undocumented method in 1 (0.6%). Pyuria was demonstrated in 164 patients (94%), but only 97 (55%) had a positive urine culture. The combination of pyuria and a positive urine culture confirmed UTI in 90 patients (51%). The most commonly prescribed antibiotics were cefdinir in 103 patients (59%), trimethoprim/sulfamethoxazole in 40 (23%), and ciprofloxacin in 23 (13%). The median duration of prescribed therapy was 10 days (interquartile range, 7-10 days). Treatment duration was correlated negatively with age (r = -0.53, P < 0.01).

CONCLUSIONS

The current management of suspected UTI in ED patients results in unnecessary antibiotic exposure, highlighting an important opportunity for outpatient antimicrobial stewardship efforts.

A case of sterile pyuria caused by Chlamydia trachomatis and Mycoplasma hominis: A diagnostic challenge

Sterile pyuria is a highly prevalent condition with a wide aetiological spectrum, which often challenges the diagnostician. We describe the case of a middle-aged female admitted to the medical Intensive Care Unit for acute gastroenteritis, whose urinalysis revealed persistent sterile pyuria. Polymerase chain reaction assay in urine was positive for Chlamydia trachomatis and Mycoplasma hominis. She responded to antimicrobial therapy. We hereby reflect on the approach to a case of sterile pyuria and review the available literature on this entity.

Differentiation of acute pyelonephritis from other febrile states in children using urinary neutrophil gelatinase-associated lipocalin (uNGAL)

BACKGROUND

Acute pyelonephritis is a severe disease which is sometimes difficult to recognize based on clinical symptoms and routinely available diagnostic tests, especially in young children. The aim of this study was to assess the diagnostic value of urinary neutrophil gelatinase-associated lipocalin (uNGAL) as a biomarker of acute pyelonephritis.

METHODS

In this case-control study we analyzed 134 children (median age 2.5 years) who were admitted to the Pediatric Clinic of University Hospital Centre Osijek, Croatia. Eighty of them had acute pyelonephritis, while 54 children had febrile state of different etiology including cystitis and they represented the control group. uNGAL, white blood cells, C-reactive protein, urinanalysis, urine culture, kidney ultrasound and a dimercaptosuccinic acid scintigraphic scan were done for each child. uNGAL was measured using chemiluminiscent microparticle immunoassay on ARHITECT i1000SR (Abbott Diagnostics, IL, USA).

RESULTS

uNGAL values were significantly higher in children with acute pyelonephritis compared to the control groups (113.6 ng/mL vs. 10.2 ng/mL, p<0.001). A receiver operating characteristic curve comparison was done for tested parameters and encouraging results were obtained for uNGAL (AUC=0.952). A cut-off value of 29.4 ng/mL had 92.5% sensitivity and 90.7% specificity. We showed that uNGAL can also serve in differentiating acute pyelonephritis from cystitis (cut-off 38.5 ng/mL), and for differentiation of cystitis from febrile states with etiology other than urinary tract infection (UTI) (cut-off 20.4 ng/mL).

CONCLUSIONS

uNGAL can be a useful diagnostic biomarker in acute pyelonephritis in children, but also in differentiating cystitis from febrile states other than UTI.

Evaluation of novel urinary tract infection biomarkers in children

BACKGROUND

Pediatricians frequently use urinalysis to diagnose urinary tract infection (UTI) while awaiting urine culture results, but sensitivity and specificity of urinalysis are limited. This study evaluated the diagnostic accuracy of the antimicrobial peptides (AMPs) human α-defensin 5 (HD5) and human neutrophil peptides (HNP) 1-3 as novel UTI biomarkers in children.

METHODS

We prospectively enrolled 199 pediatric Emergency Department or Urgent Care patients evaluated for a UTI. Urine concentrations of HD5 and HNP1-3 were measured by enzyme-linked immunosorbent assay. Urine culture was the reference standard. Sensitivities and specificities of leukocyte esterase (LE), HD5, HNP1-3, and test combinations were compared.

RESULTS

For predicting positive urine culture, the areas under the receiver-operating characteristic curves for HD5 and HNP1-3 were 0.86 (95% confidence interval (CI): 0.81-0.92) and 0.88 (95% CI: 0.82-0.93), respectively. Compared to LE ≥ trace, the combination test "LE and HD5" increased specificity by 6% (95% CI: 3-10%) without decreasing sensitivity. In the subgroup whose urine was collected by a clean-catch method, combination tests "LE and HD5" and "HD5 and HNP1-3" increased specificity by > 10% compared to LE alone.

CONCLUSION

Urine AMP profiles are a promising novel strategy as an adjunct to urinalysis to aid UTI diagnosis in children.

Isolated Hematuria and Sterile Pyuria May Indicate Systemic Lupus Erythematosus Activity

Objective.

To identify patients presenting with isolated hematuria and/or pyuria in the absence of other systemic lupus erythematosus (SLE) disease activity, describe their demographics, and determine whether they present with evidence of SLE flare in a period adjacent to the presentation.

Methods.

We studied patients followed at the University of Toronto Lupus Clinic between 1970 and 2012. An episode of isolated hematuria (> 5 red blood cells per high power field) and/or pyuria (> 5 white blood cells per high power field) was defined as 2 consecutive visits with these findings in the absence of other concurrent SLE manifestations such as proteinuria, casts, or azotemia. We then excluded patients whose findings might be explained by urinary tract infections, menstruation, urolithiasis, and/or anticoagulation. Only patients presenting with no other SLE disease activity were included.

Results.

Isolated hematuria and/or pyuria were identified in 49 patients, of whom 17 were excluded according to the criteria above, leaving 32. Twenty-four patients had another renal manifestation 1 year before and/or after the occurrence; 27 had a non-renal manifestation 1 year before and/or after the occurrence; 3 patients had a biopsy in the same time frame, all with evidence of active lupus nephritis. Therefore the majority of patients with an occurrence of isolated hematuria and/or pyuria had evidence of renal or other non-renal SLE disease activity at a time adjacent to this presentation.

Conclusion.

Although not proven, our results suggest that these manifestations were associated with SLE activity, either before or after the episode, and therefore may represent a phase of active disease.

Changes in urine levels of substance P, vasoactive intestinal peptide and calcitonin-gene-related peptide in patients with urinary tract infections

Urinary tract infections (UTI) are important health problems and predisposing causes of UTI are not entirely known. Neuro-immune interactions play an important role in human health and disease. Capsaicin-sensitive sensory nerves which in nerve bladder extensively regulate immune system through neuropeptides such as substance P (SP), calcitonin-gene related peptide (CGRP) and vasoactive intestinal peptide (VIP). In addition these neuropeptides also have anti-bacterial effects. To determine how the levels of these peptides changes during UTI, 67 patients (50-90 years-old) diagnosed with UTI in Akdeniz University Faculty of Medicine Hospital were compared with 37 healthy people 50 years or older as the control group. Additionally, 7 patients with UTI symptoms (dysuria, urgency) but with sterile pyuria were also included in the study. Urine samples from 15 patients, whose symptoms regressed with control urine cultures being sterile, were taken after completion of the treatments. Urine neuropeptide levels were determined by ELISA. CGRP levels are significantly higher in patients with UTI, but did not associate with pyuria whereas SP and VIP levels were significantly lower in patients with sterile pyuria, indicating sensory nerve deficiency. Since CGRP exerts immunosuppressive effects, increased levels of the peptide may predispose to UTI. Furthermore, the connection between the observed sensory nerve deficiency and sterile pyuria warrants further studies.

Differentiating roseola infantum with pyuria from urinary tract infection

BACKGROUND

The aim of this study was to identify factors for differentiating roseola infantum from urinary tract infection (UTI) and to describe a cohort of infants diagnosed with roseola infantum and sterile pyuria.

METHODS

The medical records of infants diagnosed with roseola infantum or UTI were examined. Multivariate analysis was performed to identify factors associated with UTI. Demographic and clinical variables were compared between infants who had roseola infantum with or without sterile pyuria.

RESULT

There were 301 infants included: 158 in the roseola group (21, 13.3% with sterile pyuria) and 143 in the UTI group. The relative risk of UTI over roseola infantum: increased with leukocytosis (white blood cell [WBC] count >10,000/mm(3), odds ratio [OR] = 85.62) and pyuria (OR = 18.97); decreased with age (OR = 0.90); increased in boys (OR = 2.48); increased with WBC count 4000-10,000/mm(3) (OR = 4.24); and decreased with duration of fever (OR = 0.84). There was a significantly higher proportion of girls in the roseola pyuria group (81.0%) compared with the no pyuria group (44.5%, P = 0.002). A significantly higher proportion of infants in the roseola pyuria group (76.2%) received antibiotics than infants in the no pyuria group (38.0%, P = 0.002).

CONCLUSION

Leukocytosis is the strongest predictor of UTI over roseola infantum. Sterile pyuria may occur in infants with roseola infantum.

Detection of Chlamydia trachomatis and Mycoplasma hominis, genitalium and Ureaplasma urealyticum by polymerase chain reaction in patients with sterile pyuria

PURPOSE

Chlamydia trachomatis and Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma urealyticum are associated with various diseases of the urogenital tract, but they are usually not detected by routine microbiological diagnosis. To determine the occurrence of Chlamydia trachomatis, Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma urealyticum in patients with sterile pyuria.

MATERIAL/METHODS

Sterile pyuria urine samples collected during the period from February 2006 to April 2007 were tested by polymerase chain reaction (PCR) for the presence of C. trachomatis, M. hominis, M. genitalium, and U. urealyticum using specific primers for each species. A total of 200 sterile pyuria samples selected from about 2400 urine samples attending the genitourinary clinic at Al-Shifa hospital, Gaza, during the period February 2006 to April 2007 and were analyzed for routine urine examination and cultured on MacConkey agar, blood agar, and sabouraud agar to detect the presence of bacteria and Candida. The 200 samples (96 male, 104 female; aged >or=18 years) containing more than 10 leukocytes / HPF and negative for culture (showing no significant growth after 24 hr) were tested by PCR for C. trachomatis and M. hominis, M. genitalium, and U. urealyticum.

RESULTS

C. trachomatis was detected in 20 samples (10%), U. urealyticum in 10 samples (5%), M. hominis in 6 samples (3%) and M. genitalium in 2 samples (1%). The difference in occurrence of C. trachomatis was statistically insignificant between males and females (P=0.509), but it was significant (P=0.008) for U. urealyticum. M. hominis was detected only in samples collected from female patients. On the other hand, M. genitalium was detected only in men.

CONCLUSION

PCR testing of sterile pyuria showed a significant number of C. trachomatis, Mycoplasma, and Ureaplasma infections. Consequently, PCR is recommended for the detection of those microorganisms in the urine samples of sterile pyuria patients.