Clinical Predictors for Abnormal Renal Bladder Ultrasound in Hospitalized Young Children With a First Febrile Urinary Tract Infection

Revisiting the utility of prenatal ultrasound in the routine workup of first febrile UTI: A systematic review and meta-analysis of the negative predictive value of prenatal ultrasound for identification of urinary tract abnormalities after first febrile urinary tract infection in children

CONTEXT

The current EAU/ESPU and recently retired AAP pediatric UTI guidelines recommend renal bladder ultrasound after first febrile UTI in children to screen for structural abnormalities, regardless of findings on prenatal ultrasound.

OBJECTIVE

Test the hypothesis that a normal prenatal ultrasound could rule out urinary tract abnormality on post-UTI ultrasound.

DATA SOURCES

Medline, Embase, Cochrane Library.

STUDY SELECTION

Studies including pediatric patients with first febrile UTI who had both prenatal and post-UTI ultrasound.

DATA EXTRACTION

Anatomical abnormalities detected by prenatal and post-UTI ultrasound as reported per individual study criteria were extracted. Meta-analyses of 9 studies (2981 patients) were performed using a random-effects model and composite estimates of the negative predictive value (NPV) of prenatal ultrasound were calculated.

RESULTS

Overall summary NPV of prenatal ultrasound for all pediatric patients was 77%, with heterogeneity score (I2) 97.9%. Summary NPV of prenatal ultrasound for all patients under two years of age was similar at 75%, with I2 98.2% For the 4 studies to which we could apply a more stringent definition of abnormality, summary NPV was 85% and I2 97.5% for prediction of moderate post-UTI ultrasound abnormalities and summary NPV was 93% and I2 90.4% for severe abnormalities.

DISCUSSION

While we calculated an 85% NPV for a normal prenatal ultrasound to rule out significant postnatal abnormality as defined within individual studies, substantial heterogeneity amongst publications limited the precision of our estimates. This highlights the need for more rigorous investigations with attention to timing of ultrasound and the application of clinically meaningful definitions for abnormal prenatal and post-UTI studies. This may allow judicious use of prenatal ultrasound to guide clinical management for children with first febrile UTI and minimize redundant imaging with potential for false positive results. Until then, the current guidelines are justified based on the limited and heterogenous data from the currently available published studies.

Kidney Ultrasonography After First Febrile Urinary Tract Infection in Children: A Systematic Review and Meta-analysis

Importance

Controversy exists on the clinical utility of kidney ultrasonography after first febrile urinary tract infection (UTI), and clinical practice guideline recommendations vary.

Objective

To determine the prevalence of urinary tract abnormalities detected on kidney ultrasonography after the first febrile UTI in children.

Data Sources

The MEDLINE, EMBASE, CINAHL, PsycINFO, and Cochrane Central Register of Controlled Trials databases were searched for articles published from January 1, 2000, to September 20, 2022.

Study Selection

Studies of children with first febrile UTI reporting kidney ultrasonography findings.

Data Extraction and Synthesis

Two reviewers independently screened titles, abstracts, and full texts for eligibility. Study characteristics and outcomes were extracted from each article. Data on the prevalence of kidney ultrasonography abnormalities were pooled using a random-effects model.

Main Outcomes and Measures

The primary outcome was prevalence of urinary tract abnormalities and clinically important abnormalities (those that changed clinical management) detected on kidney ultrasonography. Secondary outcomes included the urinary tract abnormalities detected, surgical intervention, health care utilization, and parent-reported outcomes.

Results

Twenty-nine studies were included, with a total of 9170 children. Of the 27 studies that reported participant sex, the median percentage of males was 60% (range, 11%-80%). The prevalence of abnormalities detected on renal ultrasonography was 22.1% (95% CI, 16.8-27.9; I2 = 98%; 29 studies, all ages) and 21.9% (95% CI, 14.7-30.1; I2 = 98%; 15 studies, age <24 months). The prevalence of clinically important abnormalities was 3.1% (95% CI, 0.3-8.1; I2 = 96%; 8 studies, all ages) and 4.5% (95% CI, 0.5-12.0; I2 = 97%; 5 studies, age <24 months). Study recruitment bias was associated with a higher prevalence of abnormalities. The most common findings detected were hydronephrosis, pelviectasis, and dilated ureter. Urinary tract obstruction was identified in 0.4% (95% CI, 0.1-0.8; I2 = 59%; 12 studies), and surgical intervention occurred in 1.4% (95% CI, 0.5-2.7; I2 = 85%; 13 studies). One study reported health care utilization. No study reported parent-reported outcomes.

Conclusions and Relevance

Results suggest that 1 in 4 to 5 children with first febrile UTI will have a urinary tract abnormality detected on kidney ultrasonography and 1 in 32 will have an abnormality that changes clinical management. Given the considerable study heterogeneity and lack of comprehensive outcome measurement, well-designed prospective longitudinal studies are needed to fully evaluate the clinical utility of kidney ultrasonography after first febrile UTI.

Imaging Practices and Implications in Young Infants With Urinary Tract Infection

OBJECTIVES

Management of infants aged ≤60 days with urinary tract infections (UTI) is challenging. We examined renal imaging in infants aged ≤60 days with UTI at a tertiary care children's hospital to identify the impact of standardizing renal ultrasound (RUS) interpretation.

METHODS

We retrospectively studied infants aged ≤60 days hospitalized for UTI or fever with urine culture and renal imaging obtained and final diagnosis of UTI. RUS initially had noncriterion-based (NCB) interpretation by experienced pediatric radiologists. For this study, a single pediatric radiologist used a criterion-based (CB) hydronephrosis grading system to reinterpret films initially classified as "abnormal" on the NCB reading. We compared final renal imaging results between NCB and CB groups.

RESULTS

Of 193 infants, 180 (93%) had inpatient RUS with 114 (63%) abnormal NCB interpretation. Of those with initially abnormal NCB interpretation, 85 OF 114 (75%) had minor and 29 OF 114 (25%) had significant abnormality by CB reinterpretation. In follow-up, the CB "minor abnormality" group showed 25% abnormal renal imaging, whereas the "significant abnormality" group showed 77% abnormal renal imaging with 54% having high-grade reflux on a voiding cystourethrogram (VCUG). Patients with CB inpatient RUS minor abnormality showed 3% abnormal RUS at follow-up, but 13% showed high-grade reflux on VCUG.

CONCLUSIONS

Standardized RUS interpretation in young infants with UTI improved the accuracy of identification of abnormalities on follow-up renal imaging. In patients with CB minor abnormality on inpatient RUS, our results suggest limited utility of follow-up RUS; however, follow-up VCUG remained useful to identify high-grade reflux.