Ultrasonography as predictor of permanent renal damage in infants with urinary tract infection

Accuracy of Ultrasound in Identifying Renal Scarring as Compared to DMSA Scan

OBJECTIVE

To assess the accuracy of renal ultrasound (RUS) in detecting renal scarring (RS).

METHODS

All initial DMSA scans performed from 2006 to 2009 for history of urinary tract infection (UTI) or vesicoureteral reflux (VUR) in patients under 14 years old were identified, and clinical history obtained via chart review. Patients who had RUS within 4 months of DMSA scan and no documented UTI during that interval were included. Decreased uptake of tracer associated with loss of contours or cortical thinning defined a positive DMSA study. Increased echogenicity/dysplasia, cortical thinning, atrophic kidney and/or abnormal corticomedullary differentiation defined a positive RUS. The sensitivity and specificity of RUS in identifying RS were calculated using DMSA scan as the gold standard.

RESULTS

A total of 144 patients had initial DMSA scans performed for UTI or VUR, with a RUS within 4 months, and no UTI between the 2 studies. Ninety-five of 144 (66%) had RS on DMSA and 49/144 (34%) did not. Patients with or without RS on DMSA were not different in gender (P = .073), age (P = .432), insurance (P = 1.000) or VUR grade (P = .132). Only 39/144 (27.1%) patients had positive RUS. The sensitivity of RUS for RS was 35.8% and the specificity was 89.8%, leading to an accuracy of 54.2% (95%CI; 45.7-62.5%, P = .999).

CONCLUSION

RUS demonstrated poor sensitivity for RS visualized on DMSA scan. This suggests that RUS is a poor screening test for RS or indicators of future renal scar. A normal ultrasound does not rule out RS or risk of future renal scar. Specificity of RUS was excellent.

Top-down approach is possible strategy for predicting breakthrough fUTIs and renal scars in infants

BACKGROUND

Acute-phase technetium-99 m dimercaptosuccinic acid (DMSA) scintigraphy is recommended for initial imaging in children with febrile urinary tract infection (fUTI). Recently, the importance of identifying patients at risk of recurrent fUTI (r-fUTI) has been emphasized. To clarify the effectiveness of DMSA scintigraphy for predicting r-fUTI in infants, we investigated the relationship between defects on DMSA scintigraphy and r-fUTI.

METHODS

Seventy-nine consecutive infants (male: female, 60:19) with fUTI were enrolled in this study. DMSA scintigraphy was performed in the acute phase, and patients with defect underwent voiding cystourethrography and chronic-phase (6 months later) DMSA scintigraphy. Patients were followed on continuous antibiotic prophylaxis (CAP).

RESULTS

Defects on acute-phase DMSA scintigraphy were observed in 32 children (40.5%) of 79. The mean follow-up observation period was 17.0 ± 10.1 months. Four patients had r-fUTI (5%). Two of them had defects on DMSA scintigraphy in both the acute phase and chronic phase, and had bilateral vesicoureteral reflux (VUR) grade IV. Two others had r-fUTI without defects on DMSA and did not have VUR. Twelve patients had defect on chronic-phase DMSA scintigraphy and four of them had no VUR.

CONCLUSIONS

The top-down approach is a possible method for predicting r-fUTI in infants and does not miss clinically significant VUR. Also, given that the prevalence of r-fUTI was 5% regardless of the presence of defects on acute-phase DMSA, then, in conjunction with genital hygiene and CAP, acute-phase DMSA might be unnecessary if chronic-phase DMSA is performed for all patients to detect renal scar.

Dimercaptosuccinic acid scan or ultrasound in screening for vesicoureteral reflux among children with urinary tract infections

BACKGROUND

There is considerable interest in detecting vesicoureteral reflux (VUR) because its presence, especially when severe, has been linked to an increased risk of urinary tract infections and renal scarring. Voiding cystourethrography (VCUG), also known as micturating cystourethrography, is the gold standard for the diagnosis of VUR, and the grading of its severity. Because VCUG requires bladder catheterisation and exposes children to radiation, there has been a growing interest in other screening strategies that could identify at-risk children without the risks and discomfort associated with VCUG.

OBJECTIVES

The objective of this review is to evaluate the accuracy of two alternative imaging tests - the dimercaptosuccinic acid renal scan (DMSA) and renal-bladder ultrasound (RBUS) - in diagnosing VUR and high-grade VUR (Grade III-V VUR).

SEARCH METHODS

We searched MEDLINE, EMBASE, BIOSIS, and the Cochrane Register of Diagnostic Test Accuracy Studies from 1985 to 31 March 2016. The reference lists of relevant review articles were searched to identify additional studies not found through the electronic search.

SELECTION CRITERIA

We considered published cross-sectional or cohort studies that compared the results of the index tests (DMSA scan or RBUS) with the results of radiographic VCUG in children less than 19 years of age with a culture-confirmed urinary tract infection.

DATA COLLECTION AND ANALYSIS

Two authors independently applied the selection criteria to all citations and independently abstracted data. We used the bivariate model to calculate summary sensitivity and specificity values.

MAIN RESULTS

A total of 42 studies met our inclusion criteria. Twenty studies reported data on the test performance of RBUS in detecting VUR; the summary sensitivity and specificity estimates were 0.44 (95% CI 0.34 to 0.54) and 0.78 (95% CI 0.68 to 0.86), respectively. A total of 11 studies reported data on the test performance of RBUS in detecting high-grade VUR; the summary sensitivity and specificity estimates were 0.59 (95% CI 0.45 to 0.72) and 0.79 (95% CI 0.65 to 0.87), respectively. A total of 19 studies reported data on the test performance of DMSA in detecting VUR; the summary sensitivity and specificity estimates were 0.75 (95% CI 0.67 to 0.81) and 0.48 (95% CI 0.38 to 0.57), respectively. A total of 10 studies reported data on the accuracy of DMSA in detecting high-grade VUR. The summary sensitivity and specificity estimates were 0.93 (95% CI 0.77 to 0.98) and 0.44 (95% CI 0.33 to 0.56), respectively.

AUTHORS' CONCLUSIONS

Neither the renal ultrasound nor the DMSA scan is accurate enough to detect VUR (of all grades). Although a child with a negative DMSA test has an < 1% probability of having high-grade VUR, performing a screening DMSA will result in a large number of children falsely labelled as being at risk for high-grade VUR. Accordingly, the usefulness of the DMSA as a screening test for high-grade VUR should be questioned.

Accuracy of ultrasonography in predicting vesicoureteral reflux in children: A meta-analysis

OBJECTIVE

The aim of this study was to assess the existing evidence on the accuracy of renal and bladder ultrasonography in predicting vesicoureteral reflux in children with first urinary tract infection.

MATERIALS AND METHODS

The CENTRAL, MEDLINE, Embase and Web of Science data sources were searched. A random effects meta-analysis was conducted.

RESULTS

Fourteen studies, involving 3544 participants, fulfilled the inclusion criteria. The risk of bias and concern regarding applicability were considered high in four studies. The pooled sensitivity was 0.37 [95% confidence interval (CI) 0.34 to 0.40], specificity 0.81 (95% CI 0.80 to 0.83), positive likelihood ratio 2.0 (95% CI 1.61 to 2.50), negative likelihood ratio 0.75 (95% CI 0.65 to 0.86), diagnostic odds ratio 3.03 (95% CI 2.10 to 4.37) and area under the curve 0.72.

CONCLUSION

There is no evidence that renal and bladder ultrasonography should be recommended as a test to predict a vesicoureteral reflux in children with their first urinary tract infection.

Role of Renal Ultrasonography in Predicting Vesicoureteral Reflux and Renal Scarring in Children Hospitalized with a First Febrile Urinary Tract Infection

BACKGROUND

This study was designed to examine the capability of renal ultrasonography (US) for predicting vesicoureteral reflux (VUR) and renal scarring (RS), and to assess, using initial US, the significant urologic abnormalities that impact on management of children hospitalized with a first febrile urinary tract infection (UTI).

METHODS

Hospitalized children aged ≤ 2 years with a first febrile UTI were prospectively evaluated using imaging studies, including (99m)Tc dimercaptosuccinic acid (DMSA) scan, US, and voiding cystourethrography.

RESULTS

Of the 310 children analyzed (195 boys and 115 girls), 105 (33.9%) had abnormal US. Acute DMSA scans were abnormal in 194 children (62.6%), including 89 (45.9%) with concomitant abnormal US. There was VUR in 107 children (34.5%), including 79 (25.5%) with Grades III-V VUR. The sensitivity and negative predictive values of US were 52.3% and 75.1%, respectively, for Grades I-V VUR and 68.4% and 87.8%, respectively, for Grades III-V VUR. Eighty-five children (27.4%) had RS, including 55 (64.7%) with abnormal US. Of the 105 children with abnormal US, 33 (31.4%) needed subsequent management (surgical intervention, parental counseling, or follow up of renal function). Nephromegaly on initial US and Grades III-V VUR were risk factors of RS.

CONCLUSION

Abnormal US may carry a higher probability of Grades III-V VUR and RS, and can affect subsequent management in a significant number of children. Nephromegaly on initial US and Grades III-V VUR are strongly associated with an increased risk for RS. Thus, US should be performed on children after a first febrile UTI and children with normal US may not require voiding cystourethrography.

Update on the approach of urinary tract infection in childhood

OBJECTIVE

Urinary tract infection (UTI) is the most common bacterial infection in childhood. UTI may be the sentinel event for underlying renal abnormality. There are still many controversies regarding proper management of UTI. In this review article, the authors discuss recent recommendations for the diagnosis, treatment, prophylaxis, and imaging of UTI in childhood based on evidence, and when this is lacking, based on expert consensus.

SOURCES

Data were obtained after a review of the literature and a search of Pubmed, Embase, Scopus, and Scielo.

SUMMARY OF THE FINDINGS

In the first year of life, UTIs are more common in boys (3.7%) than in girls (2%). Signs and symptoms of UTI are very nonspecific, especially in neonates and during childhood; in many cases, fever is the only symptom.

CONCLUSIONS

Clinical history and physical examination may suggest UTI, but confirmation should be made by urine culture, which must be performed before any antimicrobial agent is given. During childhood, the proper collection of urine is essential to avoid false-positive results. Prompt diagnosis and initiation of treatment is important to prevent long-term renal scarring. Febrile infants with UTIs should undergo renal and bladder ultrasonography. Intravenous antibacterial agents are recommended for neonates and young infants. The authors also advise exclusion of obstructive uropathies as soon as possible and later vesicoureteral reflux, if indicated. Prophylaxis should be considered for cases of high susceptibility to UTI and high risk of renal damage.

Renal damage detected by DMSA, despite normal renal ultrasound, in children with febrile UTI

OBJECTIVES

2011 American Academy of Pediatrics guidelines recommended renal-bladder ultrasound (RBUS) as the only evaluation after febrile urinary tract infection (FUTI) in infants aged 2-24 months. We determined the sensitivity, specificity, and false negative rate of RBUS to identify DMSA-detected renal damage in this age group as well as in older children.

METHODS

Consecutive patients referred to pediatric urology with a history of FUTI underwent DMSA ≥ 3 months after FUTI. Abnormal RBUS was defined as: Society of Fetal Urology hydronephrosis grades I-IV; hydroureter ≥ 7 mm; renal scar defined as focal parenchymal thinning; and/or size discrepancy ≥ 1 cm between kidneys. Abnormal DMSA was presence of any focal uptake defects and/or split renal function < 44%. We calculated sensitivity, specificity, positive and negative predictive values, and false negative rates of RBUS compared to DMSA.

RESULTS

618 patients (79% female), median age 3.4 years, were referred for FUTIs. Of the 512 (83%) with normal RBUS, 99 (19%) had abnormal DMSA. Children with normal RBUS after their first FUTI had abnormal DMSA in 15/151 (10%) aged ≤ 24 months and 23/119 (19%) aged > 24 months. RBUS had poor sensitivity (34%) and low positive predictive value (47%) to identify patients with renal damage. 99/149 (66%) children with renal damage on DMSA had normal RBUS.

CONCLUSION

After FUTI, 66% of children with reduced renal function and/or renal cortical defects found by DMSA scintigraphy had a normal RBUS. Since abnormal DMSA may correlate with increased risk for VUR, recurrent FUTI and renal damage, our data suggest RBUS alone will fail to detect a significant proportion of patients at risk. The data suggest that imaging after FUTI should include acute RBUS and delayed DMSA, reserving VCUG for patients with abnormal DMSA and/or recurrent FUTI.

Predictive risk factors in childhood urinary tract infection, vesicoureteral reflux, and renal scarring management

Approaches to the management of children with urinary tract infection (UTI), vesicoureteral reflux (VUR), and renal scars have been challenged and have become controversial over the past decade. It is difficult to determine when, how, and which patients will benefit from the diagnosis and management of this condition. Therefore, the issues of diagnostic imaging, observation, follow-up, and intervention tend to be decided more on a case-by-case basis, rather than by using an algorithm. Over the past few years, there have been advances in the identification of risk factors that predispose patients with UTI to present with VUR, to develop recurrent UTIs and renal scars, to have deteriorating renal function, to show VUR improvement and/or spontaneous resolution, and to be candidates for and benefit from early surgical intervention.

Evaluation of children with urinary tract infection--impact of the 2011 AAP guidelines on the diagnosis of vesicoureteral reflux using a historical series

OBJECTIVE

To clarify the impact of the updated American Academy of Pediatrics guidelines for the evaluation of children presenting with initial febrile urinary tract infection (UTI) on the diagnosis of vesicoureteral reflux (VUR) in children with normal renal sonograms.

MATERIALS AND METHODS

Children with VUR followed between 2002 and 2004 were evaluated using criteria specified in the AAP guidelines. A total of 49 children (42 girls) who were 2-24 months of age at diagnosis of VUR made following initial febrile UTI were included.

RESULTS

40.8% of ultrasounds were abnormal. While children with abnormal ultrasounds were more likely to have scintigraphic evidence of renal damage than children with normal ultrasounds (50% vs 17%, p = 0.026), one third of the children with abnormal renal scans had normal RBUS. There was no statistically significant difference in diagnosis of grade 3 or higher VUR between groups (p = 0.136).

CONCLUSIONS

Most children in this series would not have been diagnosed with VUR after initial febrile UTI. More worrisome, 17.2% of children with normal ultrasound had renal injury identified on renal scanning, and 62.1% had grade 3 or higher VUR. These findings reinforce concerns that the new guidelines may miss or delay diagnosis of clinically significant VUR.

Urinary proteome analysis to exclude severe vesicoureteral reflux

OBJECTIVES

High-grade vesicoureteral reflux (VUR, grade IV or V) is a risk factor for renal scarring, impaired renal function, and arterial hypertension. Voiding cystourethrography is the gold standard for detecting the severity of VUR. High-grade VUR is present in the minority of children with urinary tract infection (UTI), thus exposing the majority to invasive diagnostics that have no surgical consequence. We therefore aimed at establishing a noninvasive test to identify children with high-grade VUR.

METHODS

In a case-control study, a specific urinary proteome pattern was established by capillary electrophoresis coupled to mass spectrometry in 18 patients with primary VUR grade IV or V, distinguishing these from 19 patients without VUR after UTI. This proteome pattern was independently validated in a blinded cohort of 17 patients with VUR grade IV or V and 19 patients without VUR.

RESULTS

Sensitivity in detecting VUR grade IV or V in the blinded study was 88%, specificity was 79%. The test's accuracy was independent of age, gender, and grade of VUR in the contralateral kidney. The odds ratio of suffering from VUR grade IV or V when tested positive was 28 (95% confidence interval: 4.5 to 176.0).

CONCLUSIONS

This noninvasive test is ready for prospective validation in large cohorts with the aim of identifying those children with UTI and hydronephrosis in need of further invasive diagnostics, such as voiding cystourethrography, thus sparing most children without pathologic urinary proteome patterns from additional diagnostics.

Adequacy of paediatric renal tract ultrasound requests and reports in a general radiology department

BACKGROUND

According to current guidelines, US is the most important modality for imaging urinary tract infections (UTI) in children.

OBJECTIVES

(1) To assess the adequacy of paediatric renal US requests and reports in a general radiology department, and correlate the request adequacy and the performing radiologist's experience with report adequacy. (2) To determine the yield of abnormal findings.

MATERIALS AND METHODS

Retrospective review of renal US requests. The information was scored: requests 0-3 (3 as highest adequacy) and reports 0-21 (21 as highest adequacy). Correlation tests used included Spearman's correlation, Kruskal-Wallis test, Chi-square test of independence and Fisher exact test.

RESULTS

Mean report adequacy score was 6.67/21. Trainees did 87% of all scans and performed better (score 6.76) than the staff radiologists (score 6.08). Hydronephrosis was the most common abnormality. There was no correlation between request or reporter rank and reporting adequacy.

CONCLUSION

Renal US requests and reports are inadequate. To improve reporting standards for trainees and specialists, a renal ultrasound reporting template was designed for use.

Economic and radiation costs of initial imaging approaches after a child's first febrile urinary tract infection

BACKGROUND. The traditional initial imaging approach following pediatric urinary tract infection is the "bottom-up" approach (cystogram and renal ultrasound). Recently, the "top-down" approach (nuclear renal scan followed by cystogram for abnormal scans only) has gained increasing attention. The relative cost and radiation doses of these are unknown METHODS. The authors used a decision model to evaluate these imaging approaches. Cost and effective radiation dose estimates, including sensitivity analyses, were based on one-time imaging only. RESULTS. Comparing hypothetical cohorts of 100 000 children, the top-down imaging approach cost $82.9 million versus $59.2 million for the bottom-up approach. Per-capita effective radiation dose was 0.72 mSv for top-down compared with 0.06 mSv for bottom-up. CONCLUSIONS. Routine use of nuclear renal scans in children following initial urinary tract infection diagnosis would result in increased imaging costs and radiation doses as compared to initial cystogram and ultrasound. Further data are required to clarify the long-term clinical implications of this increase.

Imaging strategy for infants with urinary tract infection: a new algorithm

PURPOSE

We analyzed clinical data for prediction of permanent renal damage in infants with first time urinary tract infection.

MATERIALS AND METHODS

This population based, prospective, 3-year study included 161 male and 129 female consecutive infants with first time urinary tract infection. Ultrasonography and dimercapto-succinic acid scintigraphy were performed as acute investigations and voiding cystourethrography within 2 months. Late scintigraphy was performed after 1 year in infants with abnormality on the first dimercapto-succinic acid scan or recurrent febrile urinary tract infections. End point was renal damage on the late scan.

RESULTS

A total of 270 patients had end point data available, of whom 70 had renal damage and 200 did not. Final kidney status was associated with C-reactive protein, serum creatinine, temperature, leukocyturia, non-Escherichia coli bacteria, anteroposterior diameter on ultrasound and recurrent febrile urinary tract infections. In stepwise multiple regression analysis C-reactive protein, creatinine, leukocyturia, anteroposterior diameter and non-E.coli bacteria were independent predictors of permanent renal damage. C-reactive protein 70 mg/l or greater combined with anteroposterior diameter 10 mm or greater had sensitivity of 87% and specificity of 59% for renal damage. An algorithm for imaging of infants with first time urinary tract infection based on these results would have eliminated 126 acute dimercapto-succinic acid scans compared to our study protocol, while missing 9 patients with permanent renal damage.

CONCLUSIONS

C-reactive protein can be used as a predictor of permanent renal damage in infants with urinary tract infection and together with anteroposterior diameter serves as a basis for an imaging algorithm.