Renal power Doppler ultrasound does not predict renal scarring after urinary tract infection

New strategy of color and power doppler sonography combined with DMSA in the assessment of acute pyelonephritis in infants

Background

The purpose of this study was to evaluate the clinical value of color and power doppler sonography (CPDS) when combined it with 99mTc-dimercaptosuccinic acid scintigraphy (DMSA) in assessment of acute pyelonephritis (APN) in infants.

Methods

A total of 79 children with APN admitted to our hospital from June 2016 to Jan 2019 were enrolled, including 52 boys and 27 girls, age range 1 month to 3 years old. All cases followed the diagnostic criteria for acute pyelonephritis and excluded anatomical abnormalities of urinary system. All 79 patients were examined by urinary ultrasonography (US), CPDS, and DMSA within 48 h of fever and analyzed the clinical value of combining the two methods in the assessment of APN in infants.

Results

Among 79 children, urinary ultrasonography revealed 2 cases of renal cortical echo changes, both located in the upper pole of the kidney, 24 cases of kidney enlargement, and 1 case of left kidney shrinkage. Ninety-five kidneys were shown to be diseased with DMSA, while 105 kidneys abnormal by CPDS. The sensitivity of CPDS was 69.4%, and the specificity was 38.1%. In children younger than 6 months, the sensitivity of CPDS was 56.9%, which was 84.2% in childeren between 6 months to 1 year, and 94.4% from 1 to 3 years old, respectively. The corresponding specificity of CPDS was 44.1, 26.7, and 35.7%. There was no significant correlation between CPDS levels and DMSA positive results. The abnormal rate of intermediate part in the kidneys was significantly lower than that in the upper and lower poles. Children with abnormal CPDS have a greater risk of renal scarring(p < 0.05).

Conclusion

Abnormalities detected by CPDS in a cohort of infants with APN poorly correlated with DMSA findings. But the sensitivity of CPDS is highly age-related, it can be used as a non-invasive helpful tool for early diagnosis of acute pyelonephritis in infants older than 6 months old.

Dimercaptosuccinic acid scintigraphy vs. ultrasound for renal parenchymal defects in children

INTRODUCTION

Dimercaptosuccinic acid (DMSA) scintigraphy is the gold standard in the evaluation of renal parenchymal defects and is widely used in the pediatric population. As more recent ultrasound equipment was purchased at our tertiary pediatric centre, our objective was to evaluate if renal ultrasound (US) results are equivalent or sufficient when compared to DMSA scintigraphy in the assessment of renal anomalies.

METHODS

The charts of all 463 patients who underwent DMSA scintigraphy between January 2009 and May 2014 at our pediatric tertiary centre were reviewed. The objective was to look for correlation between US and DMSA scan results for renal scars/dysplasia. A hundred and sixty pediatric patients followed with US and DMSA scan for a total of 285 renal units remained for evaluation after exclusions. Timing of the exams, urinary tract infection (UTI), and indication for imaging were reviewed. Results with older (105 patients) and newer (55 patients) US equipment were compared.

RESULTS

Among the 285 renal units evaluated, 39 (14%) had renal parenchymal defects shown by US and 87 (31%) by DMSA scintigraphy (sensitivity 36%, specificity 96%). The DMSA scan was normal for eight abnormal kidneys (3%) on US. The results were not statistically significant when compared to exams performed with newer or older US machines.

CONCLUSIONS

At our institution, US data are not sensitive enough to give reliable information about renal parenchymal defects, even with newer equipment. DMSA scintigraphy still remains mandatory for the evaluation of renal anomalies, but could be optional if the US exam indicates parenchymal defects.

Critical appraisal of the top-down approach for vesicoureteral reflux

Vesicoureteral reflux (VUR) has been linked to recurrent urinary tract infections (UTIs), renal scarring, hypertension, renal insufficiency and end-stage kidney disease. Different imaging strategies have been proposed to approach children presenting with UTI to sort out patients with significant VUR while minimizing patient morbidity, radiation exposure and financial burden. None of these imaging strategies is universally accepted. The“top-down approach” (TDA) aims at restricting the number of voiding cystourethrograms (VCUGs) and its associated morbidity while identifying patients with clinically-significant reflux. In this approach, children presenting with febrile UTIs are acutely investigated with dimercapto-succinic acid (DMSA) renal scans to identify patients with renal parenchymal inflammation. Those with evidence of renal affection are offered VCUG and late DMSA scan to identify VUR and permanent renal scarring, respectively. Although TDA could identify clinically-significant VUR with high sensitivity, it is not without limitations. The approach segregates patients based on the presence of DMSA cortical lesions omitting the morbidity and the economic burden of UTI. Additionally, some of DMSA lesions are attributed to congenital dysplasia and unrelated to UTI. Ionizing radiation exposure, financial costs, limited availability of DMSA scans in the acute setting, variability in interpreting the results and low yield of actionable findings on DMSA scans are some other limitations. In this review, we tried to address the drawbacks of the TDA and reinforce the value of patient-centered approach for VUR.