Mild hydronephrosis in newborns and infants: can ultrasound predict the presence of vesicoureteral reflux

Imaging Diagnosis of Major Kidney and Urinary Tract Disorders in Children

Background and Objectives: Diagnostic imaging is essential for evaluating urinary tract disorders, offering critical insights into renal pathology. This review examines the strengths, limitations, and clinical applications of various imaging modalities, with a focus on pediatric populations. Materials and Methods: A narrative review was conducted, synthesizing current literature on ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), nuclear medicine, and voiding cystourethrography (VCUG). Relevant studies were selected based on diagnostic accuracy, clinical utility, and safety considerations. Results: US is the preferred first-line imaging due to its safety, accessibility, and cost-effectiveness. CT excels in detecting renal calculi, trauma, and malignancies but is limited by radiation exposure. MRI offers superior soft tissue contrast without radiation but is costly and often requires sedation. Nuclear medicine evaluates renal function and scarring, while VCUG remains the gold standard for diagnosing vesicoureteral reflux and posterior urethral valves. Conclusions: Imaging modalities are vital for diagnosing and managing urinary tract disorders, with selection based on clinical needs, patient age, and safety. Ultrasound is the primary choice for its non-invasiveness and cost-effectiveness, while CT, MRI, nuclear medicine, and VCUG provide essential structural and functional insights. A balanced approach ensures accuracy while minimizing patient risk, especially in pediatrics.

ACR Appropriateness Criteria® Antenatal Hydronephrosis-Infant

Antenatal hydronephrosis is the most frequent urinary tract anomaly detected on prenatal ultrasonography. It occurs approximately twice as often in males as in females. Most antenatal hydronephrosis is transient with little long-term significance, and few children with antenatal hydronephrosis will have significant obstruction, develop symptoms or complications, and require surgery. Some children will be diagnosed with more serious conditions, such as posterior urethral valves. Early detection of obstructive uropathy is necessary to mitigate the potential morbidity from loss of renal function. Imaging is an integral part of screening, diagnosis, and monitoring of children with antenatal hydronephrosis. Optimal timing and appropriate use of imaging can reduce the incidence of late diagnoses and prevent renal scarring and other complications. In general, follow-up neonatal ultrasound is recommended for all cases of antenatal hydronephrosis, while further imaging, including voiding cystourethrography and nuclear scintigraphy, is recommended for moderate or severe cases, or when renal parenchymal or bladder wall abnormalities are suspected. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Prognostic Value of Ultrasound Grading Systems in Prenatally Diagnosed Unilateral Urinary Tract Dilatation

PURPOSE

We compared the prognostic value of anteroposterior intrasinus diameter of the renal pelvis, urinary tract dilatation and the Society for Fetal Urology grading system in children with prenatally diagnosed unilateral urinary tract dilatation.

MATERIALS AND METHODS

All newborns with prenatally diagnosed unilateral urinary tract dilatation, normal bladder and anteroposterior intrasinus diameter 10 mm or greater on the first postnatal ultrasonography were prospectively enrolled from January 2011 to February 2015. Indications for surgery were recurrent febrile urinary tract infections and/or decrease of relative renal function more than 10% on serial isotope studies and/or increasing anteroposterior intrasinus diameter greater than 20% on serial ultrasounds. Sensitivity, specificity and ROC curves were calculated to evaluate the accuracy of anteroposterior intrasinus diameter, urinary tract dilatation and Society for Fetal Urology grading system in determining which children would need surgery within 24 months.

RESULTS

A total of 57 males and 13 females were included. Of the patients 33 required surgery at a median age of 5 months (IQR 3.8 to 6.4). Urinary tract dilatation remained stable in 14 cases and decreased in 23 with a median followup of 42 months (IQR 25 to 67). Anteroposterior intrasinus diameter, urinary tract dilatation and Society for Fetal Urology scores were all correlated with the need for surgery. Anteroposterior intrasinus diameter with a threshold of 20 mm had the best prognostic value, with a sensitivity of 81.8% and a specificity of 91.7%.

CONCLUSIONS

Our study confirms that the prognostic value was comparable between anteroposterior intrasinus diameter of the renal pelvis, urinary tract dilatation and Society for Fetal Urology grading system in newborns with prenatally diagnosed unilateral urinary tract dilatation. Anteroposterior intrasinus diameter and abnormal parenchymal thickness are the most important ultrasound criteria to identify children at risk for requiring surgery.

Clinical importance of pyelocalyceal dilation diagnosed by postnatal ultrasonographic screening of the urinary tract

Background

Ultrasonographic (US) screening of the urinary tract (UT) in infants was used to determine if there is a connection between the frequency of pyelocaliceal dilation (PCD) in asymptomatic infants with normal antenatal US screening and occurrence of congenital anomalies of kidney and urinary tract (CAKUT) and urinary tract infections (UTI).

Material/Methods

US screening of the UT was performed on 1000 healthy infants, 7 days to 6 months old. Two subgroups of kidneys were described: subgroup 1 contained kidneys with anterior posterior pelvic diameter (APPD) of 5–9.9 mm, and subgroup 2 with APPD over 10 mm. US examinations and methods for detection of UTI and CAKUT were used.

Results

PCD was found in 74 infants (7.4%): 1.9% of infants had CAKUT, and 8.4% had UTI. In subgroup 1, CAKUT was found in 4 (6.3%) and UTI in 9 (14.3%) infants. In subgroup 2, CAKUT was found in 6 (54.5%), and UTI in 4 (36.4%) infants.

Conclusions

Mild PCD significantly increases the risk for CAKUT but not for UTI. Moderate to severe PCD significantly increases risk for both CAKUT and UTI. The postnatal US screening of UT is recommended for improved detection of PCD and associated CAKUT. Indirectly, postnatal US screening of UT can help in detecting people at risk for UTI in the first year of life, and therefore help prevent possible kidney damage.

Does hydronephrosis predict the presence of severe vesicoureteral reflux?

We hypothesized that, in patients with vesicoureteral reflux (VUR) grade IV or V, hydronephrosis will likely be found, if the patient has a full bladder during the renal ultrasound examination. Eight hundred thirty-seven patients were included in the study. Patients ranged in age from <1 month to 18.7 years, with a median age of 1.3 years. Five hundred sixty-nine were female and 268 were male. In this retrospective study, each patient underwent a voiding cystourethrogram (VCUG) and a renal ultrasound examination. The presence of hydronephrosis and bladder filling status in 131 renal units with VUR grade IV or V was evaluated. Sensitivity and specificity for hydronephrosis to detect the presence of VUR grades IV and V were 60 and 92 %, respectively. Positive predictive value and negative predictive value were 74 and 87 %, respectively. Odds ratios for the relationship between hydronephrosis and severe VUR was significant (p = 0.046).

CONCLUSION

In patients with grade IV or V VUR, hydronephrosis will be observed in the presence of a full bladder. Therefore, a renal ultrasound could be considered a screening test to decide on performing a VCUG.

The necessity of voiding cystourethrography in children with prenatally diagnosed hydronephrosis

The postnatal persistence of fetal hydronephrosis requires further evaluation to establish whether pathological abnormalities are present. This study determined the necessity for voiding cystourethrography (VCUG) to identify vesicoureteral reflux (VUR) in children (n = 195) with prenatally diagnosed hydronephrosis. Among the study population, the prevalence of VUR was 17.4% (24 males, 10 females). There was a poor correlation between the severity of hydronephrosis, ureteral dilatation, presence of bilateral hydronephrosis and presence of VUR. Except for the frequency of urinary tract infections and the presence of renal damage on (99m)Tc-dimercaptosuccinic acid scans, VCUG was the only reliable method for confirming VUR in this study. The diagnosis of VUR is important for the early detection of renal damage. Further information is needed to develop the optimal approach to the evaluation of prenatal hydronephrosis, with reliable parameters that avoid invasive procedures such as VCUG.

Urinary tract infection in the newborn: clinical and radio imaging studies

The objective of this study was to assess clinical characteristics and results of radio imaging studies and compare community-acquired urinary tract infection (UTI) with nosocomial UTI in 301 neonates with UTI consecutively admitted to 28 neonatal units in Spain over 3 years (community-acquired UTI, n = 250; nosocomial UTI, n = 51). UTI was diagnosed in the presence of symptoms of infection together with any colony growth for a single pathogen from urine obtained by suprapubic aspiration, or >or=10(4) CFU/ml for a single pathogen from urine obtained by urethral catheterization. Abnormal renal ultrasound was present in 37.1% of cases (34% in community-acquired UTI and 54.5% in nosocomial UTI, P < 0.01). The voiding cystourethrography (VCUG) showed vesicoureteral reflux (VUR) in 27% of cases (23.8% in community-acquired UTI and 48.6% in nosocomial UTI, P < 0.01). In patients with abnormal renal ultrasound and VUR, renal scan with dimercaptosuccinic acid (DMSA) performed early after UTI revealed cortical defects in 69.5% of cases. However, in patients with abnormal renal ultrasound and normal VCUG, DMSA also revealed cortical defects in 39% of cases. The absence of VUR in neonates with UTI and abnormal renal ultrasound does not exclude the presence of cortical defects suggestive of pyelonephritis.