Contrast-enhanced voiding urosonography in the diagnosis of intrarenal reflux

Videourodynamics - role, benefits and optimal practice

Videourodynamics (VUDS) is an advanced diagnostic procedure that simultaneously combines functional and anatomical evaluation of the lower urinary tract. The goal of this synchronous assessment is to promote accurate diagnosis of the aetiology responsible for patient symptoms, improving therapeutic decision-making. Overall, high-quality VUDS is advocated when other tests such as traditional urodynamics might not provide sufficient data to guide therapy, particularly in patients with complex, persistent or recurrent dysfunctions of the lower urinary tract. Additionally, VUDS is often crucial in the follow-up monitoring of many patients with these dysfunctions. A VUDS study is frequently considered a gold standard in patients with neurogenic lower urinary tract dysfunction, female bladder outlet obstruction or congenital anomalies of the lower urinary tract. Nevertheless, this specialized test should be limited to patients in whom VUDS data add value. Particularly, reliable studies comparing the effect of diagnosis with and without imaging on management outcomes are lacking, and no standardized procedures for undertaking VUDS are available. Additionally, patients should be carefully selected for VUDS evaluation, considering the increased cost and risks associated with radiological imaging. In routine practice, clinicians should balance the additional value of synchronous imaging and the enhanced diagnostic precision of VUDS against the limitations of this approach, which mainly include an uncertain effect of VUDS on final treatment outcomes.

Reduced kidney size and renal function of high-grade vesicoureteral reflux and intrarenal reflux in contrast-enhanced voiding urosonography

BACKGROUND

Vesicoureteral reflux (VUR) is a common pediatric urological condition associated with renal scarring, hypertension, and chronic kidney disease. Contrast-enhanced voiding urosonography (ceVUS) has emerged as a promising technique for diagnosing and evaluating VUR, with intrarenal reflux (IRR) often detected using this method. This study aimed to explore the relationship between different VUR grades and IRR on ceVUS, and assess the impact of VUR and IRR on kidney size and function.

METHODS

We reviewed all ceVUS studies from January 2019 to December 2023 conducted at West China Hospital, Sichuan University. Both video clips and digital images of the ceVUS examinations were recorded. A total of 220 uretero-renal units (URUs) of 110 children (67 males and 43 females) were included in this study.

RESULTS

Among the 220 URUs assessed, 134 were diagnosed with VUR, and 25 exhibited IRR, with IRR exclusively observed in patients with grade II VUR or higher. Upon age and sex matching, the severity of IRR showed a significant positive correlation with high-grade VUR (P < 0.001). Notably, patients with high-grade VUR and IRR displayed reduced kidney size compared to those without VUR or IRR (P < 0.05). Furthermore, patients with high-grade VUR and IRR had reduced DMSA renal function (P = 0.015, P = 0.012, respectively), and patients with high-grade VUR had more DMSA scars (P = 0.027), compared with those without VUR or IRR.

CONCLUSION

Our study highlights that on ceVUS, the IRR degree was associated with the high-grade VUR, along with reductions in kidney size and renal function in patients with high-grade VUR and IRR.

The Intrarenal Reflux Diagnosed by Contrast-Enhanced Voiding Urosonography (ceVUS): A Reason for the Reclassification of Vesicoureteral Reflux and New Therapeutic Approach?

Vesicoureteral reflux (VUR) is defined as the urine backflow from the urinary bladder to the pyelo-caliceal system. In contrast, intrarenal reflux (IRR) is the backflow of urine from the renal calyces into the tubulointerstitial space. VURs, particularly those associated with IRR can result in reflux nephropathy when accompanied by urinary tract infection (UTI). The prevalence of IRR in patients with diagnosed VUR is 1-11% when using voiding cystourethrography (VCUG), while 11.9-61% when applying the contrast-enhanced voiding urosonography (ceVUS). The presence of IRR diagnosed by VCUG often correlates with parenchymal scars, when diagnosed by a 99mTc dimercaptosuccinic acid scan (DMSA scan), mostly in kidneys with high-grade VURs, and when diagnosed by ceVUS, it correlates with the wide spectrum of parenchymal changes on DMSA scan. The study performed by both ceVUS and DMSA scans showed IRRs associated with non-dilated VURs in 21% of all detected VURs. A significant difference regarding the existence of parenchymal damage was disclosed between the IRR-associated and IRR-non-associated VURs. A higher portion of parenchymal changes existed in the IRR-associated VURs, regardless of the VUR grade. That means that kidneys with IRR-associated VURs represent the high-risk group of VURs, which must be considered in the future classification of VURs. When using ceVUS, 62% of places where IRR was found were still unaffected by parenchymal changes. That was the basis for our recommendation of preventive use of long-term antibiotic prophylaxis until the IRR disappearance, regardless of the VUR grade. We propose a new classification of VURs using the ceVUS method, in which each VUR grade is subdivided based on the presence of an IRR.

Application of contrast-enhanced ultrasound in the surgical treatment of vesicoureteral reflux in children

BACKGROUND

To determine the utility of contrast-enhanced voiding urography (CeVUS) in the treatment of vesicoureteral reflux (VUR) through ureterovesical reimplantation in children.

METHODS

A total of 159 children with recurrent urinary tract infections were selected for CeVUS and voiding cystourethrography (VCUG) from December 2018 to December 2020, among whom 78 patients were eventually diagnosed with VUR. Overall, 60 pyelo-ureteric units (PUUs) were operated according to surgical indications. Accordingly, we determined the general clinical characteristics of all children, obtained two-dimensional ultrasound images, assessed the reflux status of children using the contrast-enhanced technique, and compared the obtained results via CeVUS and VCUG. Both imaging modalities were reperformed at 6, 12, and 18 months after surgery to evaluate postoperative outcomes. In particular, we assessed the consistency of the evaluation and calculated the diagnostic efficacy of CeVUS for different levels of reflux at different time points.

RESULTS

CeVUS showed considerable efficacy in the diagnosis of children with VUR. Notably, the diagnostic results of both CeVUS and VCUG achieved high agreement, with a kappa value of 0.966 (P < 0.001). The results of our follow-up at different stages and evaluation of postoperative efficacy revealed that CeVUS possessed substantial diagnostic efficacy and good consistency with VCUG.

CONCLUSION

CeVUS is an accurate and safe examination, with considerable clinical significance for diagnosing VUR in children, determining the treatment approach, conducting follow-up during treatment, and evaluating subsequent treatment outcomes.

An innovative diagnostic procedure in children: videourodynamics with contrast-enhanced voiding urosonography

Contemporary videourodynamic (VUD) investigation combines voiding cystourethrography (VCUG) and urodynamics into one study, which allows simultaneous visualization of the urinary tract by ionizing radiation alongside the measurement of sensation, capacity, compliance, and detrusor pressure during bladder filling and voiding using one double lumen catheter. Today VUD is a benchmark for evaluating the lower urinary tract disorders in children because it evaluates urinary bladder and sphincter function and visualizes bladder morphology and vesicoureteral reflux (VUR) presence at the same time. Several previous studies of fluoroscopic videourodynamics issued concerns regarding radiation exposure. This technical report aims to describe a new modality of VUD in children by replacing fluoroscopic VCUG with contrast-enhanced voiding urosonography (ceVUS). ceVUS using second-generation contrast media and harmonic imaging is a radiation-free and highly sensitive imaging modality used to detect VUR in children. We simultaneously performed an infusion of ultrasound contrast through the double lumen urodynamic catheter during urodynamic evaluation. This article describes the advantages of this method compared with a conventional technique. In addition to being radiation-free, this procedure of advanced videourodynamics method can better detect vesicoureteral reflux and intrarenal reflux combined with urodynamic disorders associated with VUR.

A narrative review on the applications of intracavitary contrast-enhanced ultrasonography in pediatric lower genitourinary anomalies

PURPOSE

We mainly aimed to perform a narrative review of clinical applications of the three intracavitary contrast-enhanced ultrasonography (CEUS) including contrast-enhanced voiding urosonography (ceVUS), contrast-enhanced retrograde urethrosonography (ceRUG), and contrast-enhanced genitosonography (ceGS) in pediatric lower genitourinary anomalies.

METHOD

A literature search in the PubMed and Web of Science databases was conducted up to 1 July 2022 on all studies published in English using the search terms "contrast-enhanced voiding urosonography", "contrast-enhanced retrograde urethrosonography", and "contrast-enhanced genitosonography". Trials were limited to pediatric subjects (ages ≤18 years) with no time restrictions. The inclusion criteria were studies on ceVUS, ceRUG, and ceGS to evaluate pediatric lower genitourinary anomalies. Two independent authors summarized the included articles.

RESULTS

Finally, a total of 48 original articles and 6 case reports or case series were included, of which 50 (93%) were only relevant to ceVUS, 3 (5%) articles involved ceGS, while only one (2%) article involved ceRUG, and 87% of the applications of ceVUS were focused on vesicoureteral reflux (VUR). We also searched 24 related reviews, of which 20 involved ceVUS in diagnosing VUR and 4 involved ceRUG and ceGS for other lower genitourinary anomalies.

CONCLUSION

Intracavitary CEUS including ceVUS, ceRUG, and ceGS in pediatrics has many advantages over other radiological examinations in diagnosing lower genitourinary anomalies. Although ceVUS is widely used in detecting VUR, ceRUG and ceGS have also become promising techniques for evaluating the urethral pathologies and urogenital sinus.

Prevalence of intrarenal reflux in pediatric patients on contrast-enhanced voiding urosonography

BACKGROUND

Intrarenal reflux may be seen with vesicoureteral reflux (VUR) when contrast from the pelvocalyceal system extends into tubules in the parenchyma. Because intrarenal reflux has been associated with scarring, detecting intrarenal reflux may influence management to avoid renal damage.

OBJECTIVE

Our objective was to evaluate the prevalence of intrarenal reflux identified on contrast-enhanced voiding urosonography (ceVUS) and its association with sex, age, grade of VUR, location in kidney and stage of bladder filling or voiding.

MATERIALS AND METHODS

CeVUS studies performed from August 2019 through July 2020 with VUR were retrospectively reviewed by two pediatric radiologists. They independently graded VUR and assessed for intrarenal reflux, noting its location and stage of bladder filling or voiding during which it occurred. The presence and location of scarring was also recorded.

RESULTS

One hundred and six ceVUS exams were reviewed with 211 kidneys evaluated (one solitary kidney). Patients were ages 2 weeks to 12 years (mean: 1.8 years) with 71 females (67%) and 35 males (33%). Grades 2 to 5 VUR were detected in 165 kidneys with intrarenal reflux seen in 42 (25.4%). Intrarenal reflux was present in 1 of 40 kidneys (2.5%) with grade 2, 10 of 67 (14.9%) with grade 3, 25 of 47 (53.2%) with grade 4 and 6 of 11 (54.5%) with grade 5 VUR. Intrarenal reflux occurred during voiding in 31 of 42 kidneys (73.8%) and was seen most often in the lower pole (71.4%) with significant association between intrarenal reflux and interpolar renal scarring (odds ration [OR] 3.92; 95% confidence interval [CI] 1.49, 10.32; P-value 0.01).

CONCLUSION

Intrarenal reflux was often seen on ceVUS, with the highest frequency occurring in young patients with grades 4 and 5 VUR and during voiding. Radiologists should have a high index of suspicion for intrarenal reflux on ceVUS, especially in young children with high-grade VUR.

The Spectrum of Parenchymal Changes in Kidneys Affected by Intrarenal Reflux, Diagnosed by Contrast-Enhanced Voiding Urosonography and DMSA Scan

PURPOSE

To describe the parenchymal defects in kidneys with intrarenal reflux (IRR) diagnosed using contrast-enhanced voiding urosonography (ceVUS) and ^99mTc-DMSA scintigraphy (DMSA scan).

MATERIALS AND METHODS

A group of 186 uretero-renal units (URUs) was analyzed using ceVUS and DMSA scans: 47 without vesicoureteral reflux (VUR) (group A) and 139 with VURs, comprising 73 VURs without (group B), and 66 with IRR (group C). VURs included non-dilating (grades I-II), mildly non-dilating (grade III), and non-dilating (grades IV-V) grades. The parenchymal changes were analyzed using a DMSA scan.

RESULTS

The median age for VUR diagnosis was 16.5 months in girls, and 8.5 months in boys (Z = 3.9; p = 0.001). IRR occurred in 51.4% of boys and in 25.9% of girls (χ² = 12.4; p < 0.001). The non-dilating VUR occurred in 44% of boys and 24.1% of girls (χ² = 7.7; p = 0.005). IRRs characterized upper and lower renal segments (81.8 and 63.6%) and middle segments (33.3%). Both incidence and increase in IRR correlated with the grade of VUR (p < 0.001). The incidence of reduced DMSA signal was statistically different among groups A + B and C, but not between groups A and B (χ² = 32.2; p < 0.001). No statistically significant relationship existed between the reduced DMSA signal and the grade of VUR in group C. The reduced DMSA signal appeared in 9.9% positions in kidneys from group A, 14% from group B, and 32% from group C. Out of all 118 IRRs, 38.1% had reduced and 61.9% had normal DMSA signal. Among 11 parenchymal scars found in all three groups, 2 belonged to group B, 9 to group C, while group A had no scars.

CONCLUSION

The parenchymal changes are the most prominent in the group with IRR, but they do not significantly differ among kidneys with different grades of VUR. VURs of higher grades are associated with a higher incidence of IRR and early clinical presentation. Scars can also appear in lower-grade VURs accompanied by IRR. Boys with VUR have earlier clinical presentation than girls, as they have significantly higher grades of VUR with a higher proportion of IRRs. Therefore, we suggest a subdivision of VURs into those with IRR and abundant parenchymal damage, and those without IRR and less parenchymal damage.

Contrast-enhanced ultrasound: a comprehensive review of safety in children

Contrast-enhanced ultrasound (CEUS) has been increasingly used in pediatric radiology practice worldwide. For nearly two decades, CEUS applications have been performed with the off-label use of gas-containing second-generation ultrasound contrast agents (UCAs). Since 2016, the United States Food and Drug Administration (FDA) has approved the UCA Lumason for three pediatric indications: the evaluation of focal liver lesions and echocardiography via intravenous administration and the assessment of vesicoureteral reflux via intravesical application (contrast-enhanced voiding urosonography, ceVUS). Prior to the FDA approval of Lumason, numerous studies with the use of second-generation UCAs had been conducted in adults and children. Comprehensive protocols for clinical safety evaluations have demonstrated the highly favorable safety profile of UCA for intravenous, intravesical and other intracavitary uses. The safety data on CEUS continue to accumulate as this imaging modality is increasingly utilized in clinical settings worldwide. As of August 2021, 57 pediatric-only original research studies encompassing a total of 4,518 children with 4,906 intravenous CEUS examinations had been published. As in adults, there were a few adverse events; the majority of these were non-serious, although very rarely serious anaphylactic reactions were reported. In the published pediatric-only intravenous CEUS studies included in our analysis, the overall incidence rate of serious adverse events was 0.22% (10/4,518) of children and 0.20% (10/4,906) of all CEUS examinations. Non-serious adverse events from the intravenous CEUS were observed in 1.20% (54/4,518) of children and 1.10% (54/4,906) of CEUS examinations. During the same time period, 31 studies with the intravesical use of UCA were conducted in 12,362 children. A few non-serious adverse events were encountered (0.31%; 38/12,362), but these were most likely attributable to the bladder catheterization rather than the UCA. Other developing clinical applications of UCA in children, including intracavitary and intralymphatic, are ongoing. To date, no serious adverse events have been reported with these applications. This article reviews the existing pediatric CEUS literature and provides an overview of safety-related information reported from UCA uses in children.