Intrarenal reflux, an overlooked entity - retrospective analysis of 1,166 voiding cysturethrographies in children

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.

Update and Summary of the European Association of Urology/European Society of Paediatric Urology Paediatric Guidelines on Vesicoureteral Reflux in Children

BACKGROUND AND OBJECTIVE

The prescriptive literature on vesicoureteral reflux (VUR) is still limited and thus the level of evidence is generally low. The aim of these guidelines is to provide a practical approach to the treatment of VUR that is based on risk analysis and selective indications for both diagnostic tests and interventions. We provide a 2023 update on the chapter on VUR in children from the European Association of Urology (EAU) and European Society for Paediatric Urology (ESPU) guidelines.

METHODS

A structured literature review was performed for all relevant publications published from the last update up to March 2022.

KEY FINDINGS AND LIMITATIONS

The most important updates are as follows. Bladder and bowel dysfunction (BBD) is common in toilet-trained children presenting with urinary tract infection (UTI) with or without primary VUR and increases the risk of febrile UTI and focal uptake defects on a radionuclide scan. Continuous antibiotic prophylaxis (CAP) may not be required in every VUR patient. Although the literature does not provide any reliable information on CAP duration in VUR patients, a practical approach would be to consider CAP until there is no further BBD. Recommendations for children with febrile UTI and high-grade VUR include initial medical treatment, with surgical care reserved for CAP noncompliance, breakthrough febrile UTIs despite CAP, and symptomatic VUR that persists during long-term follow-up. Comparison of laparoscopic extravesical versus transvesicoscopic ureteral reimplantation demonstrated that both are good option in terms of resolution and complication rates. Extravesical surgery is the most common approach used for robotic reimplantation, with a wide range of variations and success rates.

CONCLUSIONS AND CLINICAL IMPLICATIONS

This summary of the updated 2023 EAU/ESPU guidelines provides practical considerations for the management and diagnostic evaluation of VUR in children.

ADVANCING PRACTICE

For children with VUR, it is important to treat BBD if present. A practical approach regarding the duration of CAP is to consider administration until BBD resolution.

PATIENT SUMMARY

We provide a summary and update of guidelines on the diagnosis and management of urinary reflux (where urine flows back up through the urinary tract) in children. Treatment of bladder and bowel dysfunction is critical, as this is common in toilet-trained children presenting with urinary tract infection.

[Voiding cystourethrography : Indications, fluoroscopy technique and radiation protection]

BACKGROUND

Voiding cystourethrography continues to be the gold standard in the diagnostics of a wide range of diseases of the urinary tract in children.

MATERIAL AND METHODS

Indications, implementation of voiding cystourethrography in terms of preparation, materials used, dealing with the child and the parents as well as the standardized examination technique are presented. In particular, the technical aspects of fluoroscopy devices and criteria for good image quality are discussed. Case studies are used to illustrate the problems of frequent urological diseases.

DISCUSSION

The three standard examinations for the detection of vesicoureteral reflux (VUR), radionuclide cystography, contrast-enhanced voiding urosonography and voiding cystourethrography are compared. Their potential for detecting VUR and additional urological pathologies is discussed in detail. Furthermore, the optimized examination technique of voiding cystourethrography is presented. The applicability of the current dose reference values of the German Federal Office for Radiation Protection (BfS) in the daily routine is discussed and the feasibility of the dose reference values is explained.

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.

[Special diagnostics in pediatric urology-Ultrasound, VCUG, CT and MRI : Part 1: tips for the practice]

The diagnostics and treatment of pediatric urology patients in the clinical routine can be extremely challenging. In comparison to adult patients, congenital diseases, more time consuming examinations and limited options in addition to the parents' expectations must be taken into account in the diagnostic work up. In this first of two parts we will delve into ultrasound diagnostics as the cornerstone in the diagnostic pathway of children with hydronephrosis ans take a closer look on contrast enhanced ultrasound (CEUS). Conventional voiding cystourethrography still plays a major role in the diagnostic pathway of vesicoureteric reflux and will be treated in this article. Computed tomography should only be considered in pediatric patients in rare cases, always taking radiation into critical account. Magnetic resonance imaging provides an excellent anatomical overview without exposing the child to unnecessary radiation. This article provides an overview on the diagnostic imaging studies in pediatric urology and brings tips for the diagnostic evaluation.

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 voiding ultrasonography to detect intrarenal reflux in children: comparison with 99mTc-DMSA renal scans

Purpose

This study evaluated the diagnostic performance of contrast-enhanced voiding ultrasonography (CeVUS) for detecting intrarenal reflux (IRR) and the correlation between CeVUS-detected IRR sites and photon defect sites in acute ^99mTc-dimercaptosuccinic acid (DMSA) renal scans in pediatric patients.

Methods

Fifty-four kidneys from 27 patients (20 males and seven females; mean age, 5.6±4.1 months) who underwent CeVUS and acute DMSA renal scans for recurrent urinary tract infection (UTIs) or pyelonephritis were included. Pediatric experts compared the results of CeVUS with acute DMSA renal scans.

Results

Thirteen renal units (13/54, 24.1%) in 10 patients (nine males and one female; mean age, 6.3±3.7 months; age range, 0 to 13 months) showed vesicoureteral reflux and eight renal units (8/54, 14.8%) demonstrated IRR on CeVUS. Ten renal units in eight patients (six males and two females; mean age, 6.9±1.4 months; age range, 2 to 13 months) showed 19 photon defects on acute DMSA renal scans. Fifty-two renal units (96.3%) showed concordant results, and two renal units (3.7%) showed discordant results between CeVUS and acute DMSA renal scans. IRR accounted for 15/19 (78.9%) photon defects in eight renal units of seven patients using CeVUS. In a per-renal-unit analysis, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CeVUS were 80%, 100%, 100%, 95.7%, and 96.3%, respectively.

Conclusion

CeVUS showed good performance in detecting IRR, and the IRR sites detected by CeVUS closely correlated with photon defect sites in acute DMSA scans. CeVUS may play an important role in managing patients with recurrent UTIs or pyelonephritis with reduced radiation exposure.

Types of Parenchymal Changes Diagnosed on DMSA Scans of Kidneys Affected by Different Grades of Vesicoureteral Reflux

Background

Renal parenchymal damage and scarring usually is associated with urinary tract infection (UTI), whereas the impact of vesicoureteral reflux (VUR) on the kidneys is unclear. We aimed to compare kidneys with all grades of VUR (grades Io-V) and those without VUR by using direct radionuclide cystography, voiding cystourethrography, and findings from ^99mTc-DMSA scintigraphy (DMSA scan).

Material/Methods

The present analysis included 253 renal ureteral units (RUU) from 129 children with VUR and recurrent UTI and children with a single febrile UTI associated with abnormal ultrasonographic findings. The 6 grades of VUR (Io, I, II, III, IV, and V) and 35 RUUs without VUR were divided into 4 groups: 1. Non-dilated VUR (grades Io-II); 2. Mildly dilated VUR (grade III); 3. Dilated VUR (grades IV–V); and 4. The control group.

Results

DMSA scanning showed significant differences between the groups with non-dilated VUR, grade III VUR, grades IV–V VUR, and the control group in kidney width (χ²=30.5; P<0.001); position and shape (χ²=30.6; P<0.001); intensity of activity (χ²=38.1; P<0.001); distribution of activity (χ²=34.5; P<0.001); and existence of scars (χ²=16; P<0.001). The probability of abnormalities on DMSA scans increased with the VUR grade. However, inside the groups of dilated and non-dilated VUR we found no significant statistical differences between those characteristics.

Conclusions

Our results indicate that kidneys without VUR or with non-dilated lateral VUR and dilated VUR on the contralateral side represent 2 different categories of parenchymal changes.

Contrast-enhanced voiding urosonography in the diagnosis of intrarenal reflux

PURPOSE

Although contrast-enhanced urosonography (ceVUS) has shown capable diagnostic accuracy for the diagnosis of vesicoureteral reflux (VUR) in children, the ability of ceVUS to detect intrarenal reflux (IRR) is considered limited. The purpose of our study is to assess the ability of ceVUS to detect IRR as well as its association with age, gender, and the grade of VUR.

METHODS

This study included 5153 children who were referred to our clinic for ceVUS. All children underwent sonographic examinations, which were performed on a LOGIQ S8 machine equipped with dedicated software for contrast-enhanced studies with harmonic imaging. Standard ultrasound of the urinary tract was followed by bladder catheterisation and instillation of physiological normal saline and the US contrast medium (SonoVue^®, Bracco).

RESULTS

VUR was diagnosed by ceVUS in 1959 out of 5153 children (38%), of whom IRR was found in 233 of 1959 children (11.9%). A total of 285 ureteral units showing IRR were found. High grades of VUR (IV + V) with IRR were found in a total of 235 of 285 (82.81%) renal units. Bilateral IRR was found in 53 patients, usually with a high-grade VUR on both sides. Most children had VUR grade IV, predominantly those < 12 months. The younger the child, the higher the likelihood of higher-grade VUR (p = 0.02).

CONCLUSION

ceVUS, combined with harmonic imaging and second-generation ultrasound contrast media, enabled IRR detection in almost 12% of our patients with VUR. IRR is most commonly found in children under 1 year of age with VUR grades IV and V.

Contrast-enhanced voiding urosonography for the diagnosis of vesicoureteral reflux and intrarenal reflux: a comparison of diagnostic performance with fluoroscopic voiding cystourethrography

Purpose

This study evaluated the diagnostic performance of contrast-enhanced voiding urosonography (ce-VUS) using a second-generation ultrasound contrast agent for the diagnosis of vesicoureteral reflux (VUR) and intrarenal reflux (IRR), and compared it with that of standard fluoroscopic voiding cystourethrography (VCUG).

Methods

Thirty-two consecutive children from April to October 2019 were included in this study. ce-VUS and VCUG were performed simultaneously by two operators with intravesical infusion of a mixture of ultrasound contrast medium, iodinated contrast medium and water. Two pediatric radiologists independently reviewed the ce-VUS and VCUG images and reported the presence and degree of VUR (grades I-V), and the presence and type of IRR.

Results

Twenty-seven of 63 urinary systems showed VUR. Interobserver agreement for VUR grading was very good for both examinations (κ=0.87; 95% confidence interval [CI], 0.82 to 0.92 for ce-VUS and κ=0.92; 95% CI, 0.87 to 0.96 for VCUG). The detection rate of VUR showed no significant difference between the two examinations (P=0.370). Four cases of VUR were missed on ce-VUS, while one case of VUR was missed on VCUG. All four false-negative cases on ce-VUS were grade 1 VUR. The two examinations showed very good agreement regarding VUR grading (κ =0.89; 95% CI, 0.81 to 0.96). IRR was more frequently detected with ce-VUS than with VCUG (10 cases with ce-VUS vs. 3 cases with VCUG, P=0.016).

Conclusion

ce-VUS showed very good agreement with VCUG for detecting grade 2 VUR and above, while grade 1 VUR was sometimes missed with ce-VUS. IRR was more frequently detected with ce-VUS than with VCUG.

Intrarenal Reflux in the Light of Contrast-Enhanced Voiding Urosonography

Purpose: The aim of this study was to analyze the incidence of intrarenal reflux (IRR) among vesicoureteral refluxes (VURs), diagnosed by contrast-enhanced voiding urosonography (ceVUS), to define VURs which are positive to IRR and their locations in the kidney. Materials and Methods: Seventy patients with VURs, including 103 uretero-renal units (URUs) with VURs of grades II-V (37 URUs were excluded because of renal anomalies or absence of VUR) were examined with ceVUS due to recurrent febrile UTI or first febrile UTI accompanied by abnormalities on renal ultrasonography. Patients were examined on GE Logiq S8 ultrasound machine, using second generation of ultrasound contrast agent. Results: Out of 103 VURs, 51 (49.51%) had IRR regardless the grade of VUR, showing increase in IRR incidence with VUR severity (p < 0.0001). The median age at the time of IRR diagnosis was 5 months (IQR, 3-14.3), whereas in patients without IRR, it was 15.5 months (IQR, 5-41.5), (p = 0.0069). IRR was most common in superior pole (80%), followed by inferior pole (62.7%), and middle segments (37%), and to all segments (27%) (p < 0.0001). Conclusion: In the present study, patients with IRR-associated VUR showed earlier clinical presentation. The distribution of IRRs corresponded to the natural distribution of composed papillae types II and III, while the incidence of IRR increased with severity of VUR. Further clinical studies may point to the importance of considering IRR in the future classification of VUR.