Pediatric uroradiology: state of the art

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.

Dietl crisis: Presentation and imaging findings in a 7-year-old boy

Intermittent ureteropelvic junction obstruction, or Dietl crisis, is a rare entity with sparse reports in published literature. Establishing the diagnosis is challenging given its intermittent nature. We report a case of Dietl crisis, focusing on ultrasound (US) and magnetic resonance urography (MRU) findings in a 7-year-old boy with recurrent episodes of colicky abdominal pain prompting multiple visits to the emergency department. Severe left hydronephrosis was visualized on US during one episode with complete resolution on follow-up US. MRU demonstrated severe left hydronephrosis with delayed calyceal transit time, time-to-peak enhancement, and excretion. There was no aberrant blood vessel. Surgical pyeloplasty provided complete symptomatic resolution. MRU can be a valuable tool in eliciting and dynamically confirming the diagnosis of Dietl crisis.

Feasibility and Quality Determinants of 3D Sonography in Children With Hydronephrosis

The objective was to determine the image quality of 3D diagnostic medical sonography (DMS) in children with hydronephrosis. 3D DMS was assessed based on 24 pediatric patients. Image quality was evaluated by two radiologists and a sonographer in terms of rib shadowing, cut-off parenchymal edges, motion artifact, and overall quality. The interreader reliability and relation between image quality and other variables were calculated. The results were based on images of 32 hydronephrotic kidneys. The average quality scoring of the images was quite high. Rib shadowing, cut-off edges, and motion artifact were present in the majority of the cases. The interreader reliability for overall quality, rib shadowing, cut-off, and motion was quite high. There was a correlation between the Society for Fetal and Neonatal Urology’s hydronephrosis grade and higher cut-off edges. Larger kidneys were more likely to show cut-off, motion, and lower quality scores. In this cohort of infants and toddlers with hydronephrotic kidneys, 3D DMS demonstrated good image quality; however, artifacts were attributed to kidney size and severity of hydronephrosis.

Pre-procedural scout radiographs are unnecessary for routine pediatric fluoroscopic examinations

BACKGROUND

Although practice patterns vary, scout radiographs are often routinely performed with pediatric fluoroscopic studies. However few studies have evaluated their utility in routine pediatric fluoroscopy.

OBJECTIVE

To evaluate the value of scout abdomen radiographs in routine barium or water-soluble enema, upper gastrointestinal (GI) series, and voiding cystourethrogram pediatric fluoroscopic procedures.

MATERIALS AND METHODS

We retrospectively evaluated 723 barium or water-soluble enema, upper GI series, and voiding cystourethrogram fluoroscopic procedures performed at our institution. We assessed patient history and demographics, clinical indication for the examination, prior imaging findings and impressions, scout radiograph findings, additional findings provided by the scout radiograph that were previously unknown, and whether the scout radiograph contributed any findings that significantly changed management.

RESULTS

We retrospectively evaluated 723 fluoroscopic studies (368 males and 355 females) in pediatric patients. Of these, 700 (96.8%) had a preliminary scout radiograph. Twenty-three (3.2%) had a same-day radiograph substituted as a scout radiograph. Preliminary scout abdomen radiographs/same-day radiographs showed no new significant findings in 719 (99.4%) studies. New but clinically insignificant findings were seen in 4 (0.6%) studies and included umbilical hernia, inguinal hernia and hip dysplasia. No findings were found on the scout radiographs that would either alter the examination performed or change management with regard to the exam.

CONCLUSION

Pre-procedural scout abdomen radiographs are unnecessary in routine barium and water-soluble enema, upper GI series, and voiding cystourethrogram pediatric fluoroscopic procedures and can be substituted with a spot fluoroscopic last-image hold.

Off-label-use of sulfur-hexafluoride in voiding urosonography for diagnosis of vesicoureteral reflux in children: A survey on adverse events

AIM

To evaluate the risk profile of sulfur hexafluoride in voiding urosonography (VUS) based on a large cohort of children.

METHODS

Since 2011 sulfur hexafluoride (SH, SonoVue^®, Bracco, Italy) is the only ultrasound contrast available in the European Union and its use in children has not been approved. Within a 4-year-period, 531 children with suspected or proven vesicoureteral reflux (f/m = 478/53; mean age 4.9 years; 1 mo-25.2 years) following parental informed consent underwent VUS with administration of 2.6 ± 1.2 mL SH in a two-center study. A standardized telephone survey on adverse events was conducted three days later.

RESULTS

No acute adverse reactions were observed. The survey revealed subacute, mostly self-limited adverse events in 4.1% (22/531). The majority of observed adverse events (17/22) was not suspected to be caused by an allergic reaction: Five were related to catheter placement, three to reactivated urinary tract infections, five were associated with perineal disinfection before voiding urosonography or perineal dermatitis and four with a common cold. In five patients (0.9%) hints to a potential allergic cause were noted: Perineal urticaria was reported in three interviews and isolated, mild fever in two. These were minor self-limited adverse events with a subacute onset and no hospital admittance was necessary. Ninety-six point two percent of the parents would prefer future VUS examinations with use of SH.

CONCLUSION

No severe adverse events were observed and indications of self-limited minor allergic reactions related to intravesical administration of SH were reported in less than 1%.

Radiation exposure contribution of the scout abdomen radiograph in common pediatric fluoroscopic procedures

BACKGROUND

Contrast enema, voiding cystourethrography and upper gastrointestinal studies are the most common fluoroscopic procedures in children. Scout abdomen radiographs have been routinely obtained prior to fluoroscopy and add to the radiation exposure from these procedures. Elimination of unnecessary routine scout radiographs in select studies might significantly reduce radiation exposure to children and improve the overall benefit-to-risk ratio of these fluoroscopic procedures.

OBJECTIVE

To determine the radiation exposure contribution of the preliminary/scout abdomen radiographs with respect to the radiation exposure of the total procedure.

MATERIALS AND METHODS

We retrospectively collected demographic information and radiation exposure values of dose area product (in Gy-cm(2)) and entrance air kerma (in mGy) - initially for the scout abdomen radiographs done prior to fluoroscopy and subsequently the total procedural radiation values (the combined values of the scout radiograph and fluoroscopic radiation exposure) - in children who underwent contrast enemas, voiding cystourethrograms and upper gastrointestinal studies in a 4-month period. The radiation parameters, including fluoroscopy time, dose area product and entrance air kerma, were available in the log book maintained in the fluoroscopy suite. Fluoroscopy procedures were performed on a single fluoroscopy machine using four frames per second pulse rate and other radiation-minimizing techniques. Usage of the grid to obtain scout radiographs was also recorded. The proportion of radiation exposure from the scout radiograph relative to that of the total procedure was calculated by dividing the individual parameters of the scout to the total procedural values and multiplied by 100 to express these values as a percentage. We calculated mean, median and range and performed statistical analysis of the data.

RESULTS

A total of 151 procedures performed on 71 males and 80 females qualified for the study. The age range of the patients was 2 days to 18 years, with a mean of nearly 3.5 years (40 months) and median of 15 months. There were 63 upper gastrointestinal studies, 65 voiding cystourethrography studies and 23 contrast enema studies. The fluoroscopy time for all procedures combined ranged from 0.1 min (6 s) to 2 min, with mean and median values of 0.4 min and 0.3 min, respectively. The fractional radiation exposure contribution for the dose area product of scout abdomen radiograph to the total procedure ranged from 4% to 98%, with mean and median values of 51% and 49%, respectively. The fractional contribution of the scout radiograph to the total procedure for the entrance air kerma values ranged from 6% to 97%, with mean and median values of 29% and 26%, respectively. There was a significant negative correlation (P<0.001) between fluoroscopy radiation time and the proportion of radiation parameters of scout radiograph to total procedural values.

CONCLUSION

Scout radiographs can contribute a significant proportion (median values of approximately 50% for the dose area product and 26% for the entrance air kerma) of radiation exposure in common fluoroscopy procedures in children.

A case-based approach to UTI imaging – making sense of the guidelines

Urinary tract infections (UTIs) are common amongst children and invariably result in imaging tests to look for correctable causes that may predispose the child to infection. The objective of imaging is to identify those children at risk of long-term renal damage. The ideal imaging algorithm is extensively debated in the literature owing to the lack of evidence-based data, evolving theories on the pathophysiology of UTI and vesicoureteric reflux (VUR). The present article provides a case-based approach to the imaging of UTIs and proposes guidelines relevant to the South African setting.

Significance of Sonographically Demonstrated Ureteral Dilatation in Evaluation of Vesicoureteral Reflux Verified with Voiding Urosonography in Children with Urinary Tract Infection

Objectives:

The aim of this study was to determine sensitivity, specificity, and predictive values of sonographically demonstrated ureteral dilatation in detecting vesicoureteral reflux (VUR).

Methods:

Ethical approval from the Ethical Committee of Clinical Center University of Sarajevo and parental consent were obtained for this prospective study involving 120 children with history of urinary tract infections (UTIs). Ultrasound examination included the evaluation of the urinary tract, with a special emphasis on evaluation of ureteral dilatation. Voiding urosonography (VUS) was carried out according to a standard protocol with the use of ultrasound contrast agent Sono Vue of second generation. Ureteral diameter greater than 3 mm was considered pathological. Proven VUR was graded into one of three stages.

Results:

Infectio tracti urinarii recidivans was referral diagnosis in the majority of patients. The average age of patients was 4.33 ± 3.88 years (from 2 months to 16 years of age). VUS findings were normal in 59 (49.2%), and pathological in 61 (50.8%) patients. Statistical analysis showed significant correlation between type and grade of VUR. Our data confirmed predominance of VUR in females and in children under the age of 5. Statistically significant correlation between ureteral dilatation and the existence of VUR was found, with relatively high sensitivity (67.2%), specificity (81.4%), and high positive (78.8%) and negative predictive value (70.6%), total diagnostic accuracy of 74.2% in detecting VUR, and significantly increased probability (20 – 25%) of detecting VUR in patients with sonographically confirmed ureteral dilatation.

Conclusion:

Sonographically confirmed ureteral dilatation can be used as a predictor of VUR in children with UTIs, and in combination with other predictors, might find a place in an evidence-based selective strategy in children with suspected VUR.

[Imaging in pediatric urology]

BACKGROUND

For many years, sonography and the intravenous pyelogram (IVP) were the most important examination methods for the evaluation of the urinary tract in children. Both methods have their pros and cons: sonography provides ideal visualization of normal kidneys and the evaluation of the pelvicalyceal system. For detection or exclusion of renal scarring, however, this method is not well suited. It provides no information regarding kidney function.

METHODS

With an IVP, it is possible to evaluate urinary excretion and, thus, indirectly assess kidney function. As this examination method involves radiation exposure and the necessity of a contrast agent, it should be avoided in the examination of children. The CT is an excellent examination method that can diagnose nearly all urological diseases in children or answer urological questions; however, a CT scan applies the highest radiation dose of all discussed methods. For this reason, examination via MRI is of increasing importance in uroradiology. Initially only the T2 sequences for the visualization of the urinary tract in children were applied.

CONCLUSION

The current technical developments as well as the use of the contrast agent gadolinium and the antidiuretic agent furosemide allow an all-in-one evaluation of the kidneys and urinary tract.

Flexible ureteroscopy and lasertripsy (FURSL) for paediatric renal calculi: results from a systematic review

OBJECTIVE

To understand the role, safety and efficacy of flexible ureterorenoscopy and lasertripsy (FURSL) for paediatric renal stones.

MATERIAL AND METHODS

A systematic review was conducted using studies identified by a literature search between January 1990 and March 2014. All English language articles reporting on a minimum of five patients≤18-years old, treated with flexible ureteroscopy and lasertripsy for stone disease were included.

RESULTS

A total of six studies (282 patients) were reported, with a mean age of 7.3 years (range 0.25-17 years). The stone sizes ranged from 1 to 30 mm. The mean stone-free rate across the three studies was 85.5% (range 58.0-93.0%) after initial ureteroscopy, with a postoperative stent inserted in 81.8% (range 66.7-98.0%). There were a total of 35 complications (12.4%), with the most severe complication being a Clavien class III (five ureteral injuries, one urinoma). There were no deaths in any of the studies.

CONCLUSION

The present review shows that FURSL for management of renal calculi in the paediatric population is an effective and safe procedure. To ensure that outcomes keep on improving, these procedures should be undertaken by experienced surgeons who are familiar with the difficulties encountered in the paediatric population.

Lower-dose CT urography (CTU) with iterative reconstruction technique in children - initial experience and examination protocol

BACKGROUND

Conventional X-ray urography is one of the basic imaging techniques in urinary tract diseases in children. CT urography (CTU) employing standard Filtered Back Projection (FBP) reconstruction algorithms is connected with higher radiation dose. Advanced iterative reconstruction techniques enable lowering the radiation dose to the level comparable with conventional X-ray urography with better visualization of the urinary tract. Study protocol and indications for this modified technique should be discussed.

MATERIAL/METHODS

Introduction of iterative image reconstruction techniques allowed to significantly reduce the radiation dose delivered during examinations performed at our Department, including CT examinations of urinary tract in children. During the last two years, CT urography replaced conventional X-ray urography and became the basic imaging technique in our Department. We discuss the study protocol regarding pediatric CTU examinations. The main goal is to receive an optimal image quality at reduced radiation dose.

RESULTS

CTU examinations performed using the standard filtered back projection (FBP) reconstruction technique are associated with radiation doses about 1.5 times higher than those in conventional X-ray urography. Implementation of iterative reconstruction algorithms in advanced CT scanners allow to reduce the radiation dose to a level comparable or even lower than that in X-ray urography. In addition, urinary tract can be evaluated more precisely in multiplanar reformatted (MPR) and volume rendered (VR) images.

CONCLUSIONS

1. Advanced iterative reconstruction techniques allow to reduce radiation dose in CT examinations and to extend indications for CT urography in children. 2. Urinary tract can be evaluated more precisely in multiplanar reformatted and volume rendered images. 3. CTU may replace conventional X-ray urography in children.

[Magnetic resonance urography in pediatric urology]

Magnetic resonance urography (MRU) provides high resolution imaging of the urogenital system and the use of paramagnetic contrast agents enables a functional depiction. This review summarizes existing data concerning this diagnostic procedure in pediatric urology. A systematic search and assessment of the literature was performed.A total of 12 studies were reviewed in detail. In mostly small study populations a great heterogeneity concerning methodology, use of comparative examinations and standards of reference was noted. Besides the quality of anatomical imaging, the functional study of renal excretory function and differential renal function was also assessed. Only a few studies performed statistical analyses.The authors' rating of MRU was mostly positive. Due to methodical weaknesses, lack of independent standards of reference and statistical analyses the overall level of evidence was low. Further high quality studies will be necessary to assess the value of MRU for the diagnostic workup in pediatric urology.

A case of complete renal duplex with h-shaped ureter

We present a case of complete renal duplex with H-shaped double ureter opening into the bladder with 2 separate orifices. It is an extremely rare variety of renal duplex which was reported only once in the literature. Fifty-four-year-old male presented to our department with right renal pain. Noncontrast CT revealed stone midthird right ureter with duplex right kidney. Retrograde ureteropyelography and ureteroscopy revealed this rare anomaly.

Multi-detector CT in the paediatric urinary tract

The use of paediatric multi-slice CT (MSCT) is rapidly increasing worldwide. As technology advances its application in paediatric care is constantly expanding with an increasing need for radiation dose control and appropriate utilization. Recommendations on how and when to use CT for assessment of the paediatric urinary tract appear to be an important issue. Therefore the European Society of Paediatric Radiology (ESPR) uroradiology task force and European Society of Urogenital Radiology (ESUR) paediatric working groups created a proposal for performing renal CT in children that has recently been published. The objective of this paper is to discuss paediatric urinary tract CT (uro-CT) in more detail and depth. The specific aim is not only to offer general recommendations on clinical indications and optimization processes of paediatric CT examination, but also to address various childhood characteristics and phenomena that facilitate understanding the different approach and use of uro-CT in children compared to adults. According to ALARA principles, paediatric uro-CT should only be considered for selected indications provided high-level comprehensive US is not conclusive and alternative non-ionizing techniques such as MR are not available or appropriate. Optimization of paediatric uro-CT protocols (considering lower age-adapted kV and mAs) is mandatory, and the number of phases and acquisition series should be kept as few as possible.

[Serial voiding urosonography: a safe technique for the study of the entire urinary tract in children]

For more than a decade, serial voiding urosonography has been one of the imaging modalities used to detect vesicoureteral reflux in children and it is now also used to study the urethra. The main advantage of this technique is it does not irradiate. Given the important recognition of serial voiding urosonography by the European Society of Pediatric Radiology at the last congress in May 2011, we think it is useful to describe how to carry out this technique successfully. In this update on serial voiding urosonography, we describe the indications, the entire procedure, and the different characteristics of this technique, which we understand will soon become the technique of choice for screening for vesicoureteral reflux as well as for urethral pathology in children.

Voiding urosonography including urethrosonography: high-quality examinations with an optimised procedure using a second-generation US contrast agent

BACKGROUND

Voiding urosonography (VUS) is established as a technique for detecting vesicoureteral reflux in children.

OBJECTIVE

To evaluate the quality of images of the entire urinary tract when using a second-generation US contrast agent and a modified VUS technique.

MATERIALS AND METHODS

We evaluated 307 VUS examinations performed using SonoVue® in 591 pelvi-ureter units in 295 children of mean age, 27.1 (S.D., 42.5) months, with 154 (50.2%) of the examinations performed in boys; 58 children also underwent VUS using Levovist®. Three criteria were used for quality assessment of the bladder image: (1) progressive incorporation of contrast material in the bladder, (2) homogeneous bladder-filling to maximum capacity, and (3) visualisation of the posterior bladder wall.

RESULTS

Criterion 1 was fulfilled in 305 (99.3%), criterion 2 in 304 (99%) and criterion 3 in 304 (99%) studies. In children who underwent VUS with both contrast agents, the concordance between the two techniques was moderate for findings in the bladder (Cohen K = 0.487; P < 0001) and perfect for findings in the male urethra.

CONCLUSION

By a modified technique we obtained high-quality images of the bladder with the second-generation contrast agent.

Magnetic resonance urography in duplex kidney with ectopic ureteral insertion

This is a report on the use of magnetic resonance urography (MRU) in a 6-year-old girl who presented with urinary incontinence. She had a left duplex kidney with poorly functioning upper moiety and ectopic insertion of the dilated upper pole ureter. MRU has been shown to be superior to conventional imaging techniques in delineating poorly functioning moieties of duplex kidneys and ectopic ureters.