Potential of modern sonographic techniques in paediatric uroradiology

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.

[The role of contrast-enhanced pulse inversion harmonic imaging (CEUS) and contrast-enhanced computed tomography (CECT) in the preoperative diagnosis of renal lesions]

OBJECTIVE

The preoperative assessment of structural and functional changes in renal tumors using contrast-enhanced pulse inversion harmonic imaging (CEUS) and contrast-enhanced computed tomography (CECT).

MATERIALS AND METHODS

All consecutive patients referred to two tertiary hospitals for surgery on suspicion of a malignant renal lesion, who had been examined under the predefined study protocol using CEUS and CECT, were prospectively included in the study. All renal lesions suspected of being malignant were subjected to histopathological examination. Lesions expected to be benign were followed up according to the study protocol. The accuracy of CEUS and CECT with the final histology or follow-up results and the statistically significant difference between the two imaging techniques was calculated.

RESULTS

Over a period of 3 years (2008-2011), 68 of 93 patients examined met the study criteria. The prevalence of malignant tumors in the study was 72%. Fifty four (79%) patients underwent surgery and had a histologically confirmed renal tumor (clear cell carcinoma 45, urothelial papillocarcinoma 4, angiomyolipoma 1, oncytoma 3, xanthogranulomatous pyelonephritis 1) and 14 (21%) patients underwent regular follow-up. Specificity, sensitivity and area under the curve (AUC) reached 57.9%, 98% and 0.779 for CEUS and 52.6%, 98% and 0.753 for CECT.

CONCLUSION

The results show that both imaging methods can reliably rule out malignant disease due to absence of enhancement. Taking into consideration that CEUS can be carried out without severe risk or discomfort, it is time to reconsider CEUS as the method of choice for diagnosis, while CECT should be reserved for staging.

Congenital midureteric stricture: challenges in diagnosis and management

Background. Congenital midureteric stricture (MUS) is a rare malformation. We report our experience with five cases seen over a period of 4 years from 2010 to 2014. Materials and Methods. The study was based on the retrospective analysis of five patients diagnosed as having MUS. Diagnosis was suspected after fetal ultrasonography (USG) in one patient and magnetic resonance urography (MRU) in four patients. Retrograde pyelography (RGP) was performed on three patients. The final diagnosis was confirmed during surgical exploration in all the patients. Results. MRU was found to be a good investigation method. It showed the site of obstruction in the ureter in all instances. Intravenous urography detected proximal ureteric dilatation present in two of the patients. RGP delineates the level of stricture and the course of ureter, as shown in our cases. All patients had significant obstruction on the affected side. Four patients underwent ureteroureterostomy, all of whom had satisfactory results. In one patient, ureteric reimplantation was carried out due to distal small ureteric caliber. Conclusion. This rare entity is often misdiagnosed initially as pelviureteric junction obstruction. MRU is an excellent option for the anatomical location and functional assessment of the involved system. At the time of surgical correction of a ureteral obstruction, RGP is a useful adjunct for delineating the stricture level and morphology.

Pediatric uroradiology: state of the art

Recent years have witnessed major strides in imaging modalities, including US and contrast-enhanced voiding urosonography, fluoroscopy, CT and MRI, and these have significantly impacted paediatric uroradiology. The trend is towards reduced or no radiation exposure and combined morphological and functional imaging. This review presents the currently available and recommended modalities in modern paediatric uroradiology practice.

Obstructive diseases of the urinary tract in children: lessons from the last 15 years

Imaging urinary tract obstruction is a common query in paediatric uroradiology. With the advent of a more conservative treatment approach, the task of imaging today is to distinguish as early as possible those kidneys that do not require surgery, from those that will deteriorate and lose function and/or growth potential and thus benefit from surgery. At present, in spite of significant advancements in imaging and the introduction of diuretic paediatric MR-urography, there is still no reliable a-priori pro-futuro assessment. Thus, repeated follow-up imaging is often necessary for monitoring. Imaging usually starts with US; the major additional complementary and more function-oriented tools are diuretic renal scintigraphy and MR-urography. The frequency and timing as well as the detailed protocol vary within institutions, partly because of differences in the criteria that are used for indicating surgery. Intra-venous urography (IVU) for obstruction has practically vanished apart from for a few exceptions, and the "Whitaker" test is today seldom performed, being reserved for complicated cases.

High resolution MR for evaluation of lower urogenital tract malformations in infants and children: feasibility and preliminary experiences

INTRODUCTION

This retrospective study aimed to assess the value of supplementing heavily T2-weighted, high resolution MR-imaging for detailed anatomic assessment in paediatric lower urogenital tract (UGT) malformations.

PATIENTS/METHODS

Sixteen patients (6 male and 10 female, median age=1.8 years, range=0-9 years) with suspected malformations of the lower UGT who were retrospectively identified from the PACS underwent a clinically indicated standard MR-urography study. In order to facilitate a better anatomic assessment of questioned specific lower UGT structures, an additional three-dimensional Constructive Interference in Steady State-sequence (3D-CISS) had been acquired in these patients. The final diagnosis was established by all imaging results and surgical or laprascopic findings. The findings from the CISS-sequence were compared to the results from standard MR-urography for complementary anatomic information and conspicuity.

RESULTS

Diagnostic 3D-CISS image quality was achieved in all patients. The 3D-CISS confirmed an ectopic ureteral insertion in six patients and reliably excluded ectopic insertion in 10 patients, whereas conventional MR-urography showed an ectopic insertion of the ureter in one case. In six patients with retrovesical complex formations (suspicious for an ectopic cystic renal bud or a cystic genital structure) the 3D-CISS showed increased conspicuity scores for image quality.

CONCLUSION

The additional 3D-CISS-sequence increases the diagnostic yield in the pelvis in children with complex malformations of the lower UGT such as ectopic ureteral insertion or suspected cystic renal or genital malformations at only minimal additional time, compared to standard MR-urography.

Vesicoureteric reflux in the adult

Vesicoureteric reflux (VUR) is a well-recognized entity in the paediatric population, but is not well described or understood in the adult population. This is partly explained by the fact that its incidence declines with advancing age. Its diagnosis is, however, still important, with VUR accounting for at least 10% of adult patients with end-stage renal disease. With early detection and careful management, the secondary complications of VUR such as renal failure can be prevented. Imaging plays a major role in the detection and evaluation of VUR in the adult patient. Conventional techniques such as micturating cystourethrograms have now been supplemented by cross-sectional imaging with CT and MRI. In this review article, we comprehensively review the up to date status of imaging the adult patient with VUR and discuss important subgroups of patients such as pregnant and transplant patients.

Imaging of the neonatal genito-urinary tract

OBJECTIVE

To describe imaging of typical conditions and diseases in the neonatal genito-urinary (GU) tract.

METHOD

The use, the applications, and typical findings using standard imaging techniques (e.g., ultrasound, US, voiding cystourethrography, VCUG) are described, with emphasis on technical aspects, indications, and restrictions in neonatal queries. Only basic applications as used in routine clinical work are included, other more sophisticated and advanced imaging techniques such as scintigraphy, MR-urography, genitography or image-guided interventional procedures will only briefly be mentioned.

SUMMARY AND CONCLUSION

Conventional imaging methods are valuable and - particularly in the neonatal GU tract - sometimes irreplaceable. Skillfully used basic imaging techniques, particularly of US (including modern methods such as Doppler sonography, Harmonic imaging or contrast enhanced US), supplemented by fluoroscopy for VCUG can answer most acutely treatment relevant queries. Rarely early scintigraphic studies, genitography, or MRI may become indicated, usually not for establishing the diagnosis, but to collect additional (functional or anatomical) information necessary for deciding on further treatment, or even image guided interventional procedures may become necessary.

Ultrasound imaging of sacral reflexes

OBJECTIVES

To investigate the reliability of examination of the guarding reflex of the pelvic floor by dynamic perineal ultrasonography in children with bladder dysfunction and in controls.

METHODS

A total of 40 patients with nonneurogenic bladder/sphincter dyssynergia, 40 with spina bifida, and 40 controls underwent a dynamic ultrasound examination of the pelvic floor while coughing and while being tapped on the abdominal wall. The reflex action of the puborectal muscle in females, and the combined action of the puborectal muscle and external sphincter muscle in males, were recorded.

RESULTS

Of the 40 patients with nonneurogenic bladder/sphincter dyssynergia, 38 had a normal reflex action of the puborectal muscle during the abdominal tap and 36 had a normal reflex action when coughing. Two of these patients had unexplained underactive bladder syndrome and were using clean intermittent catheterization, and two could not be assessed because of hypermobility of the bladder neck when coughing but had a normal reaction during abdominal tapping. Of the 40 patients with spina bifida, none had puborectal activity during coughing and 5 had some puborectal activity during tapping. Of the 40 controls, 39 had normal reflex activity during both coughing and tapping.

CONCLUSIONS

The question of whether a child has nonneurogenic or neuropathic bladder/sphincter dysfunction is often difficult to answer on the basis of urodynamic studies alone. Dynamic perineal ultrasound recording of the S2-S4 reflex arches provides reliable additional information and is noninvasive to the patient.

[Modern imaging technology for childhood urinary tract infection]

Imaging in childhood urinary tract infection (UTI) is still a matter of debate. There are established guidelines, however new knowledge and the changed medical environment have enhanced this ongoing discussion. These new insights have impacted therapy and consequently the imaging algorithm. Modern imaging methods -- particularly MRI and modern ultrasound (US) -- are less invasive with a lower radiation burden. Additionally, it has been shown that VUR is a poor predictor for renal scarring out, which affects long-term results. Furthermore, the majority of UT malformations is depicted by prenatal US. The most crucial aspect of improving long-term outcome appears to be the early and reliable depiction of UTI and effective treatment to prevent renal scarring. This review tries to present this new knowledge and to discuss the potential of modern imaging. Recent changes in imaging algorithms are highlighted and an outcome-oriented algorithm that addresses these recent developments is proposed, without lightly abandoning established standards. It consists of an orienting US and -- for depiction of renal involvement -- amplitude coded color Doppler sonography or renal static scintigraphy (considered the gold standard, particularly for evaluating scars); in future MRI may play a role. Based on this concept, only patients with renal damage as well as patients with complex urinary tract malformations or intractable recurrent UTI may have to undergo VCUG.

Modern pediatric ultrasound: potential applications and clinical significance. A review

After the introduction of ultrasound (US), the new imaging modality was first warmly welcomed, but then lost reputation and importance particularly in radiology leading to an increasing number of other -- particularly computed tomography (CT) -- investigations, which especially in pediatrics was a potentially dangerous development considering the radiation hazards. However, innovative and creative US approaches as well as new US techniques such as amplitude-coded color Doppler, harmonic and high-resolution imaging, and US contrast media or three-dimensional US have been introduced over the past decade and significantly broadened the potential of US. Thus, now, the role of US has been widened in many conditions and queries, and US today may well play a more pronounced and essential role in modern imaging algorithms at still relatively low cost, with sufficient diagnostic accuracy and conspicuity. Particularly in the pediatric setting, these new capabilities are applicable in many queries and almost all body regions and should be used to reduce the number of more invasive or radiating and relatively costly examinations that often additionally need some sedation or intravenous iodinated contrast material. To readily provide this approach for sick children, we need to promote the knowledge about modern US capabilities, to train US staff to guarantee 24-h availability of adequate pediatric US performance, and to make it known to the referring clinicians.

Three-dimensional extended field-of-view ultrasound

Three-dimensional (3-D) extended field-of-view ultrasound creates a mosaic view from a set of volumes acquired from a dedicated 3-D ultrasound machine combined with a position tracker. A simple compounding technique can be used to combine the volumes together using only the position measurements, but some misalignment remains. Two different registration methods were developed to correct these errors in the overlapping regions. The first method divides the overlap into smaller blocks and warps the blocks to best align the features. The second method is similar, but uses rigid body registration of the blocks. Experiments in vitro and in vivo showed that block-based registration with warping produced the most reproducible results and the greatest increase in similarity among the overlapping regions. It also produced the best reconstruction accuracy, with a mean distance error of 0.4 mm measured across 101.78 mm in a phantom, representing 0.4% error.

Moderne Ultraschalltechniken und ihre Anwendungen am kindlichen Harntrakt

In children ultrasound plays a central role in the diagnostic imaging of the urinary tract. It is used most frequently and as a primary diagnostic option. Consequently, innovations in ultrasound technology and ultrasound contrast media have major impact on pediatric urosonography. Harmonic imaging is a modality that produces artifact-free images with high resolution. It has been shown that harmonic imaging is superior to fundamental mode in many urosonographic indications. Color Doppler is an established imaging modality, but its application for diagnosis of stones in the urinary tract, especially in children, is relatively new. The so-called twinkling sign, a color Doppler artifact at the site where one normally expects the acoustic shadow to be, enhances the conspicuity of the stone. A further development is three-dimensional (3D) ultrasound. It offers better volume measurement of the bladder and kidneys than 2D ultrasound. Contrast-enhanced voiding urosonography has already proven to be a valuable alternative in the diagnosis of vesicoureteral reflux. Thus, a significant decrease of radiation exposure has become possible as it replaces the radiological methods. With the introduction of contrast-specific ultrasound imaging modalities, further improvements in voiding urosonography are emerging.

Sonographic diagnosis of urethral anomalies in infants: value of perineal sonography

OBJECTIVE

To assess the value of urethral sonography including a perineal approach in evaluating urethral anomalies in infants.

METHODS

A radiology database review identified 88 patients (mean age +/- SD, 64 +/- 84 days) who underwent voiding cystourethrography (VCUG) and urethral sonography as part of extended sonography of the urinary tract. Sonographic and VCUG images and reports were reviewed to assess agreement between both modalities for detection of urethral anomalies.

RESULTS

Sonography facilitated the correct diagnosis of all 3 posterior urethral valves. The only urethral diverticulum, the only ectopic ureteric insertion into the urethra, the only urogenital sinus, and the only urethrovaginal fistula were also shown on sonography. In 73 (94%) of 78 cases, sonography correctly showed the absence of anomalies. In 5 infants, sonography could not reliably assess the urethra and showed indirect signs of urethral anomalies; however, these patients had normal urethras on VCUG.

CONCLUSIONS

Our data show that sonography of the urethra is a valuable tool for diagnosis of urethral anomalies. Especially, negative findings on sonography are highly suggestive of the absence of urethral anomalies. Positive or equivocal sonographic findings should indicate VCUG.

[Advances in pediatric sonography]

Advances in the field of ultrasound technology and ultrasound contrast media over the past few years have also brought major improvements to pediatric sonography. Accordingly, contrast-enhanced voiding urosonography has become a valuable alternative in the diagnosis of vesicoureteral reflux. It is possible to achieve significant reduction in radiation exposure replacing the conventional radiologic methods used for reflux diagnosis with contrast-enhanced ultrasound. Through the introduction of harmonic imaging, an ultrasound scanning modality with high spatial and contrast resolution has become available. The modality was initially propagated as one to be applied in difficult-to-scan adults. However, initial experiences in pediatric applications are demonstrating the significant improvement it can bring in the ultrasound image quality, for example, in intestinal ultrasound. A further development is three-dimensional [3D] imaging using ultrasound. 3D-ultrasound not only offers an improvement in diagnosis but also in the acceptance of ultrasound in interdisciplinary work and teaching. The first applications of 3D-ultrasound in pediatrics are focusing on brain ultrasound and volume measurement of the kidneys.

Investigating the newborn kidney: update on imaging techniques

Advances in imaging have resulted in higher-quality resolution. Techniques formerly considered to give pure anatomic information are now providing functional data, but the functions provided are not those typically measured in pathophysiologic terms. Instead, the data provided demand that we incorporate this new information into the understanding of the pathologic processes that confront us in clinical practice. Ultrasound provides information about kidney volume, blood flow velocity and blood flow volume. Radioisotopes can show the ability of the proximal tubules to extract the tracer from the blood as well as the ability of the kidney to clear the tracer into the bladder. Magnetic resonance imaging provides information about water content of the kidney.