State-of-the-Art Renal Imaging in Children Bernarda Viteri, MD,a,b,c Juan S. Calle-Toro, MD,b Susan Furth, MD,a,c Kassa Darge, MD,b,c Erum A. Hartung, MD,a,c Hansel Otero, MDb,c Imaging modalities for diagnosing kidney and urinary tract disorders in abstract children have developed rapidly over the last decade largely because of advancement of modern technology. General pediatricians and neonatologists are often the front line in detecting renal anomalies. There is a lack of knowledge of the applicability, indications, and nephrotoxic risks of novel aDivision of Nephrology, Department of Pediatrics and renal imaging modalities. Here we describe the clinical impact of congenital bDivision of Body Imaging, Department of Radiology, Children’s Hospital of Philadelphia, Philadelphia, anomalies of the kidneys and urinary tract and describe pediatric-specific Pennsylvania; and cDepartment of Pediatrics, Perelman renal imaging techniques by providing a practical guideline for the diagnosis School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania of kidney and urinary tract disorders. Drs Viteri and Otero conceptualized and designed the manuscript, coordinated data and images collection, analyzed data, and drafted and revised fi 4 the nal manuscript; Drs Darge and Furth Renal imaging continues to evolve with CAKUT. CAKUT constitutes 20% contributed to the design of the manuscript and rapidly. From advances in conventional to 30% of all anomalies identified in the critically reviewed the manuscript for important kidney ultrasound to quantitative prenatal period and occurs in up to intellectual content; Drs Calle-Toro and Hartung imaging evaluation, new technologies 60% of children with chronic kidney participated in the design of the manuscript and are transforming how we assess kidney disease (CKD) in the postnatal critically reviewed the manuscript for important 1,2,5 intellectual content; and all authors approved the function and disease. Congenital period. Common types of CAKUT final manuscript as submitted and agree to be anomalies of the kidney and urinary result from failure of normal nephron accountable for all aspects of the work. tract (CAKUT) are the most common development (renal dysplasia, renal DOI: https://doi.org/10.1542/peds.2019-0829 cause of end-stage renal disease in agenesis, and multicystic renal Accepted for publication Aug 5, 2019 children and, consequently, the most diseases), abnormalities of embryonic common cause of the need for renal migration of the kidneys (ectopic Address correspondence to Bernarda Viteri, MD, Division of Nephrology, Department of Pediatrics, replacement therapy, such as dialysis, kidneys and horseshoe kidneys), and Children’s Hospital of Philadelphia, 3500 Civic Center 1,2 in this patient population. As a result, abnormalities of the developing urinary Blvd, Buerger Center, 9th Floor, Philadelphia, PA imaging is crucial for early detection of collecting system (vesicoureteral reflux 19104. E-mail: [email protected] kidney and urinary tract disease, [VUR], ureteropelvic junction PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, monitoring of kidney function, and obstruction, lower urinary tract 1098-4275). enhancing the assessment of disease obstruction, etc). CAKUT often presents Copyright © 2020 by the American Academy of progression and prognosis. with urinary tract dilation (UTD), Pediatrics Conventional methods for the diagnosis previously referred to as FINANCIAL DISCLOSURE: The authors have indicated of renal dysfunction based on clinical hydronephrosis.6,7 they have no financial relationships relevant to this chemistry measurements (such as article to disclose. serum creatinine level) have been Although hydronephrosis remains FUNDING: Supported by National Institutes of Health shown to be suboptimal for early a commonly used term, it often has grant T32DK007006 (principal investigator Lawrence detection of functional loss.3 different meanings among Holzman). Funded by the National Institutes of Health practitioners. In 2014, a unified (NIH). CAKUT includes a variety of disorders consensus reached among multiple POTENTIAL CONFLICT OF INTEREST: The authors have that arise during the development of professional societies recommended indicated they have no potential conflicts of interest the kidneys, ureters, bladder, and replacing the term hydronephrosis with to disclose. urethra in fetal life. Although CAKUT the more specific descriptor UTD to tends to present sporadically, denote an imaging finding in a system To cite: Viteri B, Calle-Toro JS, Furth S, et al. associated anomalies have been that may or may not be under pressure State-of-the-Art Renal Imaging in Children. Pediatrics. 2020;145(2):e20190829 described in up to 30% of infants born (ie, obstructive versus nonobstructive Downloaded from www.aappublications.org/news by guest on October 2, 2021 PEDIATRICS Volume 145, number 2, February 2020:e20190829 STATE-OF-THE-ART REVIEW ARTICLE UTD).8 Antenatal and postnatal UTD armamentarium of pediatric renal renal imaging modalities with an each have their own scoring system imaging. Emerging technologies that emphasis on novel techniques and for reference (Fig 1).8 Higher scores are increasingly being used in clinical their potential clinical value in the relate to a higher degree of dilatation settings include functional magnetic detection and monitoring of children and renal parenchymal, ureteral, and/ resonance urography (fMRU), with kidney disease. or bladder abnormalities that require contrast-enhanced ultrasound further workup and monitoring.9 (CEUS), and contrast-enhanced ANATOMIC IMAGING voiding ultrasound, which can There is currently no single gold delineate anatomy at a higher Ultrasound standard to assess obstructive resolution and provide functional, Renal and bladder ultrasound (RBUS) uropathy in children, and usually, perfusion, and excretion information is the first-line imaging modality for a combination of imaging tests are of the kidneys and urinary tract – evaluation of the renal anatomy in used.10 12 Although renal bladder without using ionizing radiation. children because it is noninvasive, is ultrasound, fluoroscopy, and nuclear Additional techniques that remain broadly available, is relatively fast, medicine functional studies remain under study include three- lacks ionizing radiation, and is less the main tools for anatomic and dimensional (3D) printing, costly than other imaging modalities. functional diagnosis and management elastography, and volumetric analysis. Additionally, ultrasound does not of UTD and CAKUT, novel Our purpose for this article is to require specific patient positioning or technologies have been added to the provide a comprehensive overview of the need to be in a machine, which allows for imaging of children while in supine, prone, semi-upright or upright positions or, in the case of infants, while being held by a caregiver. RBUS depicts kidney size (and growth over time), echogenicity, echotexture, parenchymal thickness, the duplex system, and the degree of dilatation of the pelvocalyceal system and ureters in children.13 RBUS can be used to identify masses and large calculi, can be used to measure pre- and postvoid bladder volumes, and can provide real-time images for guidance of interventional procedures. During basic ultrasound imaging, the kidney may be divided into an outer cortex and an inner medulla. The cortex is composed of an outer rim of tissue as well as columns of cortical tissue that descend between the medullary pyramids (Fig 2A). These columns have been termed the septal cortex, also commonly referred to as FIGURE 1 columns of Bertin (Fig 3). The Postnatal UTD classification and recommendations with grayscale ultrasound representative medulla is composed of a variable examples. Postnatal presentation for UTD P1, low risk; UTD P2, intermediate risk; UTD P3, high risk. number of renal pyramids, with the fi fi fi Classi cation is based on the most signi cant ultrasound nding. For example, if the anterior- base of the pyramid formed by its posterior renal pelvis diameter is found within UTD P1 range, but there is peripheral calyceal dilation, then the correct classification is UTD P2. a Calyceal dilation and ureteral dilation are often overlying renal cortex and its apex by present in patients with UTD P3 but are not needed to qualify for UTD P3 if there is UTD with either the renal papilla that projects into abnormal parenchymal thickness, abnormal parenchymal appearance, or abnormal bladder. a minor calyx. The papillae are cone- Adapted from Nguyen HT, Benson CB, Bromley B, et al. Multidisciplinary consensus on the classifi- cation of prenatal and postnatal urinary tract dilation (UTD classification system). J Pediatr Urol. shaped structures that contain the 2014;10(6):982–998 and Chow JS, Koning JL, Back SJ, Nguyen HT, Phelps A, Darge K. Classification of openings of the collecting ducts, pediatric urinary tract dilation: the new language. Pediatr Radiol. 2017;47(9):1109–1115. which empty into the calyces. A calyx Downloaded from www.aappublications.org/news by guest on October 2, 2021 2 VITERI et al and it decreases imaging time by requiring a single sweep with reconstruction in multiple planes at a later time.19,20 Therefore, interest now lies in supporting quantitative imaging analysis, such as automated segmentation of the kidneys and urinary tract, to enhance the care of children with UTD. Given parenchymal volume calculations from 3DUS are comparable to those from dimercaptosuccinic acid scintigraphy