New Renal-Imaging Modalities Help Diagnose Congenital Anomalies Early

By Will Boggs MD

January 09, 2020

NEW YORK (Reuters Health) - State-of-the-art renal imaging facilitates the early diagnosis of congenital anomalies of the kidney and urinary tract (CAKUT), according to a review.

CAKUT make up 20% to 30% of all anomalies identified in the prenatal period and occur in up to 60% of children with chronic kidney disease in the postnatal period. CAKUT often present with urinary tract dilation (UTD).

Renal bladder ultrasound, fluoroscopy, and nuclear-medicine functional studies remain the main tools for the anatomic and functional diagnosis and management of UTD and CAKUT, but over the past decade new technologies have been added to the pediatric renal-imaging toolbox.

Dr. Bernarda Viteri of Children's Hospital of Philadelphia and colleagues provide a comprehensive overview of these technologies and their clinical value in their new report in Pediatrics.

Three-dimensional ultrasound (3DUS) provides volumetric evaluation and more complete visualization of the collection system, and its emergence could result in decreased use of CT, MRI, and diuretic renography.

Shear-wave elastography, another advanced ultrasound technique, noninvasively measures tissue stiffness and has potential clinical use in the assessment of chronic kidney disease, kidney allograft, and vesicoureteral reflux (VUR).

Contrast-enhanced ultrasound (CEUS), which uses microbubbles as an intravenous ultrasound contrast agent, is more sensitive than Doppler in detecting perfusion abnormalities. It can detect early features of allograft dysfunction in the setting of acute tubular necrosis, rejection, cortical necrosis and other vascular complications. It is most promising for evaluating focal renal disease, the authors say.

Contrast-enhanced voiding urosonography (CeVUS) is a radiation-free alternative to the gold-standard fluoroscopic voiding cystourethrography (VCUG) for evaluating VUR and urethral pathology. CeVUS has greater sensitivity than VCUG for the detection of clinically significant VUR.

3D-printing models have shown high accuracy in revealing complex anatomic structures and pathologies, and models of kidneys with renal tumors have been reported to enhance the understanding of surgeons, trainees, and patients and their families regarding the goals of surgery.

Nuclear-medicine functional renal scans can use different radiotracers to assess glomerular filtration, tubular secretion, or cortical tubular binding, whereas functional MR urography (fMRU) provides a comprehensive morphologic and functional evaluation of the urinary tract in a single, radiation-free examination and is becoming the test of choice in patients with complex anatomy.

The review contains a useful table of these imaging modalities that includes, among other features, their duration, common clinical indications, potential nephrotoxicity and relative cost.

Dr. Andrew Schwaderer of Indiana University School of Medicine, in Indianapolis, who recently reviewed the diagnosis and imaging of neonatal urinary-tract infections, told Reuters Health by email, "Our goals with pediatric kidney imaging include obtaining an accurate diagnosis, avoiding or limiting radiation exposure, using the study with minimum amount of risk (contrast risk, anesthesia risk, etc.), limiting patient discomfort, and limiting expense to families and the health care system."

"In the long term," he added, "emerging technologies such as CEUS, CeVUS and fMRU provide new options that will assist clinicians in obtaining these goals. In the short term, having new options adds a layer of complexity that will require clinicians to go over risk and benefits of different imaging modalities with patients and families."

"When a child requires renal imaging, it will be important to balance the risk versus benefits of several imaging modalities," said Dr. Schwaderer, who was not involved in the new work. "The expanding imaging modalities will likely concentrate pediatric renal imaging in specialized pediatric institutions for the short-term."

He added, "It only received passing mention in the article, but in my judgment low-radiation CTs warrant comment because they are more readily available than many of the mentioned technologies. If a pediatric-age patient needs a CT of the kidney or urinary tract, a low-radiation option should be considered."

SOURCE: Pediatrics, online January 8, 2020.