Podcast: The accuracy of two imaging tests in detecting vesicoureteral reflux

There is considerable interest in detecting vesicoureteral reflux in children, a condition in which urine can flow backwards from the bladder to the kidney, and cause kidney damage. It can be diagnosed with a test called a voiding cystourethrogram, but this is invasive and exposes children to x-rays. It’s important therefore to find other accurate methods and a new Cochrane Review from July 2016 evaluated two possible alternative imaging tests as ways to identify children who have vesicoureteral reflux and are at higher risks of long-term kidney damage, but with less discomfort and radiation than a voiding cystourethrogram. The review was done by Dr. Nader Shaikh and colleagues from the University of Pittsburgh, Pennsylvania in the USA. In this evidence pod, his colleague, Dr Stephanie Hum tells us what they found.

- Read transcript

John: Hello, I'm John Hilton, editor of the Cochrane Editorial unit. There is considerable interest in detecting vesicoureteral reflux in children, a condition in which urine can flow backwards from the bladder to the kidney, and cause kidney damage. It can be diagnosed with a test called a voiding cystourethrogram, but this is invasive and exposes children to x-rays. It’s important therefore to find other accurate methods and a new Cochrane Review from July 2016 evaluated two possible alternative imaging tests as ways to identify children who have vesicoureteral reflux and are at higher risks of long-term kidney damage, but with less discomfort and radiation than a voiding cystourethrogram. The review was done by Dr. Nader Shaikh and colleagues from the University of Pittsburgh, Pennsylvania in the USA. In this evidence pod, his colleague, Dr Stephanie Hum tells us what they found.

Stephanie: The main reason we treat urinary tract infection in children is to prevent permanent kidney scarring and kidney failure. This is a particularly severe problem for children who have the congenital abnormality, vesicoureteral reflux, which allows backwards flow of urine from the bladder to the kidney, and can lead to kidney infection and scarring. Clinicians have focused on the identification and treatment of infections among these children because those with severe, high-grade reflux have a higher likelihood of kidney scarring.
The current gold standard for diagnosis of reflux and for grading its severity is a voiding cystourethrogram. During this procedure, the child has their bladder catheterized and radiocontrast material is used to fill the bladder. Fluoroscopy visualizes any movement of the contrast backwards into the ureters, indicating urine reflux. As John said, the invasive nature of this test and the use of x-rays are problematic and it would be good have tests that avoid these problems. And two possible alternatives for assessing risk of urine reflux are dimercaptosuccinic acid (DMSA for short) renal scanning and kidney-bladder ultrasound. DMSA involves an intravenous injection to detect photon-deficient areas in the kidneys caused by earlier pyelonephritis. While ultrasound detects anatomic abnormalities in the kidney.
In our review, we combined information from 42 published studies that compared DMSA scanning, renal-bladder ultrasound or both with cystourethrography in children who had a previously documented urinary tract infection; but have found that neither approach is a satisfactory replacement for voiding cystourethrography.
In 20 studies involving just over 3700 children, ultrasound was not sufficiently accurate to detect reflux or high-grade reflux and we concluded that it is not an appropriate test to rule in or rule out reflux of any severity. In 19 studies among nearly 3900 children, DMSA scanning was not as accurate as cystourethrography for detecting reflux and was limited in its usefulness in ruling out reflux. Although DMSA scanning had high sensitivity for detecting high-grade reflux, using DMSA to rule out high-grade reflux was limited by the test’s low sensitivity. For example, in an average risk population of children with febrile urinary tract infections, the DMSA will be positive in about 70% of children. This means that even though a child with a negative DMSA has a less than 1% possibility of actually having high-grade reflux, screening with a DMSA will lead to many children being incorrectly labelled as at high-risk of reflux.
In conclusion, neither kidney ultrasound nor DMSA scanning are sufficiently accurate to detect vesicoureteral reflux of all grades. They are not appropriate tests to replace voiding cystourethrography for the diagnosis of reflux in children who have urinary tract infections.

John: If you would like more information about this review and the included studies, simply visit Cochrane Library dot com and search for ‘children and screening for reflux’.

Hello, I'm John Hilton, editor of the Cochrane Editorial unit. 

Close transcript
Share/Save