Test Combination Spares Children from Voiding Cystourethrography

A combination of two tests can spare children from having to undergo the discomfort of voiding cystourethrography (VCUG) after a first-time febrile urinary tract infection, according to new study.

Researchers at the Federal University of Minas Gerais (Brazil) examined 533 children following a first urinary tract infection. The patients were assessed by three diagnostic imaging studies: renal ultrasound, dimercapto-succinic acid (DMSA) renal scintigraphy, and voiding cystourethrogram (VCUG). The main event of interest was the presence of a high-grade (dilating) vesicoureteral reflux (VUR). The combined and separate diagnostic accuracy of the screening methods was assessed by calculation of diagnostic odds ratio (OR), sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio.

The results showed that 246 of the patients had a VUR, of whom 144 (27%) had high-grade disease. The sensitivity, negative predictive value, and diagnostic OR of ultrasound for high-grade reflux were 83.3%, 90.8%, and 7.9, respectively. DMSA renal scintigraphy had the same sensitivity as ultrasound, but a higher negative predictive value (91.7%) and diagnostic OR (10.9). If both tests were analyzed in parallel by using the OR rule--i.e., a negative diagnosis was established only when both test results were normal--the sensitivity increased to 97%, negative predictive value to 97%, and diagnostic OR to 25.3. The researchers found that only nine children (6.3%) with dilating VUR had an absence of alterations in both tests. The study was published they reported online on November 15, 2010, in the Journal of Urology.

"Reducing the number of voiding cystourethrography exams would be of great value, since it is an unpleasant procedure that is extremely traumatic for some children and their parents,” concluded lead author Isabel Quirino, MD, and colleagues. "Ultrasound and dimercapto-succinic acid scan used in combination are reliable predictors of dilating vesicoureteral reflux.”

VCUG is a technique for watching a person's urethra and urinary bladder while the person urinates (voids). The technique consists of catheterizing the person in order to fill the bladder with a radiopaque contrast agent; under fluoroscopy, the radiologist watches the contrast enter the bladder and looks at the anatomy of the patient. If the contrast moves into the ureters and back into the kidneys, the radiologist makes the diagnosis of VUR, and gives the degree of severity a score. The exam ends when the person voids on the table while the radiologist is watching under fluoroscopy; it is important to watch the contrast during voiding, because this is when the bladder has the most pressure, and it is most likely this is when reflux will occur.

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Federal University of Minas Gerais