Vesicoureteral Reflux

Overview.

Vesicoureteral reflux (VUR) refers to the retrograde passage of urine from the urinary bladder into the ureter and often to the renal collecting system. VUR mainly affects infants and young children with a prevalence of 25% to 40% ( Box 119.1 ). VUR is a risk factor for the development of pyelonephritis, with consequent renal scarring.

Current evidence suggests that the long-term risks associated with pyelonephritis and renal scarring are low and that preventive antibiotics and surgery may be useful in only a subset of patients. Therefore most children with an uncomplicated initial urinary tract infection (UTI) will not benefit from imaging, and the focus in the evaluation of VUR should be patients who have complicated or recurrent UTIs, as some of them may benefit from prophylactic antibiotics or surgery. Another common indication in the evaluation of VUR is prenatal hydronephrosis. VUR may also be associated with anomalies that require prompt surgical treatment to prevent renal damage.

Overview.

The etiology of VUR is not entirely understood. It is possible that VUR in some infants is physiologic and will spontaneously resolve. VUR may be caused by abnormal ureteric budding or interaction with the metanephric mesenchyme, resulting in a lateralized ureteral orifice, with a subsequent shortened submucosal ureter that is deficient in longitudinal muscle fibers. Primary VUR has a familial association with genetic heterogeneity.

Secondary VUR is seen in patients with other urinary tract anomalies ( Box 119.2 ). In addition, increased bladder pressure from bladder outlet obstruction (e.g., posterior urethral valves), as well as increased detrusor muscle tone or uncoordinated bladder contraction (e.g., neurogenic bladder) can cause VUR.

Overview.

The diagnostic imaging modalities preferred for the evaluation of VUR include voiding cystourethrogram (VCUG), radionuclide cystography (RNC), and ultrasound (US) ( Box 119.3 ). The optimal imaging modality in the assessment of VUR depends on the indication, radiologist preference and experience, and availability. VCUG is the gold standard for depicting VUR and is especially useful as the initial imaging examination for boys, while contrast-enhanced voiding urosonography (ce-VUS) involves no ionizing radiation and may be used as the first study in girls and in follow-up studies. In the past, RNC was considered to have lower levels of ionizing radiation compared with VCUG; however, with the use of modern fluoroscopy techniques, VCUG has been found to result in significantly lower radiation dose.