Urogenital ImagingReflux, vesicoureteric
the retrograde passage of urine from the bladder into the
ureter. This is abnormal, because the normal vesicoureteric reflux junction acts as a one-way valve, allowing the normal antegrade passage of urine into the bladder, but preventing flow in the reverse direction. Vesicoureteric reflux may be primary or secondary. Primary vesicoureteric reflux is common in childhood, and is believed to be due to a developmental deficiency in the muscle layer of the ureterotrigonal region. Familial cases have been described. Other
congenital causes of vesicoureteric reflux include complete ureteric duplication (reflux typically occurs into the
ureter of the lower pole moiety), ectopic
ureter, prune belly syndrome, and
congenital (Hutch) periureteric diverticulum (see
congenital bladder diverticulum). Acquired causes include bladder wall oedema or
fibrosis, prostatectomy, bladder neck incision, and ureteric reimplantation. Vesicoureteric reflux is a potentially serious condition, because it may lead to
renal damage by allowing reflux of infected urine from the bladder to the kidney, which results in
pyelonephritis, or by allowing transmission of bladder voiding pressures to the kidneys, causing
hydronephrosis. Resulting
renal disease is known as
reflux nephropathy. Patients may present with pyelonephritis, cystitis or uraemic symptoms. Asymptomatic pyelonephritis may be discovered as an incidental finding on routine urinalysis.
The incidence of vesicoureteric reflux in healthy children is under 1%, but is 20 - 50% in children with urinary tract infection. The definitive test for the diagnosis of reflux is conventional contrast cystography (Fig.1). Films are taken during bladder filling, during voiding and after voiding.
An international grading system has come into general use for the assessment of the severity of reflux, which allows objective comparison of therapeutic modalities. In grade I reflux, contrast refluxes into the ureter only, opacifying part (IA) or all of the ureter. In the latter case, the ureter may be of normal calibre (IB) or dilated (IC). In grade II reflux, contrast reaches the renal pelvis, which is not dilated. Ureteric opacification may be incomplete (IIA), incomplete with focal dilatation (IIB), or complete (IIC). In grade III reflux, contrast reaches the renal pelvis, with mild dilatation of the ureter and pelvicaliceal system (IIIA), or moderate dilatation with early forniceal blunting (IIIC). In grade IV reflux, there is moderate pelviureteroectasis, with obliteration of the forniceal angles but preservation of the papillary impressions. The forniceal angles may be partially (IVA) or completely obliterated. In the latter case, the ureter may be tortuous (IVB) and there may be extensive pelviectasis (IVC). In grade V reflux, there is moderate to severe pelviureteroectasis, with near complete (VA) or complete obliteration of the papillary impressions. The latter may be associated with severe (VB) or extreme (VC) collecting system dilatation. Reflux may also be demonstrated by voiding radionuclide cystography; it is sometimes detected by US (Fig.2). Vesicoureteric reflux may be unilateral, bilateral or intermittent. Children with lower grades of primary vesicoureteric reflux can often be successfully managed with medical treatment, with spontaneous resolution as they grow up. Other children may require surgery.
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