VESICOURETERIC REFLUX DIAGNOSIS

Vesicoureteric reflux
Vesicoureteric reflux, the retrograde passage of urine from the bladder up the ureter and into the kidney, predisposes the child to urinary tract infection and the development of reflux nephropathy. In the first year of life only, reflux is more common in boys than in girls and is usually more severe. Conversely, after the first year of life reflux is more likely to present in girls and is often less severe.

Vesicoureteric reflux is a common cause of hydronephrosis antenatally, accounting for up to 38% of all prenatal urinary tract dilatations, requiring ultrasound follow-up and antibiotic prophylaxis. Reflux may either be due to a developmental anomaly at the vesicoureteric junction, or the result of a neurogenic bladder, partial outlet obstruction or foreign bodies such as calculi and the presence of a catheter. Children who have had one or more episodes of urinary tract infection should be investigated to search for an underlying cause and to identify evidence of reflux nephropathy. Approximately 2% of boys and 8% of girls will develop at least one urinary tract infection by 10 years of age, requiring investigation, and in most centres will account for a substantial proportion of the paediatric sonography performed.

Reflux itself is not reliably diagnosed by ultrasound as it is possible to have intermittent reflux in the presence of a normal ultrasound scan, with a non-dilated urinary tract. There may be evidence of thickening of the uroepithelium of the renal pelvis due to intermittent renal pelvis distension. Uni- or bilateral dilatation may be present to a mild or severe degree and may involve the kidney and/or ureter. It is important to scan the renal pelves and ureteric orifice immediately after micturition, when intermittent dilatation due to reflux may be demonstrated on an otherwise normal scan. When dilatation is seen, the exact cause may be uncertain unless reflux is actually visualized, which is rare, and micturating cystography is required.

Although most commonly performed conventionally by fluoroscopy using iodinated contrast medium, radionuclide cystography and more recently contrast sonocystography have been used as an alternative, particularly in the older child. The most common complication of reflux is infection and most children present with at least one episode of urinary tract infection. This can cause renal scarring. It is important to make the diagnosis of vesicoureteric reflux and renal scarring early in order to prescribe prophylactic antibiotics in an attempt to avoid the damaging complications caused by reflux of infected urine.

The ultrasound appearances of scarring include a focal reduction in cortical thickness, irregular outline, interruption of or loss of the renal capsule echo or a disruption in the renal architecture. Colour flow and power Doppler may show triangular areas of decreased or absent blood flow (and occasionally increased flow) and can improve the detection rate of focal scarring on sonography. These signs can be difficult to demonstrate in young childrens kidneys, particularly when highly lobulated, and the most reliable method of scar detection is a DMSA scan.

Chronic reflux nephropathy leads to failure of renal growth, resulting in a shrivelled, poorly functioning kidney. Measurements of the maximum length of the kidneys should be routinely performed, and can be related to age, height and weight. A difference in renal length of more than 10% between the two kidneys should prompt further investigation into renal function with a DMSA scan.