Vesico-ureteric reflux [VUR] is an abnormal reverse flow of urine from the bladder back to the kidneys. VUR is the most common urological problem associated with urinary tract infection (UTI) in children. Most of the VUR cases are congenital (primary); however, they can occur following conditions causing bladder outlet obstruction (secondary).
1. How Common Is VUR?
It is seen in almost one-third of children presenting with urinary infection (UTI) symptoms and also in 1- 2% in the general population. In infants, the incidence is much higher among boys, while in older children the incidence is reported to be higher among girls.
2. Why Does VUR Occur in Some Children?
During voiding or micturition, the urinary bladder contracts, while the bladder outlet is closed raising the pressure within the bladder. The oblique insertion of ureters into the urinary bladder creates a submucosal tunnel that closes with the raised bladder pressure during voiding and thereby prevents the urine from flowing back into the ureters. This structural anatomy is altered in children with VUR and therefore urine refluxes into either one or both the ureters.
3. What Causes VUR?
It is still unclear what exactly causes VUR. The basis for VUR is thought to be genetic. 30-50% of first-degree relatives of VUR patients are diagnosed to have VUR. The risk is highest among the siblings of VUR patients diagnosed before 3 years of age. Studies from Dublin, Ireland where VUR has been studied in detail, recommend screening all siblings of patients with high grades (III to V) of VUR.
Most of the VUR cases are primarlly with a congenital pathology. However, VUR can be secondary due to raised or dysfunctional bladder pressures as seen in urological conditions like posterior urethral valves, bladder diverticulum, neuropathic bladder and voiding dysfunction syndromes. Ectopic ureters are usually associated with ureterocele and duplex system, which can also lead to significant VUR.
4. What Are the Symptoms and Signs of VUR?
VUR by itself does not produce any clinical signs and symptoms and therefore most children and infants with VUR are asymptomatic. However, urine infections (UTI) occur commonly in VUR patients and may present with urinary symptoms such as painful voiding or burning sensation on voiding, blood-stained urine, cloudy urine, frequent voiding, an urgency to pass urine and dribbling urine. Patients can also have fever, vomiting and loin pain.
VUR should be suspected in all infants and younger children presenting with febrile urine infection (UTI) or recurrent urine infections.
5. What Tests Are Done for VUR?
The NICE guidelines from the UK recommend that all children presenting with urine infection (UTI) under the age of 6 months should undergo an ultrasound scan (USS) and micturating cysto-urethrogram (MCUG) and a DMSA scan.
Ultrasound scan (USS) is a valuable non-invasive test that can reveal dilatation of the kidney and urine collecting system. Urinary bladder volumes before and after voiding can be calculated and these help in diagnosing bladder dysfunction, which could be the underlying cause of VUR. Impaired kidney growth and scarred kidneys can also be picked up on ultrasound scan (USS).
VUR is diagnosed on MCUG (micturating cysto-urethrogram) scan and it is the gold standard diagnostic test. Compliance is an issue in children; but infants tolerate the procedure well. MCUG not only diagnoses VUR but also grades the VUR and also provides valuable information on the bladder neck and urethra and thus identifies any obstruction or secondary causes of VUR.
Nuclear renal imaging involves the injection of radio-isotope material and obtaining images at various intervals. DMSA scan is most commonly done in these patients and this test provides information on kidney function and shows kidney scarring. Timing of these scans is particularly important and should not be carried out within the first 3 months immediately after a urine infection (UTI). If done earlier, results may be inaccurate.
6. How Is VUR Diagnosed?
The MCUG (micturating cystourethrogram) scan is the standard diagnostic test for VUR worldwide. The scan involves putting a tube (a catheter) into the urethra (urine pipe) and an injecting dye (contrast) to fill the urinary bladder and taking X-ray images whilst the patient voids. As per the MCUG scan, VUR is graded into 5 grades.
7. What Are the Complications of VUR?
The most worrying outcome of VUR is reflux nephropathy [RN]. Patients with VUR may develop scarred kidneys and impaired growth of kidneys, collectively called reflux nephropathy [RN]. Reflux nephropathy leads to loss of kidney function and high blood pressure (hypertension). A combination of urine infection (UTI) with high grade VUR is known to cause RN.
8. How to Treat VUR in Children?
In infants and younger children, the submucosal tunnel of ureter is short and straighter, but as the children grow, the length of the tunnel increases and so the bladder pressure decreases. This change possibly explains the spontaneous resolution of VUR in some children. Low grades of VUR (grades 1 and 2) are most likely to resolve and will only need observation. The grade of reflux is the strongest predictor of VUR resolution, with high-grade VUR being much less likely to resolve on its own.