8.4 Etiology of VUR

Fig. 8.23 A micturating cystourethrogram showing grade III VUR

•Grade V – Reflux with gross dilation of ureter, pelvis, and calyces, loss of papillary impressions, and ureteral tortuosity (Figs. 8.29, 8.30, and 8.31)

8.4Etiology of VUR

•VUR is prevented by a one way valve like effect at the uretero-vesical junction.

•This is attributed to several factors including:

–The oblique entrance of the ureter into the urinary bladder

–The submucosal tunnel through which the ureter enter into the urinary bladder

–The ureter’s muscular attachments

•Failure of this mechanism will result in retrograde flow of urine.

•VUR is divided into two types based on etiology:

–Primary VUR

–Secondary VUR

•Primary VUR:

–Primary VUR is the most common form of reflux

–It is due to incompetent or inadequate ureterovesical junction (UVJ)

–The exact cause of the defect in primary VUR is unknown

–This may be secondary to an abnormally short intravesical ureteric segment or abnormal surrounding muscles.

–Other factors that contribute to the etiology of primary VUR include:

•The existence of a strong genetic component is supported by the high rate of reflux in relatives of patients with reflux, but the mechanism of transmission is not clear.

•The possibility of urinary tract infection as a cause of VUR is not clear and many think that UTI and VUR are independent variables. Urinary tract infections may cause reflux due to the elevated pressures associated with inflammation.

•Secondary VUR:

–Secondary VUR is reflux that is associated with or caused by an obstructed or poorly functioning lower urinary tract.

–This is seen in children with congenital bladder outlet obstruction and neurogenic bladder (Figs. 8.32 and 8.33).

–More than 50 % of boys with posterior urethral valves have vesicoureteral reflux (Figs. 8.34 and 8.35).

–In these patients, VUR can be unilateral or bilateral

–Other causes include urethral or meatal stenosis

–Bladder instability, neurogenic bladder and non-neurogenic bladder

–Dysfunctional voiding, with its inherent increase in intravesical pressure, is a cause reflux, even in otherwise healthy children.

–The combination of high-pressure voiding and vesicoureteral reflux increases the risk of pyelonephritis beyond that of the child with low-pressure reflux.

–A unique group of children presents with dysfunctional elimination, which consists

Etiology of VUR

•Primary causes of VUR:

–Short or absent intravesical ureter

–Absence of adequate detrusor backing

–Lateral displacement of the ureteral orifice

–Paraureteral (Hutch) diverticulum

•Secondary causes of VUR:

–Cystitis or UTI

–Bladder outlet obstruction (Posterior urethral valve, urethral stricture, meatal stenosis)

–Neurogenic bladder

–Detrusor instability

•Clinical signs and symptoms associated with a febrile UTI in a neonate may include:

–Irritability

–Persistent high fever

–Listlessness

–Infection in infants can manifest as failure to thrive, with or without fever.

–Other features include vomiting, diarrhea, anorexia, and lethargy

•In cases of VUR and febrile UTI associated with a serious underlying urinary tract abnormality, the neonate could present with respiratory distress, failure to thrive, renal failure, flank masses, and urinary ascites.

•Older children with VUR and UTI may present with:

–Nonspecific signs and symptoms

–Urgency

–Frequency

–Dysuria

–Abdominal pain

–Incontinence

–Unless the UTI is associated with a fever, there is little reason to suspect VUR.

–Sometimes an enlarged urinary bladder may be palpable (Fig. 8.39).

–A palpable kidney is sometimes seen in those with associated hydronephrosis. Usually the affected kidney is not palpable

and small in size as measured by ultrasound.

–Children occasionally present with advanced reflux nephropathy, manifesting as headaches or congestive heart failure from untreated hypertension, or with uremic symptoms from renal failure.

–A small group of children without evidence of UTI present with symptoms of sterile reflux, which can include flank or abdominal pain before or during voiding, as well as double voiding or incomplete emptying resulting from delayed drainage of urine out of the upper tracts.