Classification

Reflux severity is graded using the International Reflux Study Classification of I to V and is based on the appearance of the urinary tract on a contrast voiding cystourethrogram (VCUG) (Figs. 533-2 and 533-3). The higher the reflux grade, the greater the likelihood of renal injury. Reflux severity is an indirect indication of the degree of abnormality of the ureterovesical junction.

Figure 533-2 Grading of vesicoureteral reflux. Grade I: reflux into a nondilated ureter. Grade II: reflux into the upper collecting system without dilatation. Grade III: reflux into dilated ureter and/or blunting of calyceal fornices. Grade IV: reflux into a grossly dilated ureter. Grade V: massive reflux, with significant ureteral dilatation and tortuosity and loss of the papillary impression.

Figure 533-3 Voiding cystourethrogram showing grade IV right vesicoureteral reflux.

Reflux may be primary or secondary (Table 533-1). Bladder and bowel dysfunction instability can worsen pre-existing reflux if there is a marginally competent ureterovesical junction. In the most severe cases, there is such massive reflux into the upper tracts that the bladder becomes overdistended. This condition, the megacystis-megaureter syndrome, occurs primarily in boys and may be unilateral or bilateral (Fig. 533-4). Reimplantation of the ureters into the bladder to correct reflux resolves the condition.

Table 533-1 CLASSIFICATION OF VESICOURETERAL REFLUX

Figure 533-4 Voiding cystourethrogram in newborn boy with megacystis-megaureter syndrome. Note the massive ureteral dilatation due to high-grade vesicoureteral reflux. The bladder is very distended. There was no urethral obstruction or neuropathic dysfunction.

Approximately 1/125 children have a duplication of the upper urinary tract in which 2 ureters rather than 1 drain the kidney. Duplication may be partial or complete. In partial duplication, the ureters join above the bladder and there is 1 ureteral orifice. In complete duplication, the attachment of the lower pole ureter to the bladder is superior and lateral to the upper pole ureter. The valve-like mechanism for the lower pole ureter often is marginal, and reflux into the lower ureter occurs in as many as 50% of cases. Reflux occurs into both the lower and upper systems in some persons (Fig. 533-5). With a duplication anomaly, some patients have an ectopic ureter, in which the upper pole ureter drains outside the bladder (Chapters 534 and 537 and see Figs. 537-6 and 537-7). If the ectopic ureter drains into the bladder neck, typically it is obstructed and refluxes. Duplication anomalies also are common in children with a ureterocele, which is a cystic swelling of the intramural portion of the distal ureter. These patients often have reflux into the associated lower pole ureter or the contralateral ureter. Generally reflux is present when the ureter enters a bladder diverticulum (Fig. 533-6).

Figure 533-5 Various anatomic defects of the ureterovesical junction associated with vesicoureteral reflux.

Figure 533-6 Reflux and bladder diverticulum. The voiding cystourethrogram demonstrates left vesicoureteral reflux and a paraureteral diverticulum.

Reflux is present at birth in 25% of children with neuropathic bladder, as occurs in myelomeningocele, sacral agenesis, and many cases of high imperforate anus. Reflux is seen in 50% of boys with posterior urethral valves. Reflux with increased intravesical pressure (as in detrusor-sphincter dyssynergia or bladder outlet obstruction) can result in renal injury, even in the absence of infection.

Primary reflux occurs in association with several congenital urinary tract abnormalities. Of children with a multicystic dysplastic kidney or renal agenesis (Chapter 531), 15% have reflux into the contralateral kidney, and 10-15% of children with a ureteropelvic junction obstruction have reflux into either the hydronephrotic kidney or the contralateral kidney.

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