Vesicoureteral Reflux (VUR)

Orientation

The big picture

Normally the ureterovesical junction is a one-way valve: urine enters the bladder but cannot flow back up the ureter, even when bladder pressure spikes during voiding. This protects the kidney from both high pressure and infected bladder urine. When the valve fails, urine refluxes upward — and the danger is not the reflux itself but what it carries: infected, high-pressure urine reaching the kidney causes pyelonephritis and renal scarring. That is why VUR matters and why it is chiefly a disease of protecting children's kidneys.

Golden rule

The framework: understand the valve mechanism (the oblique submucosal tunnel), divide reflux into primary (a congenital valve deficiency) and secondary (driven by something else, like high bladder pressure), grade it I–V, and treat — mostly conservatively, surgery when needed.

Pathophysiology

Mechanism pathway

Tap any step to see why it happens.

Illustration

Vesicoureteral reflux — grades I–V

Vesicoureteral reflux — grades I to V

Watch two things across the panels: how high the refluxed urine climbs (blue), and what happens to the calyces — the sharp, cupped fornices of a normal calyx (Grade II) progressively blunt (III), flatten / club (IV), then balloon as the ureter grows dilated and tortuous (V).

Renal parenchyma Refluxed urine (collecting system / ureter) Bladder

Grade I

Ureter only

Reflux reaches the distal ureter only. Pelvis and calyces are not filled. No dilation.

Grade II

Up to calyces · sharp

Fills ureter, pelvis & calyces, but everything stays normal calibre; calyces keep their sharp cups.

Grade III

Mild dilation · blunting

Pelvis begins to dilate and the ureter mildly widens; calyces are mildly blunted (cups flattening).

Grade IV

Moderate · clubbed

Moderate dilation of pelvis & ureter; calyces fully blunted / clubbed (rounded, fornices lost).

Grade V

Gross · tortuous

Gross dilation with a tortuous, wide ureter and severely ballooned calyces.

The grade is read from a voiding cystourethrogram (VCUG) and tells you two things at a glance — how high the urine refluxes and how dilated/deformed the collecting system is: I ureter only · II up to the calyces but undilated, calyces still sharp · III mild pelvic/ureteric dilation, calyces mildly blunted · IV moderate dilation, calyces clubbed · V gross dilation with a tortuous ureter and ballooned calyces. The sharper the calyces and the less the dilation, the lower the grade — and the higher the chance of spontaneous resolution with a lower risk of renal scarring. Grounded in leading urology references (International Reflux Study grading).

Work-up

Diagnostic algorithm

Each step answers one question. Tap to expand.

Exam

Board traps

The danger is infected, high-pressure urine reaching the kidney → scarring, not reflux per se.

Valve competence = tunnel length ÷ ureter diameter; reimplant aims for a 3–5× tunnel.

Primary = congenital trigonal muscle deficiency; secondary = driven by high pressure/dysfunction (treat the cause).

A negative VCUG doesn't exclude reflux — repeat the voiding cycle; intermittent reflux occurs with infection.

Conservative care + prophylaxis is first-line; surgery for breakthrough infection, non-resolving high grade, or scarring.

Constipation/bladder dysfunction worsens reflux — manage it.

Test yourself

Quiz

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