What is the normal urinary tract?
The urinary tract consists of the kidneys, ureters, bladder and urethra. The kidneys are the organs that are responsible for filtering waste products from the bloodstream and produce urine continuously. The urine drains down tubes called ureters from the kidneys to the bladder, which normally stores urine and empties intermittently by muscular contraction. The urine exits the bladder through the urethra in a process is called voiding or urination.
When the ureter enters the bladder it travels through the wall for a distance creating a tunnel so that a flap valve is created. This valve prevents urine that is in the bladder from backing up and returning into the ureter. Thus, when the bladder fills and later when it squeezes down to empty, back-up (that is, reflux of urine) is prevented because the valve operates in the same way as when you pinch off a soda straw. This valve-like action is important for several reasons:
- prevents bacteria (that often get into the urine) from getting to the kidneys
- protects the ureters and kidneys from high pressures generated by the bladder during urination
- permits removal of all of the stored urine with a single act of urination, because the bladder urine has nowhere to go other than out the urethra
Diagram of normal urinary tract
Diagram of ureter tunneling
What is vesicoureteral reflux?
With normal urination, the bladder contracts and urine leaves the body through the urethra. With vesicoureteral reflux, some urine goes back up into the ureters and possibly up to the kidneys. Reflux exposes the kidneys to infection. In children, particularly those in the first 6 years of life, urinary infection can cause kidney damage. The injury to the kidney may result in renal scarring and loss of future growth potential or widespread scarring and atrophy. Even a small area of scarring in one kidney may be a cause of high blood pressure later in life. Untreated reflux on both sides can, in the most severe instances, result in kidney failure requiring dialysis or kidney transplantation.
Why does vesicoureteral reflux occur?
The valve system at the ureterovesical (ureter-bladder) junction may be abnormal:
- In some children the tunnel of the lower ureter through the muscular wall of the bladder may not be long enough. For these children, there is a good chance that growth may provide the necessary difference to allow the valve to work.
- The ureter may enter into the bladder abnormally (usually too much to the side), resulting in a short tunnel. This reflux is less likely to resolve with growth.
|The ureter is shown tunneling through the bladder wall. |
1-if the tunneling of the ureter ends here, reflux is likely.
2-if the tunneling of the ureter ends here, reflux is possible.
3-if the tunneling of the ureter ends here, reflux is unlikely.
Some children have reflux because of underlying problems such as lower urinary obstruction (such as urethral valves), abnormal bladder behavior (such as uninhibited bladder contractions or hyperreflexic bladders), infrequent voiding, or constipation.
How is reflux evaluated?
Children who are suspected of having reflux should have a renal ultrasound and a voiding cystourethrogram (VCUG). Based on these studies, reflux can be classified into five grades - grade 1 is the least and grade 5 is the worst. Mild degrees of reflux have a good chance of resolving spontaneously with age. Chances of resolution with high-grade reflux (grade 4-5, or reflux related to an anatomic problem such as a long-standing obstruction) are much lower...> ..> ..>..>
|Normal kidney, ureter, and bladder||Grade I Vesicoureteral Reflux:|
urine (shown in blue) refluxes part-way up the ureter
|Grade II Vesicoureteral Reflux:|
urine refluxes all the way up the ureter
|Grade III Vesicoureteral Reflux:|
urine refluxes all the way up the ureter with dilatation of the ureter and calyces (part of the kidney where urine collects)
|Grade IV Vesicoureteral Reflux:|
urine refluxes all the way up the ureter with marked dilatation of the ureter and calyces
|Grade V Vesicoureteral Reflux:|
massive reflux of urine up the ureter with marked tortuosity and dilatation of the ureter and calyces
How is reflux treated?
Since many children will outgrow their reflux, they can be followed carefully, with their reflux monitored at intervals by tests such as VCUG, renal ultrasound, or nuclear voiding cystogram. During this follow-up period they are kept on a prophylactic (low-dose) antibiotic to keep the urine free of infection. Any fever or urinary tract symptoms (such as burning, frequency, urgency, straining, foul odor, bloody urine, or unusual incontinence) must be evaluated with urine analysis and urine culture. Children who develop breakthrough urinary infections in spite of prophylaxis are at risk for kidney damage and need to be considered for surgical correction of reflux.
How is reflux treated surgically?
Correction of reflux (ureteral reimplantation or ureteroneocystostorny) is recommended for high grades of reflux, for reflux that fails to resolve, or for patients with breakthrough infections. The traditional surgical approach involves opening the bladder and creating a new longer tunnel for the ureter through the bladder wall.
What about long-term follow-up?
Children with a history of reflux should probably be monitored life-long with measurement of height and weight, blood pressure, and urine analysis. Occasional ultrasound tests will assure that kidney growth is on target for age and size. If kidney function from previous reflux should deteriorate, the pediatric nephrology team can begin appropriate medication and dietary restriction.
What about other family members?
If one child in a family has reflux, there is a 1 in 3 chance of having an affected sister or brother. Because we know that the chances of kidney damage are highest in the first 6 years of life, we think that brothers and sisters in that age range should be studied (with examination, ultrasound and voiding study) even though they may not have been known to have urinary infections. ..msnavigation-->