The Normal Urinary Tract
The kidneys filter the blood and extract waste products from the blood to
make urine. Urine passes from the kidneys, down the ureters, and into
the bladder for storage prior to urination.
The ureter enters the
bladder wall at an angle 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
(reflux) is prevented because the valve operates in the same way as you might
step on a straw.
This valve-like action creates an important barrier that
helps keep the kidneys free of bacteria. Once urine has passed from the upper
urinary tract into the bladder, the normal valve not only makes certain that
urine does not re-enter the upper tracts but also that the high pressures
created at the moment of urination are not transmitted to the kidneys. Another
important feature of the competent valve (ureterovesical junction) is that it
permits you to remove all of the stored urine from the body with a single act of
urination - because the bladder urine has nowhere to go other than out the
The valve system at the ureterovesical junction may be abnormal for a few
reasons. In many patients the tunnel of the lower ureter through the muscular
wall of the bladder may not be long enough. A ratio of at least 4:1 of tunnel
length to ureteral diameter is necessary to assure competence of the valve (this
means that the part of the ureter traveling through the wall of the bladder
should be at least four times as long as it is wide). For some children, there
is a good chance that growth may provide the necessary difference to allow the
valve to work.
Another reason for reflux may be that the location of entry
into the bladder is abnormal (usually too much to the side). The result of this
bad location is a short tunnel. Resolution of reflux with growth is less likely
when the ureteral opening is in a very abnormal location (ectopia).
children have reflux because of underlying problems such as lower urinary
obstruction (such as urethral valves), abnormal bladder behavior, infrequent
voiding, or constipation.
Problems with Reflux
The main problem with reflux is that it exposes the kidneys to infection. In
children, particularly those in the first six years of life, urinary infection
can cause kidney damage. Injury to the kidney may result in a small area of
scarring, 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 transplantation.
Because reflux results in incomplete emptying of the urinary tract, infection
may be encouraged. Some patients are also susceptible to kidney stone formation
because of their reflux.
Evaluation of Reflux
Our baseline evaluation of vesicoureteral reflux consists of an upper tract
study and a lower tract study. For most children, upper tracts can be
adequately evaluated by ultrasound. Even though we call this "the upper tract
study" at Mott Children's Hospital, it also includes a careful look at ureters
and bladder (you can also get tested from home). The quality of ultrasound at Mott has become so consistently high
that intravenous pyelograms (IVP - involving intravenous injection and
conventional x-rays) are no longer routinely necessary. When, however, some
aspect of the ultrasound study is suspicious or when the clinical history
suggests further evaluation, we will go ahead and recommend an IVP.
evaluated by a voiding cystogram and this generally requires a catheter passed
into the bladder to fill it with an imaging substance. The catheters used are
very small (usually the same size used for newborn babies). Nonetheless, for a
"first-timer" this procedure is threatening and requires some preparation and
reassurance. We give the patient a short course of antibiotics to cover this
procedure if none are otherwise being taken. A contrast voiding
cystourethrogram (VCUG), will also image the entire urethra to rule out valves
or other problems. Minimal x-ray exposure is involved and the testicles are
protected in boys. A nuclear voiding cystogram does not offer urethral
visualization but involves almost negligible radiation. The bladder is
instilled with a tiny amount of radioactive material and the ureters and kidneys
are scanned with a special camera during filling and voiding. The radioactive
substance has a very short life and is passed directly out of the urinary tract
without absorption into the body. This test is more sensitive than the x-ray
VCUG although not quite as specific in showing the degree of reflux.
is classified into five grades -- grade I is the least and grade V is the most
Nonoperative Management of Reflux
When reflux is related to an underlying problem such as constipation, infrequent
voiding, abnormal bladder activity, or blockages such as strictures or valves,
the predisposing factor should be corrected and the reflux then re-evaluated.
Mild degrees of reflux have a good chance of being outgrown (resolution of
reflux) with age. In 4 out of 5 children with mild to moderate degrees of
reflux, resolution can be expected over the course of some years.
Unfortunately, there is no magic crystal ball that will tell us exactly when the
reflux will go away for a particular child -- although recent data suggests that
resolution should be expected within a few years. The chance of resolution of
high grade reflux related to an anatomic problem is much lower.
Most of our
refluxing children are given a chance to outgrow their reflux. It is essential
that they be protected from urinary infection during this time, and for this we
use low doses of prophylactic antibiotics. After a 1-2 year interval with
antibiotics, reflux is re-evaluated. At the same time we check the kidneys with
ultrasound to be certain they are growth properly.
No antibiotic is
risk-free and no antibiotic will destroy all bacteria. Nonetheless, Bactrim or
Septra (same drug, different companies) have proved the most effective
prophylactic agents with minimal side effects and these are usually our first
During the course of nonoperative management, any fever or urinary
tract symptoms (burning, frequency, urgency, straining, foul odor, blood urine,
or unusual incontinence) must be aggressively evaluated with urine analysis and
urine culture. A breakthrough urinary infection, in spite of prophylaxis, is a
dangerous situation indicating that we are unable to protect the kidneys with a
nonoperative course of management and that the next step would be surgical
correction of reflux.
Surgical Correction of Reflux
Correction of reflux (ureteral reimplantation = ureteroneocystostomy) is
recommended for high grades of reflux, for reflux that fails to resolve, or for
patients with breakthrough infections.
The traditional surgical approaches
have high degrees of success and usually involve opening the bladder and
creating a new longer tunnel for the ureter to pass through the bladder wall.
If the ureter is very wide it may need to be narrowed to make a successful flap
valve with at least a 4:1 ratio of tunnel length to ureter width. Complications
include bleeding and infection in the short run, urinary leakage and bladder
spasms in the intermediate time course, and obstruction or persistent reflux
later. The child is left on prophylactic antibiotics for several months until
postoperative studies prove that the reflux has been corrected.
Follow-Up of Refluxing/Reimplanted Patients
We think that all patients with a history of reflux should be monitored
life-long. This usually involves little more than periodic visits after reflux
has been outgrown with measurement of height and weight, blood pressure and
urine analysis. Kidney function can be crudely evaluated by blood tests
(creatinine and BUN) or more precisely checked by creatinine clearance or
glomerular filtration rate. Occasional ultrasound tests will assure that kidney
growth is on target for age and size. The corrected refluxer is similarly
followed after the initial postoperative studies.
By the time surgical
correction has been performed, some children have already had significant kidney
damage. This is apparent in the finding that close to 20% of patients who had
undergone surgical correction of reflux later developed high blood pressure. In
other patients, the kidney damage from reflux earlier in life may result in
kidneys that don't grow in size or function proportionately with the body and
thereby seem to deteriorate with age. When kidney deterioration has been
demonstrated, the Pediatric Nephrology Team must begin careful surveillance with
appropriate medication and dietary restriction.
If a child with reflux has a brother or sister there is a 1 in 3 chance that the
sibling will also have reflux which may already have caused kidney damage in the
absence of any clinical suggestion of urinary infections. 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 aggressively studied (with
ultrasound and voiding studies) even though they may not have been known to have
urinary infection. Older siblings, in the absence of symptoms, can be more
simply screened with urine analysis and ultrasound.
Intravesical Correction of Reflux
Reflux can also be corrected by injecting material directly into the bladder
through a cystoscope. This potentially will spare the patient a traditional
operation with incision and can be done on an outpatient basis. The materials
currently in use are Teflon and collagen. This approach to reflux correction is
still somewhat controversial. Teflon persists lifelong and may migrate to other
sites in the body, although it seems to be inert and harmless. This is not
approved by the FDA at this point. We have had some experimental success with
collagen, a biodegradable material, however there is no long-term data and the
success rate drawbacks and complications are not yet known.
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