Any blockage to the free flow of urine along
the urinary tract may produce a urinary tract
obstruction: This will result in the pooling
(stasis) of urine and may increase the pressure
within the urinary tract above the point of obstruction.
Eventually, kidney damage and urinary tract infections
become more likely to occur in obstructed situations.
Some conditions producing urinary tract obstruction
are present at birth and are considered congenital
causes. Others occur later on in life and are
acquired causes. However, it must be emphasized
that many congenital forms of urinary tract obstruction
only become clinically apparent and detectable
later on in life.
The kidneys act as a filter, removing waste
products from the blood stream, resulting in
the ton-nation of urine. The rest of the urinary
tract works like a sophisticated plumbing system
to allow the transport of urine out of the body.
The urinary tract pathway (urinary collecting
system) includes: the renal pelvis, ureters,
bladder and urethra. This system allows for the
free How of urine away from the kidneys, down
into the bladder for temporary storage, before
finally emptying out through the urethra. This
system is designed to maintain "low" pressure
within the urinary tract and avoid prolonged
pooling of urine.
- UPJ obstruction - short, narrow segment of
the upper ureter at. the junction with the
renal pelvis above.
- UVJ obstruction - narrow segment of the distal
ureter just above its entry into the urinary
- Ureterocele - abnormal balloon-like dilation
of the most distal end of the ureter usually
associated with the upper segment of a duplicated
collecting system to a single kidney.
- Meatal stenosis - acquired stricture of the
urethral meatus at the tip of the penis.
- Posterior urethral valves - valve leaflets
that block the urine How out of the prostatic
1) Neurogenic dysfunction of the lower urinary
tract may affect the ability of the bladder muscle
to contract to empty itself or appropriate coordination
of bladder contractions with relaxation of the
sphincter muscles for emptying.
What diagnostic studies are helpful in the accurate
evaluation of Urinary Tract Obstructions?
- Renal ultrasound (sonogram): uses sound waves
to visualize kidneys and is particularly sensitive
to dilation of the urinary collecting system.
- Diuretic Renal Scan: accurately estimates
each kidney's function and drainage capabilities;
an injection of radioisoiope contrast into
the child's vein is followed by a diuretic
(lasix) to encourage a large urine output during
- Intravenous Pyeigram (IVP): an injection
of iodine contrast into a vein is followed
by a series of x-ray films to demonstrate urinary
tract anatomy and provide limited information
on each kidney's function.
- Antegrade Pressure Pet-fusion Study (Whitaker
Test): a small tube is placed through the skin
into the kidney (nephrostomy tube) with the
measurement of the renal pelvic pressure in
response to a constant flow of fluid through
- Urodynamics: water or gas infused through
a small catheter passed into the bladder to
measure bladder pressure and estimate the coordination
between bladder muscle contractions with urethral
- Voiding Cystourethrogram (VCUG): iodine contrast
fluid fills the bladder through a small catheter
allowing x-ray films to be obtained during
the filling and voiding phases of the bladder;
this study demonstrates the lower urinary tract
Most urinary tract obstructions are discovered
the urinary tract is observed on ultrasound studies
during pregnancy. The infant usually does not
demonstrate any adverse sign of symptoms that
can be attributed to having an underlying obstruction.
Later on in life, the development of a wide spectrum
of problems may result from urinary tract obstruction.
These include: vague back or abdominal pains,
urinary tract infections, palpable abdominal
mass, inability to urinate, evidence of kidney
damage or even renal failure in children.
Corrective surgery is directed at the specific
site of obstruction within the urinary tract
to re-establish the free flow of urine through
the system. These procedures include: pyeloplasty
for UPJ obstruction, ureteral reimplantation
for UVJ obstruction and ureterocele, TUR-valves
for posterior urethrral valves, and meatotomy
for meatal stenosis. Neurogenic bladder problems
often require a combined approach which may include
clean intermittent catheterization, medication,
and surgery to improve bladder capacity. Most
importantly, in dilated urinary tracts that are
not clearly obstructed on the initial imaging
studies, corrective surgery should be withheld.
The urinary tract is a "live" plumbing system
that may develop satisfactorily in these situations
without surgical intervention. Follow-up imaging
studies are essential in following the growth
and development of the urinary tract in children.
Should there be definite evidence of kidney deterioration
on subsequent studies, surgical correction can
usually be accomplished successfully.
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Pediatric Urological Surgery
Should Know About