Urinary Tract Obstruction in Children

What is a Urinary Tract Obstruction?

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.

How Does the Urinary Tract Function normally?

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.

Upper Tract Obstructions

1. UPJ obstruction - short, narrow segment of the upper ureter at. the junction with the renal pelvis above.
2. UVJ obstruction - narrow segment of the distal ureter just above its entry into the urinary bladder.
3. 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.

Lower Tract Obstructions

1. Meatal stenosis - acquired stricture of the urethral meatus at the tip of the penis.
2. Posterior urethral valves - valve leaflets that block the urine How out of the prostatic urethra.

Neurogenic Bladder

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?

1. Renal ultrasound (sonogram): uses sound waves to visualize kidneys and is particularly sensitive to dilation of the urinary collecting system.
2. 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 the study.
3. 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.
4. 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 the tube.
5. 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 sphincter relaxation.
6. 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 anatomy.

What problems are associated with Urinary Tract Obstructions?

Most urinary tract obstructions are discovered "accidentally" when 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.

How are Uriniary Tract Obstructions managed?

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.