Post urethral valves

The condition affects one out of four thousand boys. The valves are membranes that look like sails in the urethra which is the tube through which the urine draines to the outside (where we pee from). Consequently, the valves block the passage of urine from the bladder to the outside. They are analogous to pinching a hose while water is running through it. Just like in the hose, the pressure on the inflow side is increased in the portion of the urethra close to the bladder. This pressure is transmitted to the bladder and the kidneys.

Since the valves develop early on during gestation, the kidneys may not develop normally. The newborn may have various degrees of kidney damage. Also, the bladder (a muscular organ) has to push the urine much harder to overcome the obstruction to flow. This is analogous to a body builder lifting progressively higher weights to bulk up. The same changes occur in the bladder which becomes more muscular leading to abnormal function. The latter can range from “strong” and high pressure voiding to poor emptying of the urine. These problems require various types of surgical intervention as the baby grows and develops.

Symptoms

The diagnosis of posterior urethral valves is most frequently made by virtue of routine prenatal fetal ultrasonography in the first or second trimester of gestation. Although the valves themselves are not visualized, the secondary changes in the bladder and kidneys are. These consist of dilation (kidneys) or abnormal distention (bladder). Occasionally, the obstruction is so severe that there is very little urine produced. As a result the amniotic fluid volume can be markedly reduced or even absent. Fortunately, this extreme scenario is not the most frequent. The best case scenario is one where the bladder and kidneys are normal or near normal in structure and function.

In newborn boys in whom the diagnosis has not been made by prenatal sonography, the symptoms can consist of urinary tract infections or an abdominal mass from the enlarged bladder. In older children, in addition difficulty in toilet training can be the first symptoms.

Causes

Posterior urethral valves occur only in boys. The causation is not well known but it is not genetic or related to the environment. It is best to view it as a random event of development of the urethra.

Diagnosis

When the prenatal ultrasound suggests the presence of posterior urethral valves, the diagnosis is made at birth with a special X-ray of the bladder and urethra called voiding cystourethrogram. A small soft catheter is gently inserted in the urethra and bladder. The bladder is filled with a safe special solution and the anatomy is visualized. Additional tests depend on the individual specific findings, which can vary widely.

Special attention is focused on images of the urethra to look for obstruction.

Treatment

The initial treatment consists of opening the valves with a tiny instrument and camera inserted into the urethra. This is called a cystoscopy. Additional surgical procedures may be required depending on the size of the newborn, the condition of the bladder and kidneys.

Subsequent treatment can include medications, surgical procedures or a combination. The patients are carefully monitored over the length of childhood. This intensive and proactive approach has been shown to decrease the risk of kidney damage. However, some children will progress over time and develop a degree of kidney failure. A few will require kidney transplantation and or dialysis.

Posterior urethral valves are not associated with other anomalies in the body such as heart or nervous system problems. The majority can participate in most childhood activities.

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