Posterior urethral valve (PUV) refers to a defect of the urethra, which is the tube that transports urine from the bladder to the genitals so that urine can pass out of the body. PUV occurs when the urethral valves—consisting of small sheets of tissue—have a constricted, slit-like opening that partially obstructs urine flow. As a result, the fluid reverses its flow and causes the organs along the urinary tract (including the ureters, bladder, urethra, and kidneys) to become engorged and swollen. This can lead to cell and tissue damage. The amount of obstruction caused by this urologic condition will determine the severity of the urinary tract problems.
Cause of PUV
A fetus' urethra develops while in the womb. Inside of the urethra tube is tissue; it too grows. At some point in normal development, however, the tube and its tissue stop forming. With posterior urethral valve, the tissue continues to grow, forming a flap which restricts the release of urine. The exact reason why the tissue continues building is unknown, but genetics may be involved, as has been noted in cases involving twins and siblings. Posterior urethral valve (PUV), which affects one in 8,000 male infants, may also occur by chance.
Symptoms of PUV
Posterior urethral valve is the most common contributor of urinary tract obstruction in children. The disorder may strike with varying degrees, from mild to severe. Every child with PUV may experience symptoms in different ways, but the following are the most common symptoms of PUV:
- An enlarged bladder that may appear through the abdomen as a huge mass
- Painful urination
- Weak urine stream
- Frequent urination (or overactive bladder)
- Bed-wetting or wetting pants following successful toilet-training
- Poor weight gain
- Difficulty with urination
- Enlarged kidneys
- Hydronephrosis (distention and dilation of the kidney as a result of urine build up)
- Underdeveloped lungs as a result of decreased amniotic fluid
- Vesicoureteral reflux (urine reverses its flow from the bladder to the upper urinary tract)
In addition to the above symptoms, fever, vomiting, loss of appetite, and irritability may occur.
When pregnant, a fetal ultrasound is performed to monitor the health of the fetus. This imaging test often makes a soft diagnosis of posterior urethral valve, which is most commonly characterized by a dilated bladder and kidneys. An ultrasound, which uses sound waves to create images of the body's organs, doesn't necessarily verify the condition; rather, it reveals the amount of swelling of the kidneys as well as the bladder's shape.
Should the diagnosis not be made in utero, many children are later diagnosed after they have developed a severe urinary tract infection and require medical attention. This may then prompt diagnostic tests, such as:
- Blood test - A blood sample may be taken from the child in order to evaluate his electrolytes and kidney function.
- Abdominal ultrasound - High-frequency sound waves and a computer generate visuals of the child's tissues, organs, and blood vessels. Enlarged kidneys, a dilated bladder, and other physical symptoms associated with PUV can be detected.
- Voiding cystourethrogram (VCUG) - A catheter tube is inserted into the urethra and advanced up to the bladder, which is then filled with contrast dye. X-rays are then taken to see how the dye moves through the urinary tract. If the dye reverts back to the kidneys, the child has vesicoureteral reflux, a symptom of PUV. Additional images are taken as urine passes through the urethra to see if a blockage is present.
- Endoscopy - A small, bendable tube with a light and camera at its tip (endoscope) is inserted into the urethra and guided up the urinary tract. The visual provided by the scope can detect an overgrowth of urethral tissue, which may be extracted for examination and testing (biopsy).
Treatment for PUV
Relieving pressure on the urinary tract and restoring fluids are the first steps when considering PUV treatment options. Once these areas are managed, and depending on the severity of the condition, surgery may be performed. This can include an endoscopic valve ablation, a pyleostomy, or a vesicotomy.
RA Kukreja, RM Desai, RB Sabnis, et al. (2001). Outcome of children with posterior urethral valves: Prognostic factors. Indian Journal of Urology. Vol. 17.
Urine blockage in newborns. (2010). National Kidney and Urologic Diseases Information Clearinghouse. NIH Publication No. 06-5630
Comprehensive Neonatal Care: An interdisciplinary approach. (2007). Saunders Elsevier.