Posterior urethral valves (or PUV) are an abnormality of the urethra, which is the tube that drains urine from the bladder to the outside of the body for elimination. The abnormality occurs when the urethral valves, which are small leaflets of tissue, have a narrow, slit-like opening that partially impedes urine outflow. Reverse flow occurs and can affect all of the urinary tract organs including the urethra, bladder, ureters, and kidneys. The organs of the urinary tract become engorged with urine and swell, causing tissue and cell damage. The degree of urinary outflow obstruction will determine the severity of the urinary tract problems.
What causes posterior urethral valves?
PUV are the most common cause of severe types of urinary tract obstruction in children. It is thought to develop in the early stages of fetal development. The abnormality affects only male infants and occurs in about one in 8,000 births. This disorder is usually sporadic (occurs by chance). However, some cases have been seen in twins and siblings, suggesting a genetic component.
What are the symptoms of posterior urethral valves?
The syndrome may occur in varying degrees from mild to severe. The following are the most common symptoms of posterior urethral valves. However, each child may experience symptoms differently which includes:
- an enlarged bladder that may be detectable through the abdomen as a large mass
- urinary tract infection, or UTI (usually uncommon in children younger than 5 years and unlikely in boys at any age, unless an obstruction is present)
- painful urination
- weak urine stream
- urinary frequency
- bedwetting or wetting pants after the child has been toilet-trained
- poor weight gain
- difficulty with urination
The symptoms of PUV may resemble other conditions or medical problems. Always consult your child’s physician for a diagnosis.
How are posterior urethral valves diagnosed?
The severity of the obstruction often determines how a diagnosis is made. Often, PUV are diagnosed by fetal ultrasound while a woman is still pregnant. Children who are diagnosed later often have developed urinary tract infections that require evaluation by a physician. This may prompt your physician to perform further diagnostic tests, which may include:
- Abdominal ultrasound: a diagnostic imaging technique that uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels.
- Voiding cystourethrogram (VCUG): a specific x-ray that examines the urinary tract. A catheter (hollow tube) is placed in the urethra (tube that drains urine from the bladder to the outside of the body) and the bladder is filled with a liquid dye. X-ray images will be taken as the bladder fills and empties. The images will show if there is any reverse flow of urine into the ureters and kidneys.
- Endoscopy: a test that uses a small, flexible tube with a light and a camera lens at the end (endoscope) to examine the inside of part of the urinary tract. Tissue samples from inside the urinary tract may also be taken for examination and testing.
- Blood test: may be ordered to assess your child’s electrolytes and to determine kidney function.
Treatment is by endoscopic valve ablation. Fetal surgery is a high risk procedure reserved for cases with severe oligohydramnios, to try to limit the associated lung underdevelopment, or pulmonary hypoplasia that is seen at birth in these patients. The risks of fetal surgery are significant and include limb entrapment, abdominal injury, and fetal or maternal death. Specific procedures for in utero intervention include infusions of amniotic fluid, serial bladder aspiration, and creating a connection between the amniotic sac and the fetal bladder, or vesicoamniotic shunt.
There are three specific endoscopic treatments of posterior urethral valves:
- Vesicostomy followed by valve ablation – a stoma, or hole, is made in the urinary bladder, also known as high diversion, after which the valve is ablated and the stoma is closed.
- Pyelostomy followed by valve ablation – stoma is made in the pelvis of the kidney as a slightly lower high diversion, after which the valve is ablated and the stoma is closed
- Primary (transurethral) valve ablation – the valve is removed through the urethra without creation of a stoma
The standard treatment is primary (transurethral) ablation of the valves. Urinary diversion is used in selected cases, and its benefit is disputed. Following surgery, the follow-up in patients with posterior urethral valve syndrome is long term, and often requires a multidisciplinary effort between urologists, pulmonologists, neonatologists, radiologists and the family of the patient. Care must be taken to promote proper bladder compliance and renal function, as well as to monitor and treat the significant lung underdevelopment that can accompany the disorder.
- Urinary tract infection
- Renal failure
- Vesicoureteral reflux