Introduction
An obstruction of the bladder outlet may be the cause of pain a person experiences pain in the abdominal region, pain when urinating, or difficulty emptying the urine. When there is an obstruction, urine is prevented from entering the urethra (urine tube) at the bladder's neck. Approximately 1 in 4,000 live births result in bladder outlet obstruction, which is more prevalent in boys than in females. The illness is often referred to as obstructive uropathy or lower urinary tract obstruction (LUTO).
What Is Fetal Bladder Outlet Obstruction?
Understanding how the urinary tract (drainage for removing urine) functions helps to know more about bladder outlet obstruction. To put it simply, the kidneys (which we normally have two) filter blood and eliminate waste materials, which the body excretes in urine. The ureter, a tube that empties into the bladder, receives the urine that has accumulated in the pelvis. The urethra is a tube that normally drains urine from the bladder and out of the body. An obstruction of this normal process occurs in fetal bladder outlet obstruction.
The placenta (an important structure during pregnancy) primarily takes care of the unborn child throughout pregnancy. Urine is produced by the baby's kidneys starting as early as the fifth week of life. The volume of amniotic fluid (the fluid that covers the baby) covering the infant increases prior to birth as a result of the baby's kidneys producing urine. The fluid provides the infant with a cushion and room to move, and it is essential for the growth and maturation of the lungs.
Urinary tract problems account for twenty to thirty percent of birth defects that are detected before delivery. 40 percent of these infants will be born with hydronephrosis (kidney swelling).
When urine accumulates in this region of the kidneys, the pelvis enlarges or swells. When the enlargement measures more than 10 millimeters during 20 to 24 weeks of pregnancy, the condition is referred to as hydronephrosis.
What Causes Fetal Bladder Outlet Obstruction?
The most common reason why urine flow gets blocked is posterior urethral valves (PUV), a condition that only affects men. In this, the tiny tissue leaflets known as urethral valves are ill-positioned and have a narrow, slit-like aperture that might restrict the flow of urine entirely or partially. Urine may flow in the other direction because it cannot escape. Urine reflux (when urine runs backward) can affect all of the urinary tract organs, particularly the urinary tract, bladder, and kidneys.
Urine fills the urinary tract's organs, causing them to enlarge and become damaged. The degree of occlusion can vary substantially. The severity of the urinary tract issues will depend on the level of blockage. About one in every 8,000 to 25,000 live births result in PUV. According to certain research, PUV affects 10 % of fetuses with hydronephrosis. Urethral atresia, or a blocked or missing urethra, is the main cause of bladder outlet obstruction in female fetuses.
What Effect Does a Blocked Bladder Outlet Have on the Fetus?
Urine leaves the body through an opening, the urethra, after leaving the bladder. The posterior urethral valves (the incorrectly positioned valves at the urethral opening) are the most prevalent cause of bladder outlet obstruction. Urethral atresia, or a clogged or missing urethra, is the most common cause in females. The severity of bladder outlet blockage varies widely. A normal amniotic fluid volume and functioning kidneys are at one end of the spectrum. On the other end of the spectrum, babies can have issues with their kidneys, lungs, and other organs, as well as no amniotic fluid and a very swollen bladder.
The severity of the symptoms and the stage of pregnancy at which the difficulties occur will determine the issues the unborn child faces. The baby's prognosis usually worsens the worse the symptoms are and the earlier they are noticed. To monitor the urinary tract's appearance and determine if the condition is improving or growing worse, ultrasound tests are crucial. The issue may resolve itself in some situations. In other situations, the issue will worsen. What happens as the pregnancy proceeds will determine the course of treatment during the pregnancy, the prognosis, and the postpartum care plan for the infant.
How Is Fetal Bladder Outlet Obstruction Correction Done During Pregnancy?
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Fetal Shunting - It is the most commonly used fetal intervention. This involves placing a small, flexible tube, or shunt, into the bladder of the fetus. The tube is designed so that one end remains in the bladder and the other end enters the amniotic sac. Urine can pass through the obstruction and exit the fetal bladder through shunting. To allow the lungs to develop, this causes the amniotic sac to fill with more fluid. Although the surgery may reduce tension in the kidneys and bladder, renal function cannot be restored.
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Vesicocentesis - In this, a needle is inserted into the bladder to extract the urine from the fetal bladder. The process might be carried out one time or multiple times.
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Fetoscopic Cystoscopy - To clear the blockage and restore urine flow, a tiny surgical camera is placed into the fetal urethra and bladder.
How Is a Bladder Outlet Obstruction Managed?
If obstruction of the bladder outlet is suspected, a thorough ultrasound examination should be performed to check for additional birth abnormalities. The symptoms of obstruction of the bladder outflow are varied. In moderate cases, the volume of amniotic fluid remains within the usual range, the kidneys do not exhibit any aberrant changes, and the bladder and ureters show minor modifications. In severe cases, the kidneys exhibit aberrant alterations, the bladder and ureters expand excessively, and there is an insufficiency of amniotic fluid (oligohydramnios). Treatment both before and after birth will differ due to this broad range of severity.
In less severe situations, the infants will require follow-up care shortly after birth from a urologist (a specialist in treating abnormalities of the urinary system) or nephrologist (a specialist in treating problems of the kidneys). In severe cases, the absence of amniotic fluid preventing lung development and kidney impairment may make intensive treatment difficult. Because of the extensive organ damage, palliative care may be the best course of action for these babies.
Conclusion
Urine flow obstruction along the urethra, the tube that empties the bladder and exits the body, is known as fetal bladder outlet obstruction. In mild situations, the best possible outcome is seen when the concentration of fluid around the infant is normal, and the baby's kidneys are operating. In extreme circumstances, certain fetal procedures are carried out. Women undergoing fetal surgery for bladder outlet obstruction need to be constantly monitored until their baby is born.
