Introduction:
The urinary system consists of organs that aid in producing and storing urine. Organs include a pair of kidneys, a pair of ureters, the urinary bladder, and the urethra. When the fetus grows inside the womb, the urine produced by the kidneys passes or flows through the ureters into the bladder area. Urine gets stored in the bladder till it becomes full. When the bladder becomes full, it pushes the urine from the body through the urethra. The upper urinary tract consists of kidneys and ureters; the lower urinary tract consists of the bladder and urethra.
What Is Fetal Lower Urinary Tract Obstruction (LUTO)?
Fetal lower urinary tract obstruction is a rare and serious condition in a developing fetus when a blockage occurs in the urinary system. It not only causes abnormal development in the urinary tract; but also causes underdevelopment of the lungs. Since the baby faces difficulty emptying the bladder, the bladder gets inflated and becomes very large with time.
When a lower urinary tract obstruction occurs, parts of the urinary tract lying above the obstruction swells up with urine that cannot be drained. With time, this blockage leads to permanent damage to the kidneys. When the urine is no longer drained, the amniotic fluid surrounding the fetus decreases, leading to lung damage since the fetus moves the amniotic fluid in and out of the lungs for them to develop properly. This way, LUTO causes damage to more than one organ system.
What Causes Fetal Lower Urinary Tract Obstruction?
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A fetal lower urinary tract obstruction can be caused by genetic disorders or certain problems with the fetus’s chromosomes.
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Additional organ abnormalities or medical problems will be present.
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Sometimes, in a male fetus, a tissue fold from the bladder called the posterior urethral valve will block the hole, which allows the bladder drainage to the urethra.
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The urethral parts can be too narrow or completely blocked in other cases.
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A fetal lower urinary tract obstruction without any specific underlying condition is called an isolated LUTO.
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Amniocentesis and ultrasounds will help determine the cause of a LUTO; however, tests after birth can give an accurate analysis of the fetus's condition.
How Is Fetal Lower Urinary Tract Obstruction Diagnosed?
The diagnosis of lower tract obstruction is made by ultrasound in the middle of the second trimester. The commonly done tests include:
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Ultrasound - A high-resolution level 2 ultrasound is a noninvasive imaging technique used to assess a fetus's overall growth and development, the condition of the kidneys, and the severity of the obstruction.
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Magnetic Resonance Imaging - An ultrafast MRI can evaluate the genitourinary tract in complex cases.
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Fetal Echocardiogram - This procedure evaluates the fetal heart and assesses its structure and function.
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Renal Function Profile - This procedure is done after a complete bladder drainage is performed three to four times at an interval of one or two days to evaluate the renal function and understand the improvement of the urine electrolytes below the established thresholds that indicate a potential to save the kidneys.
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Fetal Chromosome Studies - These studies can confirm the gender of the fetus, as female fetuses with this urinary anomaly do not benefit from a fetal intervention. Fetal chromosome studies can also rule out chromosomal abnormalities affecting a baby’s long-term outcome or survival.
By performing a thorough evaluation, it is possible to understand whether or not the baby benefits from a medical intervention. An enlarged bladder of the fetus with normal amounts of amniotic fluid volume shows an incomplete obstruction. Such cases will be followed by ultrasound till the levels of amniotic fluid decrease. During initial ultrasound evaluation, the presence of cysts in the kidneys of the fetus is an indication of irreversible kidney damage. In such cases, medical intervention will not improve outcomes and hence will not be performed.
How Is Fetal Lower Urinary Tract Obstruction Managed?
If the lower urinary tract obstruction is an isolated LUTO, surgical interventions will reduce the amount of kidney and lung damage that occurred during pregnancy. The goal of the treatment is to provide constant urine drainage from the body to the amniotic fluid. This prevents urine buildup and helps normalize the amniotic fluid volume. The treatment depends on the urinary tract blockage. The different types of treatment include:
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Vesicocentesis - In this procedure, a needle is placed into the fetus's bladder to remove urine. Multiple procedures may be required if the urine repeatedly builds in the bladder. To resolve LUTO, one among ten fetuses requires a single vesicocentesis.
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Vesicoamniotic Shunt - A small plastic tube called the shunt is inserted into the bladder to allow the urine to flow outside the fetus.
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Fetal Cystoscopy - In this procedure, a small surgical camera called the cystoscope can be inserted into the fetus’s bladder and urethra to remove any blockages of the urine flow.
Not all fetal treatments are successful. In some cases, the fetus's position makes it difficult for it to be recognized on ultrasound, making it difficult for the fetal therapy procedure. Complications can also occur even when the fetal treatment reduces the urine amount trapped inside the baby. Over time, the urine can also build up again.
What Happens to a Fetus After the Management of Lower Urinary Tract Obstruction?
A baby who has received treatment for a lower urinary tract obstruction has to be delivered to a hospital with a NICU (neonatal intensive care unit). After delivery of the child, several other testing should be done in the NICU to understand the cause of the LUTO. After understanding the diagnosis, surgical intervention to provide a permanent solution for the expulsion urine from the baby's body will be carried out. Other therapies such as kidney transplants and dialysis may also be needed. A baby's sickness after birth will depend on the severity of the kidney and lung damage and what caused the LUTO.
Conclusion:
Lower urinary tract obstruction occurs when the urine flow is blocked from being let out of the body at the level of the lower urinary tract. Depending on several factors, this condition can be diagnosed and is usually managed during pregnancy. Mild forms of this disease with functional defects lead to a minimal clinical sequence. The severe forms can cause oligohydramnios (low amniotic fluid levels during pregnancy), renal dysplasia (abnormal development of the baby's kidneys in the womb), and a distended urinary tract.
