Introduction
The definition and understanding of mega cystitis may vary. It is usually seen in an ultrasound scan. However, the chance that the condition is diagnosed is 0.06 percent. It is more common in males than in females. A normal fetal bladder in ultrasound is observed as a circular or oval region in the pelvic region of the fetus that is echo-free. An echo-free region in an ultrasound image denotes an area where ultrasound is transmitted. Boy fluids like ascites, bile, etc., are sonolucent and appear as black echo-free areas in an ultrasound. On the other hand, areas that transmit and reflect sound waves appear gray to white in an ultrasound image.
What Is Megacystis?
An abnormally sizable urinary bladder that is revealed in ultrasound is referred to as fetal megacystitis. The condition is seen during antenatal and occurs in one in one thousand five hundred pregnancies. The condition is more frequent in boys than in girls. It is diagnosed during the first-trimester scan within the eleventh to the fifteenth week of pregnancy. If the diameter of the bladder is more than 7 mm longitudinally, it is called mega cystitis. The fetal kidneys produce urine ring its life in vitro. This is passed to the bladder through the ureter. The urine is stored in the urinary bladder until excreted through another tube called the urethra.
What Are the Causes of Megacystis?
The causes of Mega cystitis are divided into obstructive causes and non-obstructive causes. Obstructive causes include conditions that block the urethra. They can include the following:
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Urethral valves that are located posteriorly.
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Malformations in the urethra like stenosis (narrowing of the urethra), atresia (absence of an opening), and persistent cloaca (a developmental anomaly where the rectum, vagina, and the urinary tract open into a common opening).
The non-obstructive causes include:
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Prune belly syndrome (a rare condition characterized by weak abdominal muscles).
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Megacystis-microcolon-intestinal-hypoperistalsis syndrome (MMIHS, a rare condition where the muscles of the bladder and the intestines are affected).
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Vesicoureteral regurgitation (a condition where urine flows back to the ureter or the kidney).
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Neurogenic causes like stroke, brain tumor, spinal lesions, etc.
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Genetic disorders like megacystis microcolon intestinal hypoperistalsis syndrome (a rare condition where the muscles of the bladder and the intestines are affected).
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Chromosomal abnormalities (mainly trisomy 13 and trisomy 18)
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Primary giant urethra (a condition where the urethra is very big).
Generally, when mega cystitis is seen in an ultrasound, it is considered to be due to an obstruction or constriction in the urethra, which prevents the urine from flowing out of the bladder. Just over half of the cases had this as the root cause. This gradually can lead to a condition called oligohydramnios, which is a condition where there is too little amniotic fluid. As the urine gets stored in the bladder, it can adversely affect the kidneys and the ureter. The amniotic fluid (a fluid in the womb that acts as a cushion for the fetus and provides its nutrients) is mainly formed from fetal urine. The developing fetus draws the amniotic fluid into the lungs to help them develop. Further, the cushioning effect of the amniotic fluid aids in the proper development of the muscles and bones of the fetus.
When there is a total obstruction, the urine remains in the fetal bladder and is not released into the amniotic fluid. This causes the bladder to increase in size and decrease the amniotic fluid levels. As a result, the maturation of the lungs is hindered and becomes underdeveloped. This leads to a life-threatening condition called pulmonary hypoplasia. In addition, there is an increased risk of chromosomal abnormalities or genetic disorders. The level of obstruction, other underlying causes, and other findings determine the prognosis of the condition.
What Are the Additional Investigations Required?
If the healthcare provider suspects any chromosomal abnormality or genetic disorder, they may advise further genetic testing and counseling. Samples from the placenta (placenta biopsy or CVS-chorionic villus sampling) in the first trimester or a little of the amniotic fluid in the second trimester (amniocentesis) will be advised. This is to get a sample of fetal cells or cells that resemble fetal cells to check for chromosomal abnormalities and genetic disorders. The condition can be detected in the early stages of pregnancy. It will either resolve spontaneously or progress during the pregnancy. A series of ultrasounds will be done during pregnancy to monitor the growth of the fetus and to check for any abnormalities. If any other tests are required, the healthcare provider will deal with them accordingly.
What Is the Treatment for Megacystitis?
The treatment of the condition will vary, depending upon the underlying cause. If the fetus has no chromosomal abnormality, the condition (where the longitudinal diameter is 7 to 15 mm) will spontaneously resolve in ninety percent of cases. However, suppose the longitudinal diameter is more than 15 mm. In that case, it has a lower prognosis, as it stands a high risk of progressive obstructive uropathy (a condition where urine can not be drained into the urinary tract). The underlying pathology will determine the management of the condition. In addition, if the obstruction is severe, it can cause pulmonary hypoplasia, leading to perinatal death (death of the fetus).
How Is the Condition Managed After Birth?
The pediatrician, nephrologist, and urologist will work together after the baby is born to plan the possible treatments. After thoroughly evaluating the condition, they will advise the parents on the long-term and short-term effects and what to expect. The level of obstruction will determine the type of treatment. Most children with significant obstruction are more susceptible to kidney infections and kidney failure. Some may require a kidney transplant in the long run. Long-term respiratory symptoms, bladder dysfunction, poor growth, and musculoskeletal problems can be seen in these children.
Conclusion
A condition where the fetal urinary bladder appears to be enlarged is termed mega cystitis. It can have obstructive and non-obstructive causes. Management of the condition depends on the underlying cause. If the enlargement is less than 15 mm, it usually resolves spontaneously in most cases. Others might require constant monitoring.
