In the fetus, the kidney structure from 4 months of pregnancy resembles the structure of the kidney of the already born baby - there is a parenchyma in which future urine forms and a excretory system. The urinary excretion system consists of cups and pelvis, where the cups open. Further, urine enters the ureter and bladder of the fetus, which it empties several times a day.
Kidneys in the fetus begin to function from 16 weeks of pregnancy. And on the second screening ultrasound examination in 18-21 weeks of pregnancy, it is necessary to check whether there are both kidneys and whether there are congenital malformations of the kidneys, urinary tract and bladder.
What is hydronephrosis in a fetus?
During embryogenesis, any teratogenic factor can cause congenital anomalies of the kidney, but it is also a vice in which heredity plays a big role. And if there were various congenital diseases of the kidneys in the genus, then they should pay special attention to the structure of the fetus.
Hydronephrosis is an expansion of the kidney cups and pelvis with urine. If the fetus has an enlargement of pelvis from 5 to 8 mm in the period up to 20 weeks of pregnancy or from 5 to 10 mm after 20 weeks, this is not hydronephrosis, but most likely the fetus helps the mother's kidneys work, which may not cope with the load and in this case, the kidneys of the pregnant woman should be examined.
But if an ultrasound examination of up to 20 weeks is found to expand the pelvis more than 8 mm, and after 20 weeks - more than 10 mm, then this is hydronephrosis. Most often it is one-sided and depends on at what level the narrowing of the urinary tract occurred.
If hydronephrosis of the right kidney is detected in the fetus, then the constriction could occur at the level of the right pelvis inflow into the ureter, in any part of the right ureter or at the point of entry into the bladder. It is also possible for the ureter to depart from the kidney incorrectly or to contract with an additional vessel.
A hydronephrosis of the left kidney in the fetus occurs because of the same obstruction on the left.
Hydronephrosis is dangerous because with the expansion, it is possible to squeeze the parenchyma with urine until it is completely destroyed, after which the hydronephrosis grows no longer, but the kidney can not be saved. Therefore, treatment is often prompt: if hydronephrosis is small - after the birth of the child, and if necessary - and during pregnancy on the kidney of the fetus (a temporary outflow of urine, followed by post-partum plastic surgery) is necessary.