Enlargement of kidneys in fetus is detected on ultrasound examination during the first trimester. By 10th to 14th week of pregnancy, the kidneys of fetus start to function and baby releases urine into the amniotic fluid. The shape of kidney is similar to the shape of beans. It filters waste from the blood in the form of urine.
Kidney enlargement can occur in fetus, the condition is also called hydronephrosis. This condition is present in 1 percent of fetuses and both the genders are equally affected. Enlargement occurs due to blockage of urine due to defect in the urinary tract during its development.
In majority of cases enlarged kidneys does not pose any risk to the fetus or his development during pregnancy. However, this anomaly needs ultrasound monitoring from time to time throughout pregnancy period. Small percentage of children requires surgical correction after birth.
Causes Of Enlarged Kidneys In Fetus
There are many causes of enlargement of kidney in fetus during pregnancy. Below are some of the common observed causes.
- One of the most common causes relates to physiological dilatation of the renal pelvis. The pelvic structure of both the kidneys is dilated.
- Blockage of ureter at the junction of kidney or at the junction of bladder. Ureter is a tube that connects kidney with the bladder. Blockage or obstruction at junction of any of this organ can cause build up of urine in the kidney. Excess collection of urine in the kidney will naturally make the kidney to enlarge to accommodate the fluid.
- Obstruction in urethra, especially in males can cause build up of urine in the bladder and kidney leading to dilatation of kidney.
- Vesicoureteral reflux is possible when the valve at the junction of ureter and bladder is weak. This results in back flow of urine in the kidney causing hydronephrosis.
- Tumors and cyst in one kidney can cause dilatation in other kidney. The other kidney has to compensate the function of the first damaged kidney.
Treatment Options For Enlarged Kidney In Fetus
Hydronephrosis in fetus is detected on ultrasonography that is done as a routine during pregnancy. Enlargement of kidney in fetus during this period usually does not need any treatment. However, the fetus and the kidney have to be monitored frequently through sonogram.
In some cases the amniotic fluid may be less. This may be due to leakage of urine or reduced production of urine. Reduced production of urine may indicate significant damage to the kidney. In majority of cases this may not happen, but intense monitoring and evaluation of the pediatrician and gynecologist may be necessary.
Sometimes pediatric nephrologist’s opinion may be necessary if treatment is required. In rare instances if the blockage is severe a tube may be passed to bypass the blockage in a pregnant woman. In some cases the doctor may suggest early delivery of the fetus. But in most cases no treatment is necessary for enlarged kidney in fetus present in womb.
Soon after birth the infant may need to be examined by the pediatric nephrologist. He may examine the child to find if the defect is still present and whether there is any need for surgical correction.