What Are the Causes of Kidney Dilation in a Fetus?

Fetal kidney dilation is the anomaly most commonly detected through routine ultrasounds, according to Cornell University's Department of Urology. Further, doctors at Cornell explain that the condition is called prenatal hydronephrosis, and means that there may be a problem with urine flow. It is important to remember that up to half of the fetuses that have prenatal hydronephrosis no longer have the condition on the postnatal ultrasound.

Obstruction

• The most common reason for fetal kidney dilation is an obstruction of some type. Doctors at Wayne State University's Department of Urology explain that it "is not uncommon to see dilation of the kidney drainage system of a fetus before birth" and that most blockages are found at the beginning of the tube that connects the kidney and bladder. Obstructions vary in severity and are treated accordingly. Mild blockages are generally left alone and observed only.

Posterior Urethral Valves

• If there is no blockage present to explain fetal kidney dilation, another possible cause may be posterior urethral valves. According to Urology Web, the valves are congenital membranes that cause an obstruction. The membranes can cause a large range of symptoms, from mild voiding problems to renal failure in an infant. Serum studies and renal studies are conducted to determine the severity of the condition.

Prune Belly Syndrome

• Prune Belly syndrome, a congenital condition that involves deformities of the urinary tract, is the least likely cause of fetal kidney dilation, occurring in fewer than 1 percent of all cases, according to Cornell University. Prune belly syndrome, also named Eagle-Barrett syndrome, is discovered in about one out of 40,000 births, with 95 percent of the cases being male, according to Prune Belly Syndrome Network. The prognosis for a child diagnosed with prune belly syndrome is determined by the degree of dilation in the urinary tract.