What Are the Causes of Fetal Kidney Disease?

It is possible for the fetal urinary system to develop diseases while in the womb. Diseases that affect the kidneys and ureters (the tubes that carry urine from the kidney to the bladder) can affect the fetus or may not cause problems until after birth, and sometimes no symptoms arise until several decades later.

Significance

• According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), urine production begins about 10 to 12 weeks after conception. While the placenta takes care of filtering wastes for the developing kidneys, the urine flows into the amniotic sac and becomes an important part of the amniotic fluid. Any disease that affects the kidneys' ability to produce and release urine is a potential cause of problems for the fetus, affecting not only the kidneys but the ability of the lungs to develop properly because they need adequate amniotic fluid.

Hydronephrosis

• Hydronephrosis is caused by a defect in the urinary tract that blocks the flow of urine in the unborn baby. The blockage causes urine to back up, which causes swelling in the kidneys or ureters. (When the swelling is in the ureters it's called hydroureter.) Information published by Cornell University states that hydronephrosis is the most commonly detected fetal kidney disease, affecting about 1.4 percent of unborn babies. The urinary obstruction is usually caused by a kink in the tube that carries urine out of the kidney. Any build-up of urine can cause infections, scarring and long-term damage to the kidney.

Kidney Dysplasia

• In this fetal kidney disease, the structures inside the kidney do not develop normally. The tubule system that collects urine begins with one tube that branches out into smaller tubes, creating an extensive system. In kidney dysplasia, the tubes do not branch out properly so the urine doesn't have anywhere to go. The urine collects in the kidney and forms into cysts that replace the normal kidney tissue. Kidney dysplasia usually only affects one kidney, so the baby can develop normally using the remaining healthy kidney. If both kidneys are affected, the fetus usually does not survive, and if he does live he will need dialysis and a kidney transplant. Kidney dysplasia can be inherited or it can be caused by the mother's use of illegal drugs or prescription medication used to treat seizures and high blood pressure.

Polycystic Kidney Disease

• There are two types of inherited polycystic kidney disease (PKD): autosomal dominant and autosomal recessive. Both types cause fluid-filled cysts to form in both kidneys. The cysts replace the normal kidney tissue so the kidneys can't work properly, and eventually they permanently fail. The signs of autosomal recessive PKD usually begin before birth. Ultrasound may show enlarged kidneys and scarring in the liver even though the cysts are visible. Children born with infantile PKD develop kidney disease before adulthood, but in the worst case, babies can die hours after birth.

Medullary Sponge Kidney Disease

• This is a birth defect that causes tiny cysts to block the tubes in the kidneys so urine can't flow through them. This disease develops before the baby is born but usually doesn't cause any problems until about age 30 or 40, and then it manifests as urinary tract infections and kidney stones. The NIDDK reports that about 20 percent of adults with kidney stones have medullary sponge kidney disease (MSK). However, MSK seldom progresses to kidney failure.