Kidney Defects

In the fetus, kidneys first develop in the pelvis and then move up and rotate into their normal location in the upper abdomen. If the kidneys are in the wrong place (ectopic kidneys) or are not rotated properly (malrotation), the normal drainage of urine from the kidneys through the ureters Ureters The ureters are muscular tubes—about 16 inches (40 centimeters) long—that attach at their upper end to the kidneys and at their lower end to the bladder. (See also Overview of the Urinary Tract... read more (the tubes that transport urine from the kidneys to the bladder) to the bladder Bladder The bladder is an expandable, muscular sac. Urine accumulates in the bladder as it arrives from the ureters. The bladder gradually increases in size to accommodate an increasing volume of urine... read more (the expandable, muscular sac that holds urine) may be blocked.

Children who have blockage that causes frequent urinary tract infections or other problems may need surgery. However, many children do not have symptoms and thus may not need surgery.

A horseshoe kidney is the most common fused kidney defect. In horseshoe kidney, the fetus's two kidneys join together into a single, horseshoe-looking shape. Because they are joined together, the kidneys do not usually move up and rotate into their normal location and also may not develop properly. Because of these factors, a horseshoe kidney may not drain properly, increasing the risk of urinary tract infections, kidney stones, and kidney damage. However, over half of children with a horseshoe kidney never have any symptoms. Children who have a horseshoe kidney may also have other birth defects.

In some children, one or both of the kidneys may not develop at all (kidney agenesis). Children who are missing both kidneys cannot survive.

In children who are missing only one kidney, the remaining kidney usually develops normally and often becomes bigger than normal to compensate for the missing one. In such cases, the child is expected to have a normal life expectancy and does not need any treatment.

Sometimes a kidney does not form properly and may not function properly or at all (kidney dysplasia). When only one kidney functions properly, it may become bigger than normal to make up for the loss of function of the other kidney. Because all of the functions normally done by two kidneys can be carried out adequately by one healthy kidney, children who have only one functioning kidney often lead normal, healthy lives. However, if dysplasia is widespread and affects both kidneys, children may need treatment to replace the kidney function. That is, they will need a kidney transplant Kidney Transplantation Kidney transplantation is the removal of a healthy kidney from a living or recently deceased person and then its transfer into a person with end-stage kidney failure. (See also Overview of Transplantation... read more or dialysis Dialysis Dialysis is an artificial process for removing waste products and excess fluids from the body, a process that is needed when the kidneys are not functioning properly. There are a number of reasons... read more (a way to remove waste products and excess fluids from the body).

Polycystic kidney disease is a hereditary disorder in which many fluid-filled sacs (cysts) form in both kidneys. The kidneys grow larger but have less functioning tissue.

There are several forms of polycystic kidney disease. One form, autosomal dominant polycystic kidney disease Polycystic Kidney Disease (PKD) Polycystic kidney disease is a hereditary disorder in which many fluid-filled sacs (cysts) form in both kidneys. The kidneys grow larger but have less functioning tissue. Polycystic kidney disease... read more , usually does not appear until adulthood and usually causes mild symptoms.

Autosomal recessive polycystic kidney disease is the rare form of this disorder that begins during childhood. In this disorder, the cysts become very large and cause serious illness. A severely affected newborn may die shortly after birth because kidney failure can develop before birth, leading to poor development of the lungs. The liver is also affected, and a child with this disorder tends to develop portal hypertension Portal Hypertension Portal hypertension is abnormally high blood pressure in the portal vein (the large vein that brings blood from the intestine to the liver) and its branches. Cirrhosis (scarring that distorts... read more , or high pressure in the blood vessels that connect the intestine and the liver (portal system). Eventually, liver failure Liver Failure Liver failure is severe deterioration in liver function. Liver failure is caused by a disorder or substance that damages the liver. Most people have jaundice (yellow skin and eyes), feel tired... read more and chronic kidney disease Chronic Kidney Disease Chronic kidney disease is a slowly progressive (months to years) decline in the kidneys’ ability to filter metabolic waste products from the blood. Major causes are diabetes and high blood pressure... read more occur. Infants who survive the newborn period may need kidney (and sometimes liver) transplantation.

Multicystic dysplastic kidney (MCDK) is the most common cyst-causing malformation of the kidneys in children. In MCDK, the kidney does not develop normally and instead has multiple fluid-filled sacs (cysts) that grow inside the kidney and take over the normal kidney tissue. The kidney does not function at all.

MCDK typically affects only one kidney. If it affects both kidneys, the fetus dies. However, children who have only one affected kidney often have a good outlook, depending on what other abnormalities, if any, they have. Sometimes the unaffected kidney has other defects that can cause blockage of urine flow or reflux of urine.

MCDK is usually detected during routine prenatal ultrasonography, and most children have periodic ultrasounds after birth to determine whether the unaffected kidney is functioning properly. The affected kidney almost always shrinks and disappears. If the kidney does not go away, doctors sometimes remove it later in childhood. Because the unaffected kidney usually becomes bigger over time to compensate for the affected one, children usually have normal kidney function. If children have urinary blockage that causes frequent urinary tract infections or other problems in the functioning kidney, they may need surgery.