There are several different birth defects that affect the kidneys Kidneys The kidneys are bean-shaped organs that figure prominently in the urinary tract. Each is about 4 to 5 inches (12 centimeters) long and weighs about one third of a pound (150 grams). One lies... read more (the two organs that filter waste from the blood to make urine). These defects are not usually apparent at the doctor's examination and require tests to evaluate the urinary tract Evaluation of Kidney and Urinary Tract Disorders A doctor obtains a medical history by interviewing a person. The interview includes questions about a person's symptoms, past medical history (what disorders the person has had), drugs (prescribed... read more .
(See also Overview of Urinary Tract Birth Defects Overview of Kidney and Urinary Tract Birth Defects Birth defects are more common in the kidney and urinary system (urinary tract) than in any other system of the body. Defects can develop in the Kidneys—the two organs that filter waste from... read more .)
A Look Inside the Urinary Tract
Complications of birth defects of the kidneys
There are many types of birth defects of the kidneys Types of Kidney Defects There are several different birth defects that affect the kidneys (the two organs that filter waste from the blood to make urine). These defects are not usually apparent at the doctor's examination... read more . Many of these defects
Block or slow the flow of urine out of the kidneys
Blockage of urine flow can cause urine to become stagnant and result in urinary tract infections Urinary Tract Infection (UTI) in Children A urinary tract infection is a bacterial infection of the urinary bladder ( cystitis), the kidneys ( pyelonephritis), or both. Urinary tract infections are caused by bacteria. Infants and younger... read more (UTIs) or formation of kidney stones Stones in the Urinary Tract Stones (calculi) are hard masses that form in the urinary tract and may cause pain, bleeding, or an infection or block of the flow of urine. Tiny stones may cause no symptoms, but larger stones... read more . Blockage of urine flow also can raise the pressure inside the kidneys and damage them over time. Kidney damage can cause high blood pressure High Blood Pressure High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more and, rarely, kidney failure Overview of Kidney Failure This chapter includes a new section on COVID-19 and acute kidney injury (AKI). Kidney failure is the inability of the kidneys to adequately filter metabolic waste products from the blood. Kidney... read more .
Types of Kidney Defects
A number of birth defects may result in abnormal kidneys. Kidneys may be
In the wrong location (ectopic kidneys)
Rotated the wrong way (malrotation)
Joined together (horseshoe kidney or fused kidneys)
Containing fluid-filled sacs (cysts), such as in polycystic kidney disease and multicystic dysplastic kidney
Kidneys in the wrong location and position
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.
Horseshoe Kidney (Renal Fusion) (Congenital Aganglionic Megacolon) (https://www.youtube.com/watch?v=mdKt8kLGfVA) by Osmosis (https://open.osmosis.org/) is licensed under CC-BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/).
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.
Poorly functioning kidneys
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
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.
Polycystic Kidney Disease
In polycystic kidney disease, many cysts form in both kidneys. The cysts gradually enlarge, destroying some or most of the normal tissue in the kidneys.
Multicystic dysplastic kidney
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.
Diagnosis of Kidney Defects
Prenatal ultrasonography and tests before birth, and imaging tests and physical examinations after birth
Sometimes biopsy of the kidney
Sometimes genetic testing
Before birth, urinary tract defects are often discovered by doctors during routine prenatal ultrasonography Ultrasonography Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more or other routine screening tests for hereditary disorders.
After birth, kidney defects that cause no symptoms are often discovered when imaging studies are done for other reasons. If doctors suspect a child has a kidney defect, they typically do imaging tests such as ultrasonography Ultrasonography There are a variety of tests that can be used in the evaluation of a suspected kidney or urinary tract disorder. (See also Overview of the Urinary Tract.) X-rays are usually not helpful in evaluating... read more , computed tomography Computed tomography There are a variety of tests that can be used in the evaluation of a suspected kidney or urinary tract disorder. (See also Overview of the Urinary Tract.) X-rays are usually not helpful in evaluating... read more (CT), nuclear scans Nuclear Scans of the Digestive Tract Nuclear scans are tests that involve the use of harmless radioactive materials ( see Radionuclide Scanning). The radioactive materials are ingested as part of a meal or in a drink or are given... read more , or magnetic resonance imaging Magnetic resonance imaging There are a variety of tests that can be used in the evaluation of a suspected kidney or urinary tract disorder. (See also Overview of the Urinary Tract.) X-rays are usually not helpful in evaluating... read more (MRI). Rarely, doctors do intravenous urography Intravenous urography There are a variety of tests that can be used in the evaluation of a suspected kidney or urinary tract disorder. (See also Overview of the Urinary Tract.) X-rays are usually not helpful in evaluating... read more .
Children who have dysplasia may undergo a biopsy of the kidney Kidney biopsy Site-specific biopsies and cell sampling are also used in the evaluation of people with suspected kidney and urinary tract disorders. (See also Overview of the Urinary Tract.) A kidney biopsy... read more (a sample of kidney tissue is removed and examined under a microscope).
People who have polycystic kidney disease may have genetic testing done to help them understand the probability that their children will inherit the disease.
Treatment of Kidney Defects
Sometimes surgical procedures
Sometimes a kidney transplant or dialysis
Treatment of kidney birth defects depends on the specific defect but, in general,
Children who have blockage of urine flow that causes frequent urinary tract infections, pain, damage to the kidney, or other problems may need surgery.
Children whose kidney function is poor may 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 .