There are many birth defects that involve the genitals and urinary tract. These defects can affect the kidneys (organs that filter wastes from the blood and form urine), ureters (tubes leading from the kidneys to the bladder), bladder (sac that holds urine), urethra (the tube that drains urine out of the body from the bladder), and the male and female genitals. For boys, the genitals include the penis, prostate gland and testes. For girls, the genitals include the vagina, uterus, fallopian tubes and ovaries.

Abnormalities of the genitals and urinary tract are among the most common birth defects, affecting as many as 1 in 10 babies. Some of these abnormalities are minor problems that may cause no symptoms (such as having two ureters leading from one kidney to the bladder), and go undiagnosed unless the child has an X-ray, ultrasound examination or surgery for a related or unrelated problem. Other abnormalities can cause problems such as urinary tract infections, blockages, pain, and kidney damage or failure.

What is the cause of genital and urinary tract defects?



A few genital and urinary tract defects or disorders are inherited from parents who have the disorder or carry the gene for it. Specific causes of most of these conditions are unknown, however. Genetics and environmental factors presumably play various roles during development of these organs. A family with an affected child should consult a genetic counselor, geneticist or a physician who is familiar with genetic disorders. These experts can discuss what is known about the cause of the specific defect and what the risks may be that the defect or disorder will occur again in subsequent offspring.

How are urinary tract defects diagnosed?



Many urinary tract defects can be diagnosed before or after birth with an ultrasound examination, which uses sound waves to examine internal organs of the fetus. After birth, ultrasound and/or a number of other tests may be recommended to provide more information on how well the kidneys and other urinary tract structures are functioning.

What are the most common urinary tract defects?



Some of the most common urinary tract defects include: renal agenesis, hydronephrosis, polycystic kidney disease, multicystic kidneys, low urinary tract obstruction, bladder exstrophy and epispadias, hypospadias and ambiguous genitals.

What is renal agenesis?



Renal agenesis is the absence of one or both kidneys. About 1 in 4,000 babies is born with neither kidney (bilateral renal agenesis). Tragically, about one-third of these babies are stillborn and the rest die in the first days of life. There is no treatment that can save them.

Babies with bilateral renal agenesis often have birth defects affecting other organs, such as the heart and lungs. A fetus that has no kidneys cannot produce urine, a major part of the amniotic fluid that is crucial for normal fetal lung expansion and development. Therefore, most of these deaths result from underdeveloped lungs. Lack of amniotic fluid also contributes to the abnormal facial features and limb defects seen in these babies.

Up to 20 times as many babies (about one in 550) are born with a single kidney (unilateral renal agenesis). These babies often can live normal lives, although they may be at increased risk for kidney infections, kidney stones, high blood pressure and kidney failure. Some affected babies, however, have other birth defects involving the urinary tract, genitals or other organs. These children may face a variety of health problems, depending upon the specific birth defects involved.

What is hydronephrosis?



Hydronephrosis involves swelling of one or both kidneys, with accumulation of urine that cannot flow out of the kidney(s) because of a blockage somewhere in the urinary tract. Significant hydronephrosis is diagnosed in about 1 in 500 pregnancies during a prenatal ultrasound examination.

The blockage that causes hydronephrosis often is caused by a flap of tissue near where urine empties from the bladder (posterior urethral valves). In severe cases, the fetus's bladder becomes swollen with urine, and the urine backs up and may damage or destroy the kidneys. When hydronephrosis is diagnosed before birth, the doctor will monitor the fetus with repeated ultrasound examinations to see if the condition is worsening. Some babies with severe hydronephrosis are sick at birth, with breathing problems, urinary tract infections and kidney failure. Once these problems have been treated, the urinary blockage can be surgically corrected (although some kidney damage may remain). Many mild cases of hydronephrosis resolve without surgery.

Occasionally, hydronephrosis can become life-threatening before birth. In such cases, a small tube called a shunt may be inserted into the fetus's bladder to drain urine into the amniotic fluid until birth, when the blockage can be repaired. Prenatal treatment of these obstructions has been the most successful form of fetal surgery to date.

Urinary blockages also commonly occur where the ureter connects to the kidney (uretero-pelvic junction obstruction). This condition varies in severity, with some cases causing kidney failure in newborns and infants, and others improving without treatment. Surgery often is recommended in the first year or two of life to relieve the obstruction and prevent further kidney damage, urinary tract infections and pain.

What is polycystic kidney disease?



Polycystic kidney disease (PKD) is an inherited disorder that results in the growth of numerous cysts in the kidneys, reduced kidney function and, often, kidney failure. There are two main forms of the disorder: autosomal dominant and autosomal recessive PKD. Besides kidney failure, both forms can cause frequent urinary tract infections, pain, high blood pressure and other problems.

Autosomal dominant PKD is one of the most common genetic disorders, affecting between 1 in 200 and 1 in 1,000 individuals of all ages. It most often is inherited from a parent who has the disease, although up to one-quarter of cases occur in individuals without a family history of the disease. Symptoms usually begin between the ages of 30 and 40, although children can sometimes be affected.

Autosomal recessive PKD is a rare form of the disease that affects children, with cysts sometimes developing before birth. About 1 in 10,000 to 1 in 40,000 babies are born with the disorder. Severely affected babies die in the first days of life, while others with a milder version may live into their teens or twenties. This form of PKD is inherited when both parents (who are unaffected) pass along the gene for the disorder to their child.

Drug treatment can control PKD-related problems such as high blood pressure and urinary tract infections. If kidney failure develops, the patient is treated regularly with a procedure called dialysis that does the kidney's job to cleanse the blood, and sometimes treated with a kidney transplant.

Kidney cysts are a feature of certain other disorders. These include multicystic kidneys, which affect about 1 in 4,000 babies. This disorder, which varies greatly in severity, can cause death in the newborn period when both kidneys are affected. It is believed that multicystic kidneys result from an obstruction in the urinary tract during the early stages of development. Babies with only one affected kidney may have few consequences, such as urinary tract infections. While the affected kidney often does not function (and, in some cases, may need to be removed), an affected child can live a normal life with one healthy kidney.

Kidney cysts also can be a feature of a number of genetic syndromes. In many cases, such cysts cause few or no problems.

What are bladder exstrophy and epispadias?



Bladder exstrophy is a malformation of the bladder in which the bladder is turned inside out and located on the outside of the abdomen. In addition, the skin on the lower abdomen does not form properly, the pelvic bones are widely spaced, and there may be genital abnormalities. Bladder exstrophy, which occurs in about 1 in 30,000 births, affects boys about five times more often than girls.

Epispadias is a related defect involving the urethra and genitals. It often accompanies bladder exstrophy, but may occur by itself. In boys, the urethra often is short and split, with an opening on the upper surface of the penis. The penis itself appears short and flat. In girls, the clitoris may be split, and the urinary opening also is abnormally placed. Up to half of children with epispadias have bladder control problems.

Bladder exstrophy and epispadias can be repaired surgically. Many affected children require a number of surgeries over the first several years of life to achieve bladder control and normal-appearing genitals. In children with bladder exstrophy, the first surgery usually is performed within 48 hours of birth to close the bladder and replace it in the pelvis, close the abdominal wall and bring the pelvic bones into their correct position. Genital repair often is done during this procedure in girls, but repair of the penis usually is done at between the ages of one and two years. Additional surgery to control urine leakage may be done around 3 years of age. Studies show that about 85 percent of affected children can control their bladders following these surgeries.

What is hypospadias?



Hypospadias is a common birth defect of the penis that affects nearly 1 percent of baby boys. The urethra does not extend to the tip of the penis; instead, the opening of the urethra is located somewhere along the underside of the penis.

Hypospadias generally is diagnosed during the newborn examination in the hospital nursery. Affected boys should not be circumcised because the foreskin (which is removed by circumcision) may be needed to help surgically repair the defect. Surgery, which extends the urethra to the tip of the penis, usually is performed between the ages of 9 and 15 months. Without surgery, most affected boys would have to urinate sitting down and, as adults, would suffer pain during intercourse.

What are ambiguous genitals?



Babies who are born with ambiguous genitals have external genital organs that do not appear clearly male or female, or have features of both. For example, a girl may be born with a large clitoris that resembles a penis, or a boy may have testicles with female-like external genitals. An estimated 1 in 1,000 to 1 in 2,000 babies are affected.

There are many causes of ambiguous genitals, including chromosomal and genetic disorders, hormonal disturbances, enzyme deficiencies, and unexplained abnormalities of the fetal tissues that are destined to become the genitals. The most common cause of ambiguous genitals is an inherited disorder called congenital adrenal hyperplasia (CAH) which, in severe forms, also can disturb kidney function and may cause death. CAH involves an enzyme deficiency that causes the adrenal glands to produce excess amounts of male hormones (androgens). The excess androgens cause the clitoris of a girl with CAH to grow too large, resembling a penis. The disorder, which can be diagnosed with blood tests, requires lifelong treatment with the missing hormones. Affected girls may require surgery to correct the appearance of their genitals. (CAH can be diagnosed before birth with a prenatal test called chorionic villus sampling, allowing for prenatal drug treatment that sometimes can prevent genital defects.)

Another common cause of ambiguous genitals is androgen insensitivity syndrome. Affected babies have male chromosomes (XY) but, due to genetic defects, their cells do not respond or respond incompletely to androgens (male hormones). Babies with complete androgen insensitivity have testes (which usually remain inside the abdomen) and female external genitals, although they do not have a uterus or ovaries. These children are almost always raised as girls and have a completely normal female appearance, although they need treatment with hormones to undergo pubertal changes. Babies with partial androgen sensitivity have cells that partially respond to androgens, and often have ambiguous external genitals.

A number of chromosomal abnormalities also can result in ambiguous genitals. These include gonadal dysgenesis, in which the baby has normal male chromosomes (XY), with either female internal and external genital organs, or ambiguous external genitals and some combination of male and female internal organs.

When a child is born with ambiguous genitals, various diagnostic studies need to be done in an attempt to define the baby's gender. These will include physical examination, blood tests (including chromosomal analysis and measurement of the levels of various hormones), urine tests and, sometimes, ultrasound examination or surgery to look at the internal organs. A team of medical specialists will use these tests to help determine whether the baby is developing more like a male or female, and may recommend assigning a gender for the baby. They may then recommend hormone therapy or reconstructive surgery on the genitals. Doctors often recommended that a boy with a very underdeveloped penis and other genital ambiguities undergo reconstructive surgery and be raised as a girl. More recently, in such cases, doctors are somewhat more likely to suggest that the parents raise the child as a girl, but to hold off on surgery to see how the child is developing . and, very importantly, whether the child feels more like a boy or girl. These situations can be extremely difficult for the child and family, so ongoing psychological counseling is strongly recommended.



References



Bernstein, J. The kidneys and the urinary tract, in: Rudolph A.M. et al (eds.), Rudolph's Pediatrics, 20th edition. Stamford, CT, Appleton & Lange, 1996, pages 1347-1405.

Fausto-Sterling, A. The five sexes revisited. The Sciences, July/August 2000, pages 19-23.

Hendricks, M. Into the hands of babes. Johns Hopkins Magazine, September 2000, pages 12-17.

National Institute of Diabetes and Digestive and Kidney Diseases. Polycystic Kidney Disease. NIH Publication No. 96-4008, 1998.

Thomas, D.F.M. Urological Disease in the Fetus and Infant: Diagnosis and Management. Oxford, England, Butterworth Heinemann, 1997.

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