Renal Agenesis Health Article

Genetic profile

Bilateral renal agenesis (BRA) is a rare condition thought to occur in sporadic and autosomal recessive forms. Sporadic forms of BRA have an unknown cause that may or may not be genetic. It is thought that BRA can be inherited in an autosomal recessive form, caused by the inheritance of two defective copies of a gene. Each parent contributes one copy of a gene. In autosomal recessive inheritance, if both copies are defective, the result is disease. If only one defective copy is present, the disease does not occur, but the defective gene can still be passed on to subsequent generations. If both parents are carrying a defective gene, each offspring has a one in four (25%) chance of inheriting the disease. Populations with a high frequency of healthy individuals carrying defective genes will also have higher prevalence of offspring with the disease.

BRA is also more common when a parent has a distinct kidney malformation, especially unilateral renal agenesis. Research has demonstrated that unilateral renal agenesis and bilateral renal agenesis are genetically related. For this reason, when bilateral renal agenesis is detected in an infant, an ultrasound is performed on the kidneys of parents and siblings. Approximately 9% of first-degree relatives of infants with bilateral renal agenesis have some type of asymptomatic renal malformation.

As of 2005, the exact genetic causes of both unilateral and bilateral renal agenesis are unknown. It is speculated that both conditions are caused by mutations in the genes involved in fetal kidney development. Normal fetal kidney development involves an essential interaction between the forming kidney buds (ureteric bud) and a tissue known as the metanephric mesenchyme. The interaction of the ureteric bud with the metanephric mesenchyme is necessary for kidney formation. The interaction is controlled by a combination of genes, cellular-signaling molecules that control gene expression (transcription factors), and cellular-signaling molecules that control cell growth (growth factors). Animal studies have identified several of the factors that can be mutated to cause renal agenesis. Research is ongoing to determine the cause in humans.

As of 2005, the cutting edge of renal agenesis research is at the Potter syndrome tissue bank where scientists are running experiments on tissue donations from parents of children born with bilateral renal agenesis. Researchers are collecting tissue samples from the neonates and blood samples from family members in an effort to discover the gene mutations responsible for the condition. The Potter syndrome tissue bank is the only one of its kind in the world.

Demographics

Unilateral kidney agenesis is fairly common, occurring in approximately one per 1,000 live births in the United States. Bilateral renal agenesis occurs in one per 3,000 live births. There is no association of renal agenesis with race. Males have a higher rate of developing Potter syndrome than females. Individuals with bilateral renal agenesis present with the condition as neonates, whereas individuals with unilateral renal agenesis may not be aware of their condition even as adults. Unilateral renal agenesis is usually discovered in an adult undergoing tests for some other condition.

Prognosis

In the absence of kidney injury or disease, the prognosis for unilateral renal agenesis is excellent. Individuals with unilateral renal agenesis usually lead normal, healthy lives. Avoidance of injury and basic health practices are important to maintain this quality of life.

Bilateral renal agenesis has a very poor prognosis. It is usually fatal in the first few days of life. The usual cause of death is respiratory failure and acute renal failure during the neonatal period. If survival progresses to early childhood, patients may have chronic lung disease or chronic renal failure. If the lungs have sufficient development, a kidney transplant is necessary for survival. After a kidney transplant, the prognosis is improved.

BOOKS

Moore, Keith L., and T. V. N. Persaud. The Developing Human, Clinically Oriented Embryology, Seventh Edition. St. Louis, MO: Elsevier Science, 2003.

WEBSITES

Parent Permission for Participation in the Potter Syndrome Tissue Bank. (April 14, 2005.) <http://potterssyndrome.org/bendonconsent.html>.

Sairam, Vellore K., Luther Travis. "Potter Syndrome." E-medicine. April 1, 2003 (April 14, 2005). <http://www.emedicine.com/ped/topic1878.htm>.

"Solitary Kidney." National Kidney and Urologic Diseases Information Clearinghouse. May 2004 (April 14, 2005). <http://kidney.niddk.nih.gov/kudiseases/pubs/solitarykidney/>.

ORGANIZATIONS

National Kidney and Urologic Diseases Information Clearinghouse. 3 Information Way, Bethesda, MD 20892-3580. (800) 891-5390. E-mail: nkudic@info.niddk.nih.gov. (April 22, 2005.) <http://kidney.niddk.nih.gov/about/index.htm>.

Potter's Syndrome Support Group Main Forum. (April 22, 2005.) <http://forums.delphiforums.com/n/main.asp?webtag=potterssyndrome&nav=start&prettyurl=%2Fpotterssyndrome%2Fstart>.

Maria Basile, PhD