Encyclopedia
Congenital anomalies of kidney and urinary tract (CAKUT) is a group of abnormalities affecting the kidneys or other structures of the urinary tract. The additional parts of the urinary tract that may be affected include the bladder, the tubes that carry urine from each kidney to the bladder (the ureters), and the tube that carries urine from the bladder out of the body (the urethra). CAKUT results from abnormal development of the urinary system and is present from birth (congenital), although the abnormality may not become apparent until later in life.
- genetic conditions
1. Introduction
Individuals with CAKUT have one or more kidney or urinary tract abnormalities. For paired structures, like the kidneys and ureters, one or both may be affected. Many different developmental abnormalities are classified as CAKUT, including underdevelopment or absence of a kidney (renal hypodysplasia or agenesis), a kidney formed of fluid-filled sacs called cysts (multicystic dysplastic kidney), buildup of urine in the kidneys (hydronephrosis), an extra ureter leading to the kidney (duplex kidney or duplicated collecting system), a blockage in a ureter where it joins the kidney (ureteropelvic junction obstruction), an abnormally wide ureter (megaureter), backflow of urine from the bladder into the ureter (vesicoureteral reflux), and an abnormal membrane in the urethra that blocks the flow of urine out of the bladder (posterior urethral valve).
CAKUT varies in severity. The abnormalities can result in recurrent urinary tract infections or a buildup of urine in the urinary tract, which may damage the kidneys or other structures. Severe CAKUT can result in life-threatening kidney failure and end-stage renal disease.
CAKUT is often one of several features of a condition that affects multiple body systems (syndromic CAKUT). For example, renal coloboma syndrome, 17q12 deletion syndrome, renal cysts and diabetes (RCAD) syndrome, Fraser syndrome, Townes-Brocks syndrome, and branchio-oto-renal syndrome can cause kidney or urinary tract abnormalities in addition to other problems. However, urinary system abnormalities sometimes occur without other signs and symptoms, which is known as nonsyndromic or isolated CAKUT.
2. Frequency
CAKUT is estimated to occur in 1 in 100 to 500 newborns. These abnormalities are the most common cause of end-stage renal disease in children.
3. Causes
The causes of CAKUT are complex. It is likely that a combination of genetic and environmental factors contribute to the formation of kidney and urinary tract abnormalities.
The genetic factors involved in most cases of CAKUT are unknown. Syndromic CAKUT is caused by changes in the genes associated with the particular syndrome. Variations in these same genes can also underlie some cases of isolated CAKUT. The genes most commonly associated with isolated CAKUT are PAX2, which is also associated with renal coloboma syndrome, and HNF1B, which is involved in 17q12 deletion syndrome and RCAD syndrome. These two genes play critical roles in the formation of the kidneys, urinary tract, and other tissues and organs during embryonic development. Certain mutations in these genes are thought to disrupt development of the kidneys or other parts of the urinary tract before birth, leading to CAKUT. Mutations in many other genes involved in development of the urinary system have also been associated with isolated or syndromic CAKUT.
Research shows that the same genetic mutation can lead to different kidney or urinary tract abnormalities, even among members of the same family. It is likely that additional changes in other genes help determine how the condition develops and how severe it is. In addition, environmental factors may influence development of CAKUT. The risk of CAKUT is higher in babies whose mothers had diabetes; took certain medications that are harmful to the kidneys, such as some anti-seizure drugs; or lacked certain vitamins and minerals, such as folate and iron, during pregnancy.
4. Inheritance
Inheritance of CAKUT is complex and not completely understood. About 10 to 20 percent of cases are thought to occur in families. When inherited, CAKUT most commonly follows an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause an abnormality. However, some people who have the altered gene never develop CAKUT, a situation known as reduced penetrance.
Less commonly, CAKUT follows an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not have signs or symptoms of the condition.
In many cases, the inheritance pattern is unknown or the condition is not inherited. In some of these cases, a new (de novo) mutation in the gene that occurs during the formation of reproductive cells (eggs or sperm) in an affected individual's parent or in early embryonic development may underlie the urinary system abnormality. These cases occur in people with no history of the disorder in their family.
5. Other Names for This Condition
- CAKUT
This entry is adapted from the peer-reviewed paper https://medlineplus.gov/genetics/condition/congenital-anomalies-of-kidney-and-urinary-tract
References
- Capone VP, Morello W, Taroni F, Montini G. Genetics of Congenital Anomalies ofthe Kidney and Urinary Tract: The Current State of Play. Int J Mol Sci. 2017 Apr 11;18(4). pii: E796. doi: 10.3390/ijms18040796. Review.
- Hwang DY, Dworschak GC, Kohl S, Saisawat P, Vivante A, Hilger AC, Reutter HM, Soliman NA, Bogdanovic R, Kehinde EO, Tasic V, Hildebrandt F. Mutations in 12known dominant disease-causing genes clarify many congenital anomalies of thekidney and urinary tract. Kidney Int. 2014 Jun;85(6):1429-33. doi:10.1038/ki.2013.508.
- Nicolaou N, Renkema KY, Bongers EM, Giles RH, Knoers NV. Genetic,environmental, and epigenetic factors involved in CAKUT. Nat Rev Nephrol. 2015Dec;11(12):720-31. doi: 10.1038/nrneph.2015.140.
- Sanna-Cherchi S, Westland R, Ghiggeri GM, Gharavi AG. Genetic basis of humancongenital anomalies of the kidney and urinary tract. J Clin Invest. 2018 Jan2;128(1):4-15. doi: 10.1172/JCI95300.
- Vivante A, Kohl S, Hwang DY, Dworschak GC, Hildebrandt F. Single-gene causesof congenital anomalies of the kidney and urinary tract (CAKUT) in humans.Pediatr Nephrol. 2014 Apr;29(4):695-704. doi: 10.1007/s00467-013-2684-4.
- Weber S, Moriniere V, Knüppel T, Charbit M, Dusek J, Ghiggeri GM, JankauskienéA, Mir S, Montini G, Peco-Antic A, Wühl E, Zurowska AM, Mehls O, Antignac C,Schaefer F, Salomon R. Prevalence of mutations in renal developmental genes inchildren with renal hypodysplasia: results of the ESCAPE study. J Am Soc Nephrol.2006 Oct;17(10):2864-70.
