Congenital anomalies of kidney and urinary tract

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.

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.