Congenital Anomalies of Kidney and Urinary Tract CAKUT Renal Agenesis Renal Dysplasia ARPKD Horseshoe Kidney Obstructive Uropathy Cloacal Exstrophy

Congenital anomalies of kidney and urinary tract CAKUT are developmental abnormalities of the kidneys or urinary tract present at birth. They occur due to abnormal embryologic development of the ureteric bud or metanephric blastema. Common examples include renal agenesis, renal dysplasia, autosomal recessive polycystic kidney disease ARPKD, horseshoe kidney, obstructive uropathy, and cloacal exstrophy.

Renal agenesis is a congenital condition in which one or both kidneys fail to develop due to absence of ureteric bud formation during embryogenesis. Unilateral renal agenesis is often asymptomatic with compensatory hypertrophy of the remaining kidney, whereas bilateral renal agenesis causes Potter sequence and is usually fatal due to pulmonary hypoplasia.

Renal dysplasia is a congenital malformation where the kidney develops abnormally with disorganized renal tissue, immature tubules and cysts. Multicystic dysplastic kidney is a common form in which multiple cysts replace normal renal parenchyma, often presenting as an abdominal mass in infants.

Autosomal recessive polycystic kidney disease ARPKD is a genetic disorder caused by mutation in the PKHD1 gene. It leads to bilateral enlarged echogenic kidneys with microscopic cysts in collecting ducts and is often associated with congenital hepatic fibrosis causing portal hypertension.

Horseshoe kidney is a congenital renal fusion anomaly where the lower poles of both kidneys fuse during development forming a horseshoe shape. The fused kidneys remain trapped under the inferior mesenteric artery during ascent and may predispose to urinary tract infections, hydronephrosis and kidney stones.

Obstructive uropathy refers to blockage of urine flow anywhere in the urinary tract leading to hydronephrosis and progressive kidney damage. In children the most common causes include posterior urethral valves, ureteropelvic junction obstruction and ureterovesical junction obstruction.

Cloacal exstrophy is a severe congenital malformation involving failure of the lower abdominal wall and cloacal membrane to close properly. This results in exposed bladder and intestinal segments, imperforate anus and genital abnormalities, requiring complex surgical reconstruction after birth.

Symptoms depend on the specific anomaly but may include abdominal mass, recurrent urinary tract infections, poor urinary stream, hypertension, hematuria, hydronephrosis, renal insufficiency and in severe cases respiratory distress at birth due to pulmonary hypoplasia.

Diagnosis is often made by prenatal ultrasound showing abnormalities such as hydronephrosis or absent kidneys. Postnatal investigations include renal ultrasound, voiding cystourethrogram VCUG, nuclear renal scan, CT scan and laboratory tests to assess kidney function.

Treatment depends on the specific condition and severity. Management may include observation and monitoring, antibiotic prophylaxis for infections, surgical correction of urinary tract obstruction, nephrectomy for nonfunctional kidneys and dialysis or kidney transplantation in severe renal failure.