Below is a concise but complete reference on Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) including the conditions you asked for.
Congenital Anomalies of Kidney and Urinary Tract (CAKUT)
Definition
Congenital anomalies of kidney and urinary tract (CAKUT) are structural abnormalities of the kidneys or urinary tract present at birth due to abnormal embryologic development. They are a major cause of chronic kidney disease (CKD) in children.
Epidemiology
- Occurs in 3–7 per 1000 live births
- Accounts for 30–50% of pediatric end-stage renal disease
- Often detected prenatally by ultrasound
Embryologic Basis
Kidney and urinary tract develop from:
- Metanephric mesenchyme
- Ureteric bud
Abnormal interaction between these structures leads to CAKUT.
1. Renal Agenesis
Definition
Complete absence of one or both kidneys due to failure of ureteric bud development.
Types
- Unilateral renal agenesis
- Bilateral renal agenesis
Pathophysiology
- Failure of ureteric bud → no induction of metanephric blastema → kidney does not develop.
Causes
- Genetic mutations (RET, GDNF)
- Maternal diabetes
- Environmental teratogens
Clinical Features
Unilateral
- Often asymptomatic
- Compensatory hypertrophy of the remaining kidney
- May develop hypertension later
Bilateral
- Severe oligohydramnios
- Potter sequence:
* Flattened face
* Low-set ears
* Pulmonary hypoplasia
* Limb deformities
Investigations
- Prenatal ultrasound
- Postnatal ultrasound
- CT/MRI
- Renal function tests
Management
Unilateral
- Usually no treatment
- Monitor kidney function
- Avoid nephrotoxic drugs
Bilateral
- Usually fatal shortly after birth
2. Renal Dysplasia
Definition
Abnormal kidney development with disorganized renal tissue, cysts, and immature structures.
Types
- Multicystic dysplastic kidney (MCDK)
- Segmental dysplasia
Pathophysiology
Abnormal interaction between ureteric bud and metanephric tissue.
Causes
- Genetic defects
- Urinary tract obstruction during development
Clinical Features
- Often detected prenatally
- Abdominal mass in infants
- Hypertension
- Recurrent urinary tract infections
Investigations
- Ultrasound (multiple cysts)
- DMSA scan
- Renal function tests
Management
- Observation if unilateral
- Treat complications (UTI, hypertension)
- Nephrectomy if symptomatic
3. Autosomal Recessive Polycystic Kidney Disease (ARPKD)
Definition
A hereditary disorder characterized by bilateral enlarged kidneys with numerous microscopic cysts.
Genetics
Mutation in PKHD1 gene.
Pathophysiology
- Dilatation of collecting ducts
- Progressive kidney enlargement
- Associated liver disease (congenital hepatic fibrosis)
Clinical Features
Prenatal / Neonatal
- Enlarged echogenic kidneys
- Oligohydramnios
- Respiratory distress due to pulmonary hypoplasia
Childhood
- Hypertension
- Renal failure
- Hepatomegaly
- Portal hypertension
Investigations
- Prenatal ultrasound
- Kidney ultrasound
- Genetic testing
- Liver function tests
Management
- Supportive care
- Control hypertension
- Dialysis for renal failure
- Kidney transplant
4. Horseshoe Kidney
Definition
Fusion of the lower poles of both kidneys forming a horseshoe shape.
Embryology
Fusion occurs before kidney ascent during development.
Pathophysiology
- Kidney trapped under inferior mesenteric artery
- Abnormal rotation
Clinical Features
Often asymptomatic but may have:
- Recurrent UTIs
- Kidney stones
- Hydronephrosis
- Abdominal pain
Associated Conditions
- Turner syndrome
- Trisomy 18
- Vesicoureteral reflux
Investigations
- Ultrasound
- CT scan
- IV pyelography
Management
- Usually none if asymptomatic
- Treat complications (stones, infection)
5. Obstructive Uropathy
Definition
Structural obstruction of urine flow anywhere in the urinary tract causing hydronephrosis and kidney damage.
Common Causes
- Posterior urethral valves
- Ureteropelvic junction obstruction
- Ureterovesical junction obstruction
- Urethral stricture
Pathophysiology
Obstruction → urine accumulation → increased pressure → renal damage.
Clinical Features
Prenatal
- Hydronephrosis on ultrasound
Postnatal
- Poor urinary stream
- UTIs
- Abdominal mass
- Renal failure
Investigations
- Ultrasound
- Voiding cystourethrogram (VCUG)
- Nuclear renal scan
- Serum creatinine
Management
- Relieve obstruction
- Surgical correction
- Antibiotics for UTIs
- Dialysis in severe cases
6. Cloacal Exstrophy
Definition
A severe congenital malformation where abdominal wall, bladder, and intestines fail to close properly, exposing organs outside the body.
Embryology
Failure of cloacal membrane development.
Pathophysiology
Defect in lower abdominal wall formation during early embryogenesis.
Clinical Features
- Bladder exposed on abdominal wall
- Intestinal segments visible
- Imperforate anus
- Genital abnormalities
- Spinal defects
Associated Conditions
- Omphalocele
- Spinal anomalies
- Limb defects
Diagnosis
- Prenatal ultrasound
- Physical examination at birth
Management
Requires multidisciplinary surgical treatment:
- Neonatal reconstructive surgery
- Bladder reconstruction
- Intestinal repair
- Long-term urologic care
Summary Table
| Disorder | Key Feature | Main Problem |
| -------------------- | ------------------------------ | ---------------------------- |
| Renal Agenesis | Absent kidney | Developmental failure |
| Renal Dysplasia | Cystic malformed kidney | Abnormal tissue organization |
| ARPKD | Bilateral cystic kidneys | Genetic disease |
| Horseshoe Kidney | Fused kidneys | Abnormal migration |
| Obstructive Uropathy | Urine flow blockage | Hydronephrosis |
| Cloacal Exstrophy | Bladder and intestines exposed | Severe developmental defect |
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