Renal agenesis

• absence of one or both kidneys.

• Bilateral renal agenesis is uniformly fatal in utero or shortly after birth.

• Unilateral renal agenesis is usually asymptomatic, though it is often associated with other anomalies of the genital tract.

Renal fusion

• May involve some or all portions of each kidney.

• The most common form of renal fusion is the horseshoe kidney, in which the lower poles of each kidney are fused into a single renal mass in the midline.

• Patients are prone to developing obstruction.

Rotational anomalies

• Occur due to failure of the renal pelvis to rotate from an anterior position to a medial position.

• May occur in an otherwise normal kidney or accompany renal fusion or ectopia.

Renal dysplasia

• Refers to a kidney with abnormal development.

• Unilateral disease causes renal enlargement and a flank mass in infancy.

• Bilateral disease is usually fatal.

• Grossly, the kidney may be enlarged and cystic or small and solid.

• histologically, the kidney contains abnormally formed nephron structures, often with cystic change. The presence of fetal cartilage is a characteristic feature.

Pelviureteric junction obstruction

• a common cause of congenital obstructive uropathy.

• Due to an intrinsic malformation of the smooth muscle of the wall of the outflow tract at that site.

• More common in boys.

• Usually unilateral, more common on the left.

• May present in childhood with abdominal pain.

Ureteral duplication

• Common anomaly in which the kidney has two separate renal pelves, accompanied by partial to complete reduplication of the ureter.

• When there is complete reduplication, the upper ureter typically enters the bladder posteriorly at the normal site of the ureteric orifice on the trigone of the bladder. The lower ureter usually enters the bladder laterally with a short intramural course, predisposing it to VUR.

Vesicoureteric reflux

• Failure of the vesicoureteric valve causes abnormal reflux of urine into the ureter when the bladder contracts.

• Predisposes to urinary tract infection (UTi) in children. in severe cases, may be complicated by intra- renal reflux and renal scarring, a condition known as reflux nephropathy .

Posterior urethral valves

 • abnormal mucosal folds in the posterior prostatic urethra that cause obstructive uropathy.

• Their presence is usually indicated when bilateral hydronephrosis is detected on antenatal ultrasound.

 Cryptorchidism

 • Occurs when the testis fails to descend into its normal position in the scrotum.

• Mobilization of the testis and fixation in the scrotum (orchidopexy) should be performed by the age of 2y to preserve fertility.

• Cryptorchidism is important due to its association with a higher risk of testicular germ cell tumours .

Hypospadias

 • The most common anomaly of the penis.

• Refers to the abnormal opening of the urethral meatus on the undersurface of the penis.

• Usually an isolated defect, though the incidence of cryptorchidism appears to be higher in boys with hypospadias.