The kidney

The kidney is the most common site of congenital abnormalities. Some cause no problems but many result in impaired renal function. Renal malformations are often associated with other congenital defects, eg a grossly deformed pinna with ipsilateral abnormalities of the facial bones.

• Renal agenesis:
  • Virtually always unilateral.
  • Kidney is either absent or undeveloped.
  • Usually causes no symptoms and found incidentally.
• Renal hypoplasia:
  • May appear as one small kidney with the other one larger than normal.
  • Small kidneys also have small arteries and are associated with hypertension requiring nephrectomy.
• Supernumerary kidneys:
  • Third kidney is very rare and not to be confused with the relatively common unilateral duplication of the renal pelvis.
• Renal dysplasia and multicystic kidney:
  • Multicystic kidney of the newborn is normally seen in only one kidney as irregularly lobulated mass of cysts and usually absent or atretic ureter.
  • Frequently associated with contralateral abnormalities, especially ureteropelvic junction obstruction.
  • Dysplasia of the renal parenchyma is seen with urethral obstruction or reflux present early in pregnancy or obstructed ureter.
• Adult polycystic kidney disease (links to separate article)
• Infantile polycystic kidneys (links to separate article)
• Simple (solitary) renal cyst:
  • May be inherited or acquired.
  • Significant renal damage is rare and usually only requires continuous follow-up.
• Renal fusion:
  • Prevalence 1 in 1,000 people.
  • Most frequent abnormality seen is a horseshoe kidney containing 2 excretory systems and 2 ureters.
  • Usually asymptomatic but are prone to obstruction.
• Ectopic kidney:
  • In simple ectopy, the kidney does not ascend properly and is found in the pelvis or over the brim.
  • Prone to obstruction and infection.
  • Less commonly crossed ectopy without fusion. The kidney then lies on the opposite side and is not attached to the normally placed kidney.
  • Abnormal rotation: this rarely leads to renal disease.
• Medullary sponge kidney (links to separate article)
• Potter's syndrome (links to separate article)

Abnormalities of the ureter and ureteropelvic junction

These are relatively common and range from complete absence to duplication of the ureter.

• Ureteral atresia:
  • The ureter may be absent or fails to extend to the bladder and therefore with a blind ending.
  • It is associated with ipsilateral absent or multicystic kidney.
  • Bilateral atresia is incompatible with life. Unilateral atresia is usually asymptomatic but may cause hypertension.
• Duplication of the ureter:
  • One of the most common congenital malformations of the urinary tract with duplication found in 0.9% of a series of autopsies.
  • More common in females and is often bilateral.
  • Often asymptomatic but commonly presents with persistent or recurrent urinary tract infections.
• Ureterocele:
  • A sacculation of the bladder end of the ureter that can occur either in the bladder or ectopically.
  • Much more common in girls than in boys.
  • Bilateral in 10% of cases.
  • May be asymptomatic or cause obstruction or incontinence or infection.
• Ectopic urethral orifice:
  • Usually occurs with ureterocele and duplication of the ureter but single ectopic ureters are seen.
  • Boys may present with epididymitis as the ureter drains directly into the vas deferens or seminal vesicle.
  • Girls normally present with incontinence with continual dribbling despite normal voiding.
• Obstruction of the ureteropelvic junction:
  • Common congenital abnormality of the ureter, seen more often in boys than in girls and most cases are unilateral and usually on the left.
  • Nearly always caused by a kink in the ureter where it meets the dilated renal pelvis.
  • Can be diagnosed in utero.
  • In children, normally presents with pain and vomiting.
• Obstructed mega-ureter:
  • Caused by obstruction at the ureterovesical junction.
  • Four times more common in boys than girls and is often bilateral.
  • Often associated with absent or dysplastic contralateral kidney.
  • Usually discovered during prenatal ultrasound.
  • Frequently presents with haematuria, with symptoms of infection and abdominal pain.

Abnormalities of the bladder

• Bladder exstrophy:
  • Absence of the anterior wall of the bladder, with ureters delivering urine into the lower abdomen.
  • Associated with other abnormalities, especially epispadias.
  • Requires surgical reconstruction.
• Persistent urachus:
  • May appear as a draining umbilical sinus and can become infected.
• Contracture of the bladder neck:
  • Common cause of reflux, bladder diverticula and irritable bladder.

Anomalies of the penis and urethra in males

• Apenia:
  • Congenital absence of the penis is very rare.
  • More than 50% of patients have associated genitourinary anomalies, eg cryptorchidism, renal agenesis and dysplasia.
• Megalopenis:
  • The penis enlarges rapidly in childhood due to a high level of production of testosterone.
• Micropenis: the most common aetiologies include:
  • Hypogonadotropic hypogonadism: impaired secretion of gonadotropin-releasing hormone (GnRH) by the hypothalamus occurs in some hypothalamic dysfunctions, eg Kallmann's syndrome, Prader-Willi syndrome.
  • Hypergonadotropic hypogonadism: testes are functionally impaired, eg gonadal dysgenesis.
  • Idiopathic micropenis: normal hypothalamic-pituitary-testicular endocrine function.
• Urethral stricture:
  • Uncommon; the two most common sites are the fossa navicularis and the membranous urethra.
  • Severe cases can result in damage to the bladder and hydronephrosis due to back pressure of urine.
• Posterior urethral valves:
  • Relatively frequent obstructive lesion in male neonates and infants.
  • They are found at the distal prostatic urethra and mucosal folds, looking like thin membranes and causing varying degrees of obstruction when attempting to urinate.
  • Boys usually present with a poor, intermittent, dribbling stream with frequent infection.
• Hypospadias:
  • Urethral meatus is found on the underside of the penis.
  • Occurs in 1/300 male births.
  • Most cases occur on the distal penis or corona.
  • Young children seldom report symptoms but older children and adults may complain of difficulty in directing the urinary stream, and spraying.
• Epispadias:
  • Consists of a defect of the dorsal wall of the urethra.
  • The extent of the defect can vary from a mild glandular defect to complete defects as are observed in bladder exstrophy and/or diastasis of the pubic bones.
  • Epispadias occurs in 1 in 120,000 males and 1 in 450,000 females.
  • The urethra is displaced dorsally so that it opens on to the top of the penis in males.
  • Females have a bifid clitoris and separation of the labia.
  • Incontinence is a common problem.

Female anomalies

• Distal urethral stenosis:
  • Occurs in young girls with enuresis with slow and interrupted stream and recurrent infection.
  • Associated with secondary spasm of the external sphincter.
• Labial fusion:
  • Fused labia minora can present with recurring urinary infection as a result of obstruction to the urine flow.
• Clitoral hypertrophy:
  • Caused by fetal exposure to androgens, usually caused by congenital deficiencies of adrenal enzymes of cortisol synthesis.
  • May also rarely be due to in utero exposure to progestational agents or idiopathic virilisation.

Anomalies of the testis

• Hypogonadism:
  • Small testes with lack of development of secondary sexual characteristics, lack of libido and potency.
  • Characteristically, patients are tall with long extremities.
  • Also associated with Klinefelter's syndrome.
  • Also associated with physiological problems and low intelligence.
• Ectopy and cryptorchidism:
  • Ectopy: testis has not followed normal path of descent. By far the most common site is superficial inguinal.
  • Cryptorchidism: testicular descent is arrested. Cryptorchidism is common, especially unilaterally. At birth, it affects 3.4% boys (30% in prematurity). Half of these descend by the end of first month of life.
• Spermatocele:
  • Painless cystic mass found just above or posterior to the testis.
  • Mostly <1 cm in diameter and usually requiring no therapy.
• Varicocele:
  • Found in around 10% of young men as dilatation of the pampiniform plexus (spermatic venous plexus).
  • Presents as a mass of dilated, tortuous veins and is often tender, usually on the left side.
  • May cause testicular atrophy and decrease sperm concentration and motility.
• Hydrocele:
  • Excess of fluid between the two layers of the tunica vaginalis in young boys.
  • Presents as cystic mass which is often more tense at night.

Chromosomal syndromes^[1]

• Turner's syndrome (links to separate article).
• Other syndromes of gonadal dysgenesis:
  • These range from bilateral streaks or bilateral dysgenetic testes to apparently normal testes.
  • May be asymmetrical, eg streaked one side, normal the other. This is mixed gonadal dysgenesis.
• True hermaphroditism:
  • Characterised by simultaneous presence of both ovarian and testicular tissue.
  • Can occur with an ovary and testis on separate sides or mixed together on same side.
  • External genitalia may appear normal but are often ambiguous with cryptorchidism and hypospadias common.
  • If a testis or ovotestis is present it may be in the inguinal canal, labioscrotal folds or abdomen. The uterus is often present.
  • Associated with 46, XX in 60%, 46, XY in 20% and the remainder have mosaicism or 46, XX/46, XY chimerism.
• Female pseudohermaphroditism:
  • The patient has ovaries with ambiguous external genitalia.
  • Frequently associated with congenital adrenal hyperplasia.
  • Also results from masculinisation due to maternal administration of testosterone or similar.
• Male pseudohermaphroditism:
  • Has testes but without complete masculinisation of genital tract.
  • May be due to defective testicular differentiation or abnormalities in testosterone.

Management of ambiguous genitalia and intersex

See separate article Ambiguous Genitalia.