Oligomeganephronia

Oligomeganephronia is a developmental anomaly of the kidneys, and the most severe form of renal hypoplasia (see this term), characterized by a reduction of 80% in nephron number and a marked hypertrophy of the glomeruli and tubules.

Epidemiology

Prevalence is unknown. The male to female ratio is of 3:1.

Clinical description

Oligomeganephronia is usually detected on routine ultrasound screening with small but normal shaped kidneys. Birth weight is often below the average value. Patients may present at birth with polyuria/polydipsia or signs of renal dysfunction such as anemia. During the first year of life, the usual symptom is persistent anorexia with vomiting, fever, and height-weight growth delay. Renal failure typically occurs during childhood or adolescence. Adult-onset oligomeganephronia has been reported in some rare cases.

Etiology

The etiology of oligomeganephronia is not fully understood, but is hypothesized to be caused by premature termination of nephrogenesis. This may be linked to the same factors as renal hypoplasia, but with a more severe reduction in nephron numbers. Such factors include intrauterine growth restriction, maternal diseases (diabetes, hypertension), maternal drug intake (inhibitors of the renin-angiotensin system or non-steroidal anti-inflammatory drugs (NSAIDs)) or intoxication (smoking and alcohol). Premature birth (before the 36th week) is also a risk factor due to incomplete nephrogenesis. Oligomeganephronia can occur as part of a multi-organ syndrome such as renal coloboma syndrome (see this term), which is caused by mutations in the PAX2 gene (10q24.31), or can be caused by chromosomal disorders including 22q11 deletion syndrome or Wolf-Hirschhorn syndrome (see this term).

Diagnostic methods

Diagnosis can be suspected by bilateral small and echogenic kidneys on ultrasound. CT-scan may, in addition to small normal-shaped kidneys, show a thickened cortex and medulla with striated nephrograms. The diagnosis is confirmed histologically by a reduced number of nephrons, hypertrophic glomeruli with diameters being two to three times the normal size, hypertrophic tubules and thickening of Bowman's capsule. Both kidneys are symmetrically affected.

Differential diagnosis

Differential diagnosis includes renal dysplasia, nephronophthisis, (see these terms), medullary cystic kidney disease, renal infarction or ischemic renal disease, and diffuse renal parenchymal disease.

Antenatal diagnosis

Antenatal ultrasonographic screening is becoming routine and allows detection of oligomeganephronia from midway through gestation.

Genetic counseling

Most cases are sporadic, but familial occurrence has been described.

Management and treatment

Angiotensin-converting-enzyme inhibitors may slow the progression of the disease. Once having reached the stage of terminal renal failure, management includes a dialysis-transplantation program.

Prognosis

With the increasing metabolic demands on the kidney during growth, a decline in renal function is seen resulting in chronic renal failure at a mean age of 10 years (range 6 months to 20 years).