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

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 kidney dysfunction. During the first year of life, the usual symptom is persistent anorexia with vomiting, fever, and growth delay. Chronic kidney disease typically occurs during childhood or adolescence. Adult-onset oligomeganephronia has been reported in some rare cases.

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, 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.

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 includes renal dysplasia, nephronophthisis, autosomal dominant tubulointerstitial kidney disease, kidney infarction or ischemic kidney disease, and diffuse kidney parenchymal disease.

Antenatal ultrasonographic screening allows detection of oligomeganephronia from midway through gestation.

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

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

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