Background
First described in 1962, oligomeganephronia is a type of renal hypoplasia that results from a quantitative defect of the renal parenchyma with a reduced number of nephrons. This condition differs histopathologically from simple hypoplasia, in which the renal mass is reduced but the number of nephrons is normal. Oligomeganephronia may occur as a sporadic defect or in association with numerous syndromes.
Pathophysiology
Oligomeganephronia results from arrested development of the metanephric blastema at 14-20 weeks' gestation, with subsequent hypertrophy of glomeruli and tubules in the kidney. This hypertrophy and hyperfiltration results in further nephron injury and sclerosis. Eventually, this progressive loss of nephrons leads to end-stage renal disease (ESRD).
Epidemiology
Frequency
United States
Exact frequency of oligomeganephronia is difficult to determine. This condition cannot reliably be clinically distinguished from simple hypoplasia or hypoplasia with dysplasia unless the entire kidney is examined after nephrectomy or at autopsy. In the US Renal Data System, all hypoplasias and dysplasias are reported in a single category that accounts for 8.9% of pediatric ESRD. Incidence of end-stage renal failure due to all causes is 15 per 1 million population of persons younger than 20 years.
International
Oligomeganephronia has been primarily reported in France; however, it has also been described in other geographic areas.
Mortality/Morbidity
Oligomeganephronia is a progressive disorder, eventually resulting in chronic renal failure and ESRD. As with all such disorders, complications such as growth failure, metabolic bone disease, anemia, metabolic acidosis, and other disorders of fluid and electrolyte metabolism may occur.
Race
Renal hypoplasia and dysplasia may occur in people of any ethnic background. The US Renal Data System reports that 70.5% of children in this category are white.
Sex
No sex predominance has been reported, although the US Renal Data System shows a slight male predominance (61.3%) for the hypoplasia and dysplasia category.
Age
Oligomeganephronia may be suspected prenatally or at any time after birth.
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Renal sonogram of a newborn with spontaneous pneumothorax, preauricular pits, and branchial cysts. The right kidney was absent, and the left kidney was hyperechoic and hypoplastic. The left kidney's length measured 1.8 cm; kidneys in newborns are normally 4.5 cm.
