Practice Essentials
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. See the image below.
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.
Signs and symptoms
Oligomeganephronia is usually found in infants in their first year of life and presents with anorexia, vomiting, and failure to thrive.
After the first year of life, individuals with oligomeganephronia most often present with short stature, polyuria and polydipsia, or proteinuria.
See Presentation for more detail.
Diagnosis
Laboratory studies include the following:
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Urinalysis
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Electrolyte, BUN, and creatinine tests
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Calcium, phosphorus, alkaline phosphatase, and parathyroid hormone assessments
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Hemoglobin level or hematocrit
Imaging studies include renal ultrasonography
See Workup for more detail.
Management
Medical care in patients with oligomeganephronia is supportive, including fluid and electrolyte balance, nutritional support, and management of the manifestations of chronic renal failure.
See Treatment and Medication for more detail.
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).
Etiology
Developmental arrest of the metanephric blastema at 14-20 weeks' gestation causes oligomeganephronia.
Although oligomeganephronia is associated with some genetic syndromes, most cases of oligomeganephronia are sporadic. However, mutations in the paired-box transcription factor (PAX2) have been seen even in persons with nonsyndromic oligomeganephronia. Heterozygous PAX2 mutations have been detected in one third of children with oligomeganephronia. [1] Mutations in the homeobox transcription factor (hepatocyte nuclear factor-1 β) have been described in association with oligomeganephronia. Interestingly, the heterozygous mutation may be associated with development of the kidney lesion.
Vascular abnormalities and accidents have been associated with this type of renal hypoplasia. The cause of most oligomeganephronia cases is unknown.
Transcription factor 2 (TCF2) is responsible for numerous malformations that involve the kidneys. [2]
Epidemiology
United States statistics
The 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 statistics
Oligomeganephronia has been primarily reported in France; however, it has also been described in other geographic areas.
Race-, sex-, and age-related demographics
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. International studies have shown a male-to-female ratio of 3:1. [3]
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.
Oligomeganephronia may be suspected prenatally or at any time after birth.
Prognosis
Oligomeganephronia is progressive and results in chronic renal failure and end-stage renal disease (ESRD).
Morbidity/mortality
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.
Complications
Complications of chronic renal disease include growth failure, metabolic bone disease, anemia, metabolic acidosis, and other disorders of fluid and electrolyte metabolism.
Patient Education
Patients with oligomeganephronia and their parents or caregivers need to understand the chronic progressive nature of this condition and the need for long-term follow-up care to maximize growth and to prolong renal function.
If an associated syndrome is present, offer genetic counseling and education to the patient and family.
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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.
