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Pediatrics: General Medicine > Nephrology
Oligomeganephronia
Article Last Updated: May 9, 2007
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: Pascale H Lane, MD, Helen Freytag Distinguished Professor of Pediatrics and Associate Chair for Research, Department of Pediatrics, Section of Nephrology, University of Nebraska Medical Center
Pascale H Lane is a member of the following medical societies: Alpha Omega Alpha, American Association for the Advancement of Science, American College of Physician Executives, American Diabetes Association, American Heart Association, American Physiological Society, American Society of Nephrology, American Society of Pediatric Nephrology, International Society of Nephrology, Juvenile Diabetes Foundation International, and National Kidney Foundation
Editors: Richard Neiberger, MD, PhD, Director of Pediatric Renal Stone Disease Clinic, Associate Professor, Department of Pediatrics, Division of Nephrology, University of Florida College of Medicine and Shands Hospital; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Luther Travis, MD, William W Glauser Professor of Pediatrics and Pediatric Nephrology, Department of Pediatrics, Divisions of Nephrology and Diabetes, University of Texas Medical Branch and Children's Hospital; Howard Trachtman, MD, Program Director, Pediatrics Research, Schneider Children's Hospital, Department of Pediatrics, Division of Nephrology, Professor, Albert Einstein College of Medicine; Craig B Langman, MD, The Isaac A Abt, MD, Professor of Kidney Diseases, Feinberg School of Medicine, Northwestern University; Division Head of Kidney Diseases, Children's Memorial Hospital, Chicago
Author and Editor Disclosure
Synonyms and related keywords:
oligomeganephronic renal hypoplasia, oligomeganephronia, end-stage renal disease, ESRD, chronic renal failure, branchiootorenal syndrome, acrorenal syndrome, tapetoretinal dystrophia, renal atrophy, renal dysplasia, arrested development of the metanephric blastema, spontaneous pneumothorax, short stature, polyuria, polydipsia, proteinuria, acrorenal syndromes
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 a number of 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).
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 reported primarily in France; however, it also has 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.
History
- In neonates, kidney disease is often suspected with spontaneous pneumothorax, feeding problems, or laboratory finding abnormalities.
- 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.
- This condition may be incidentally diagnosed when renal abnormalities are discovered during the course of another illness.
Physical
- Physical examination findings are frequently normal in children with oligomeganephronia.
- In neonates with oligomeganephronia, particular attention should be directed to diagnosis of associated syndromes, including branchiootorenal syndrome, acrorenal syndrome, and tapetoretinal dystrophia.
- Branchiootorenal syndrome is an autosomal dominant disorder that includes preauricular sinus or dimples, abnormally formed ears, branchial fistula, and hearing loss.
- Acrorenal syndromes may occur sporadically or in an autosomal recessive manner; these include ectrodactyly and urinary tract malformations.
- Tapetoretinal dystrophia occurs more frequently with nephronophthisis but has been described with oligomeganephronia.
Causes
- 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. Recently, mutations in the homeobox transcription factor (hepatocyte nuclear factor-1b) 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.
Other Problems to be Considered
Renal atrophy
Renal dysplasia
Simple renal hypoplasia
Lab Studies
- Urinalysis: Proteinuria is often the first laboratory manifestation of oligomeganephronia and precedes decline in renal function by several years.
- Electrolyte, BUN, and creatinine tests: Laboratory manifestations of renal failure are frequently present, including elevated BUN and creatinine levels, hyponatremia, and metabolic acidosis.
- Calcium, phosphorus, alkaline phosphatase, and parathyroid hormone assessments: Advancing renal failure may result in secondary hyperparathyroidism.
- Hemoglobin or hematocrit level: Advancing renal failure may result in anemia due to erythropoietin deficiency.
Imaging Studies
- Renal ultrasonography
- Small kidney size depicted on ultrasonogram usually establishes diagnosis of hypoplasia.
- Follow-up of renal growth has not been demonstrated to be predictive of outcome.
Other Tests
- If specific syndromes are suspected, the following may be useful:
- Hearing tests
- Ophthalmologic evaluation
- Chromosomal studies
Histologic Findings
Exhaustive histologic examination of the kidney is the only way to establish an absolute diagnosis of oligomeganephronia. The number of glomeruli is reduced, and the number of glomerular generations varies from 2-6 (normally ³10). Existing glomeruli and tubules are enlarged, and glomerular diameters of 300-400 nm are common. As the disease progresses, segmental sclerosis and hyalinosis of glomeruli are present. Tubular atrophy with interstitial fibrosis occurs.
Medical Care
- Medical care is supportive, including fluid and electrolyte balance, nutritional support, and management of the manifestations of chronic renal failure.
- Treatment with angiotensin-converting enzyme inhibitors may be of benefit in slowing progression.
Consultations
- Once diagnosis of renal hypoplasia is suspected or established based on renal ultrasonography findings, refer patients to a pediatric nephrologist for ongoing management of chronic renal failure.
Diet
- Dietary recommendations depend on the degree of renal functional impairment.
- Most patients with oligomeganephronia have renal salt wasting and require no restriction of dietary salt or water.
- As renal failure advances, potassium and phosphorus level balance may become problematic and require dietary restrictions.
Activity
- In general, no restriction of normal activity is required. Advise patients with oligomeganephronia to maintain an active, healthy lifestyle.
Treatment is generally supportive and directed at maintaining normal biochemical balance, hemoglobin, and growth. In addition, angiotensin-converting enzyme inhibitors may be of benefit in slowing progression of renal failure, even if the patient has a normal blood pressure. Although angiotensin-converting enzyme inhibitors are mentioned as a potential treatment, they have not been studied sufficiently to provide dosing guidelines.
Further Outpatient Care
- Long-term follow-up care
- Oligomeganephronia is a chronic progressive renal disease that leads invariably to renal failure.
- Assessment of renal function, biochemical status, and growth is necessary to manage this condition and to provide optimal care.
Complications
- Complications of chronic renal disease include growth failure, metabolic bone disease, anemia, metabolic acidosis, and other disorders of fluid and electrolyte metabolism.
Prognosis
- Oligomeganephronia is progressive and results in chronic renal failure and ESRD.
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.
Medical/Legal Pitfalls
- Always consider the presence of a hereditary syndrome, especially in children with other anomalies. Genetic counseling is important in such families.
| Media file 1:
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. |
 |  View Full Size Image | |
Media type: Ultrasound
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Oligomeganephronia excerpt Article Last Updated: May 9, 2007
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