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Renal Hypoplasia, From Grossly Insufficient to Not Quite Enough: Consideration for Expanded Concepts Based Upon the
1Arkana Laboratories, Little Rock, AR.
Abstract:
Hypoplasia is defined in the Merriman-Webster dictionary as "a condition of arrested development in which an organ, or part, remains below the normal size, or in an immature state." The degree of reduced size is not definitional. Renal hypoplasia, however, has historically been defined as a more marked reduction in renal mass such that presentation in childhood is the norm. There are 3 commonly recognized types of renal hypoplasia, simple hypoplasia, oligomeganephronic hypoplasia (oligomeganephronia) and segmental hypoplasia (Ask-Upmark kidney). They have in common a reduction in the number of renal lobes. A fourth type, not widely recognized, is cortical hypoplasia where nephrogenesis is normal but there is a reduction in the number of nephron generations. Recently there has been great interest in milder degrees of reduced nephron mass, known as oligonephronia because of its association with risk of adult-onset hypertension and chronic kidney disease. Since the last pathology review of this topic was published by Jay Bernstein in 1968, an update of the renal pathology findings in renal hypoplasia is provided with a review of 18 new cases. The renal hypoplasias are then framed within the modern concept of oligonephronia, its diverse causes and prognostic implications.
Insights
Renal hypoplasia, a reduced kidney mass, encompasses various types including oligonephronia. This condition, characterized by fewer nephrons, is linked to adult-onset hypertension and chronic kidney disease, necessitating updated pathology reviews.
Area of Science:
- Nephrology
- Pathology
- Developmental Biology
Background:
- Renal hypoplasia involves arrested development leading to reduced kidney size.
- Historically, it implies significant renal mass reduction, often presenting in childhood.
- Recognized types include simple, oligomeganephronic, and segmental hypoplasia, all involving fewer renal lobes.
Purpose of the Study:
- To provide an updated review of renal hypoplasia pathology.
- To frame renal hypoplasias within the modern concept of oligonephronia.
- To discuss the diverse causes and prognostic implications of reduced nephron mass.
Main Methods:
- Review of 18 new cases of renal hypoplasia.
- Analysis of renal pathology findings.
- Comparison with historical definitions and recent research on oligonephronia.
Main Results:
- Identified three commonly recognized types of renal hypoplasia (simple, oligomeganephronic, segmental) and a less recognized type (cortical).
- Highlighted the growing interest in milder forms of reduced nephron mass (oligonephronia).
- Presented updated pathology findings based on new cases and literature.
Conclusions:
- Renal hypoplasia is a spectrum of conditions with reduced nephron number or mass.
- Oligonephronia, a milder form, has significant associations with adult-onset hypertension and chronic kidney disease.
- Updated pathological understanding is crucial for recognizing diverse causes and prognostic implications.
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