Renal Hypoplasia, From Grossly Insufficient to Not Quite Enough: Consideration for Expanded Concepts Based Upon the Author’s Perspective With Historical Review

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.

A Homozygous Dab1−/− Is a Potential Novel Cause of Autosomal Recessive Congenital Anomalies of the Mice Kidney and Urinary Tract

“…Sectioning through the yotari mice kidneys revealed a thinner cortex and a significantly smaller mean kidney and PCT, DCT and G diameters compared to wild-type animals. The decrease in kidney size caused by insufficient nephron endowment is known as renal hypoplasia, one of the most common CAKUT disorders, which predisposes adult-onset hypertension and chronic kidney disease [ 31 ]. In addition, the microphotographs captured with the TEM revealed that yotari mice exhibited prominent podocyte damage with foot process effacement and a lack of filtration slits.…”

Renal Hypoplasia: Case Literature Review

“…In this study they had studied the Radial Glomerular Count which employed sections oriented along medullary rays for estimation of number of nephron generations. The glomerular layers on each side of medullary rays were recorded [20].…”

<b><i>PAX2</i></b> Mutation-Related Oligomeganephronia in a Young Adult Patient

“…Conditions leading to glomerulomegaly, such as obesity, diabetes, hypertension, or prematurity, did not exist in our patient. Since she had normal-sized kidneys and the calyces and pelvis did not exhibit alteration, she definitely did not have pediatric type of OMN [ 1 ]. The distinctive biopsy features and the lack of hypertension did not favor the diagnosis of oligonephronia [ 1 ].…”

“…Since she had normal-sized kidneys and the calyces and pelvis did not exhibit alteration, she definitely did not have pediatric type of OMN [ 1 ]. The distinctive biopsy features and the lack of hypertension did not favor the diagnosis of oligonephronia [ 1 ]. The case was concluded as OMN in nonhypoplastic kidney with adaptive FSGS related to PAX2 mutation.…”

“…End-stage renal failure occurs months after birth or until early to mid adolescence. Mutations in PAX2 transcription factor gene can play a role in the etiology of OMN because heterozygous PAX2 mutations have been found in one-third of children with OMN [ 1 , 2 ].…”