[1659] Renal Hypoplasia: A Review of Thirteen Cases of Two Distinct Types

Stephen M Bonsib, Rong Fan, Ramesh Nair. Louisiana State University Health Sciences Center, Shreveport, LA; Riley Children's Hospital, Indianapolis, IN; University of Iowa Hospitals and Clinics, Iowa City, IA

Background: Renal hypoplasia (RH) is failure of the kidney to achieve normal size. There are several types that include simple hypoplasia - reduced number of lobes, oligomeganephronia - reduced number of lobes with nephron hypertrophy and Ask-Upmark segmental hypoplasia - reduced lobes with deep cortical grooves representing hypoplastic lobes. Another form not recognized we call cortical hypoplasia; nephrogenesis is normal with marked reduction in nephron generations.
Design: The files of SB were searched for cases of RH not associated with cystic dysplasia or extrarenal malformations. Thirteen cases were identified. The glass slides (13/13), gross photographs (6/13) and medical records (11/13) were reviewed. Nephron generations were counted along medullary rays optimally oriented perpendicular to the capsule.
Results: Thirteen cases of RH included 7 segmental hypoplasia (SegH), 5 cortical hypoplasia (CortH) and 1 with mixed features. All were unilateral. Patients presented with normal creatinine. The hypoplastic cortex in SegH contained a vascular scaffold with thick arteries and numerous veins. Infrequent tubules and no glomeruli occurred in 6/7. One case contained a few normal appearing nephrons. Medullary tissue was absent or consisted of a few tubules in 3/7, or consisted of small islands of immature ducts with ER +/- PR positive mesenchymal collars in 4/7. The CortH cases contained normal appearing lobes with normal labyrinth-medullary ray architecture. Radial nephron counts ranged from 2 to 7 nephron generations per lobe in some or all sections (normal 10-12 generations). The outer medulla appeared normal in 5/5 but the inner medulla lacked thin loops of Henle with increased mesenchymal tissue in 3/3. The mixed case had lobes with CortH while others showed SegH.
Conclusions: (1) Renal hypoplasias are uncommon and rarely reported; this abstract illustrate 2 types (2) Patients had normal renal function since most of the affected kidney is normal and the process is unilateral (4) In SegH the nonhypoplastic lobes are normal. The hypoplastic lobes retain a vascular scaffold of a lobe but lack nephrons. Medullary islands of immature ducts implicate ampullary bud in pathogenesis. (5) We describe 5 cases of CortH, a form not previously described where cortical architecture and nephrons appear normal but with reduced nephron generations indicating premature cessation of nephrogenesis. Either ampullary bud or renal blastema causes may be responsible.
Category: Kidney (does not include tumors)

Tuesday, March 20, 2012 11:30 AM

Platform Session: Section H, Tuesday Morning

 

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