Glomerular size in renal dysplasia secondary to obstructive uropathy: A further exploration of the fetal lamb model

Abstract

Background/Purpose: Creating an obstructive uropathy early in glomerulogenesis would produce multicystic dysplastic kidneys (MCDK). Measuring the mean planar area of the glomeruli (GMPA) may clarify the pathogenesis of MCDK. Methods: Fetal lambs at 60 days' gestation had their left ureter ligated and were delivered by cesarian section at 145 days' gestation. Kidney weight and length were recorded. GMPA in 3 zones (outer, middle, inner) of the sectioned kidney was measured using a computerized planimeter. The obstructed kidneys were compared with contralateral unobstructed kidneys. The unpaired Student's t test was used to determine significance. Results: One ewe miscarried. Four of 5 (80%) 60-day lambs survived. All had dysplastic kidneys. Mean kidney weights were 4.3 ± 0.84 g in MCDK and 16.8 ± 3.6 g in controls (P <.05). The GMPA of the outer, middle, and inner zones of the MCDK were 2.7 × 10−3 mm2, 3.2 × 10−3 mm2, and 4.0 × 10−3 mm2, respectively. Controls were 2.8 × 10−3 mm2, 4.4 × 10−3 mm2, and 6.0 × 10−3 mm2. The glomeruli of 60-day fetal kidneys were 3.0 × 10−3 mm2, 6.1 × 10−3 mm2, and 11.0 × 10−3 mm2. MCDK had smaller glomeruli in the inner and middle zones than controls. Conclusion: Fetal glomeruli appear to grow from the inner zone of the kidney. Early urinary tract obstruction stops this growth. J Pediatr Surg 35:1651-1655. Copyright © 2000 by W.B. Saunders Company.