Glomerular Size in Renal Dysplasia Secondary to Obstructive Uropathy: A Further Exploration of the Fetal Lamb Model

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 x 10(-3) mm(2), 3.2 x 10(-3) mm(2), and 4.0 x 10(-3) mm2, respectively. Controls were 2.8 x 10(-3)mm(2), 4.4 X 10(-3) mm(2), and 6.0 x 10(-3) mmz. The glomeruli of 60-day fetal kidneys were 3.0 x 10(-3) mm(2), 6.1 x 10(-3) mm(2), and 11.0 x 10(-3) mm(2). 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. Copyright (C) 2000 by W.B. Saunders Company.