A morphometric study of preeclamptic nephropathy with focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is observed in severe or atypical preeclamptic patients biopsied postpartum. To further define the structural characteristics that might be related to atypical clinical manifestations in this disorder, we analyzed the postpartum renal biopsies of eight preeclamptic patients with FSGS by morphometry and studied the structural-functional relationships. For comparison, three postpartum biopsies with primary FSGS and eight nonpregnant subjects with primary FSGS were also studied. Mesangial volume fraction was increased in the preeclamptic FSGS group being 2 times that of the pregnant or nonpregnant primary FSGS group. Mean surface density of peripheral glomerular basement membrane (PGBM) per glomerulus was markedly decreased in the preeclampsia group being 1/3 that for the pregnant or nonpregnant primary FSGS group. Volume density of cortical interstitium in the preeclamptic FSGS was smaller than that of the primary FSGS group. In preeclamptic FSGS, mesangial volume fraction correlated inversely with PGBM surface area (r = -0.84; p < 0.01) and with creatinine clearance (Ccr) (r = -0.63; p < 0.05). PGBM surface area per glomerulus in preeclamptic FSGS correlated with Ccr (r = +0.63; p < 0.05). Mean volume density of cortical interstitium was not related to Ccr nor with the percentage of glomeruli with FSGS in preeclamptic FSGS. These results suggest that decreased glomerular filtration function in atypical preeclampsia is linked to decreased PGBM surface area, that results from mesangial expansion and particularly from mesangial interposition.