Renal pathology in pre-eclampsia

Pre-eclampsia affects the kidney both functionally and morphologically. Renal haemodynamics decrease and urinary protein excretion increases, in part due to lesions affecting the glomerulus, where a combination of changes produces a characteristic appearance and permits differentiation of pre-eclamptic nephropathy from other glomerular alterations associated with hypertension in pregnancy. In pre-eclampsia the glomerulus is diffusely enlarged and bloodless, due not to proliferation, but to hypertrophy of the intracapillary cells. These alterations, best described ultrastructurally, include hypertrophy of the cytoplasmic organelles in endothelial and occasionally mesangial cells, particularly the lysosomes, which undergo marked enlargement and vacuolization (due to accumulation of free neutral lipids). These reactive changes have been termed 'glomerular capillary endotheliosis'. Other lesions, observed occasionally, include subendothelial and mesangial electron-dense deposits, as well as interposition of mesangial cell cytoplasm or mesangial matrix along an otherwise normal basement membrane. Some investigators have described immunohistological findings (presence of IgM, IgG and fibrin) which they believe specific for pre-eclampsia, and others have claimed the disease may cause focal segmental glomerulosclerosis (FSGS). We believe the immunohistological findings are non-specific and insudative, and that FSGS when present predates the pre-eclamptic complication. Finally, the renal lesions appear fully reversible and the disease has no remote cardiorenal effects on its patients.