Through the combination of a renal biopsy technique modified for pregnant women, electron microscopy, and knowledge of fine (ultramicroscopic) glomerular anatomy, the pathology of the renal glomerular lesion of toxemia of pregnancy (preeclampsia-eclampsia) has been defined. The lesion is pathognomonic and consists of swelling of the cytoplasm of the endothelial cell, deposits underneath the basement membrane and within the swollen endothelial cytoplasm, and an increase of intercapillary cells. The lesion reduces the glomerular capillary lumen. It is the most sensitive pathological lesion of toxemia in the body, and is present in all cases of toxemia. Once formed, the lesion persists until evacuation of the uterus, in spite of apparent clinical improvement with therapy.
The lesion accounts for the characteristically decreased glomerular filtration rate in toxemia, and this may be a factor in the formation of edema. Demonstration of the lesion is the only laboratory method that can reliably differentiate toxemia from uncomplicated essential hypertension (preeclampsia may be superimposed on essential hypertension): the presence of the glomerular lesion indicates toxemia, while absence of the lesion indicates that the illness is not due to toxemia. A severe glomerular lesion indicates impending fetal death.
Although renal biopsy is mainly of investigative use in obstetrics, it is a valid diagnostic tool for discovering or dismissing the possibility of chronic renal disease.
- © 1964 American Heart Association, Inc.