Podocyturia in Pregnancy Gets New Look

Hypertension or preeclampsia during pregnancy, while often asymptomatic, can threaten the health of women and their babies. Two Mayo Clinic studies presented at the ASN’s Kidney Week 2011 provide new information related to these conditions.

Vesna Garovic, MD, and her team examined the potential of a test done mid-pregnancy to predict which women will later develop preeclampsia, a late-pregnancy disorder that is characterized by hypertension and proteinuria that affects 3 percent to 5 percent of pregnancies. Left untreated or without careful monitoring, preeclampsia can lead to serious—even fatal—complications for a pregnant woman and her baby.

The researchers previously showed that podocyturia, the shedding of live kidney cells called podocytes, is present at delivery in patients with preeclampsia. In this study, they tested whether podocyturia is predictive of later development of preeclampsia, and whether it can differentiate among normotensive pregnancies, gestational hypertension, and preeclampsia. For the analysis, urine sediments are cultured for 24 hours to select for viable cells, and podocytes are then identified on the basis of podocin staining.

Among a group of 315 patients in the study, 15 developed preeclampsia and 15 developed gestational hypertension (but not preeclampsia) during pregnancy. All of the patients who developed preeclampsia tested positive for podocyturia in mid-pregnancy (prior to 210 days gestation). None of the study participants with only hypertension tested positive, and none of 44 women with normal pregnancies tested positive.

The test is highly accurate for predicting preeclampsia, which could alert clinicians to take steps to safeguard against the condition in their patients. The test could also differentiate between later development of gestational hypertension and preeclampsia. The high accuracy of this test further supports the role of podocyte loss in the mechanism of proteinuria in preeclampsia.

“Preeclampsia is well recognized as an endothelial cell disease; however, the precise mechanism of proteinuria has remained somewhat elusive,” said Michelle Hladunewich, MD, who was not involved with the research and is a clinical investigator in the divisions of nephrology, critical care, and obstetric medicine at Sunnybrook Health Sciences Center in Toronto. “Although widespread feasibility of the measurement of podocytes in the urine as a predictive marker for preeclampsia is likely limited, these novel insights into the pathophysiology of preeclampsia particularly as it relates to the cross talk between the endothelial cell and the podocyte are most interesting.”

Garovic also led another study that looked at the long-term health effects of hypertensive disorders during pregnancy. Her team identified all female residents of Rochester, Minn., and the surrounding townships in Olmsted County who delivered between 1976 and 1982. The women were categorized into two groups: those with hypertensive disorders during pregnancy and those without. The investigators followed the women after they reached 40 years of age to monitor their heart and kidney health.

A total of 6051 mothers delivered between 1976 and 1982, and 607 women had hypertensive pregnancy disorders at the time while 5444 did not. Follow-up after age 40 years was available for 465 (77 percent) cases and 3898 (72 percent) controls. After the women reached age 40, women who had hypertensive disorders during pregnancy were much more likely to experience hypertension, kidney dysfunction (proteinuria, chronic kidney disease, or end stage renal disease), and strokes than women who did not have hypertensive disorders during pregnancy (51 percent vs. 31 percent, 14 percent vs. 10 percent, and 8 percent vs. 4 percent, respectively).

“Studies of the associations of hypertensive pregnancy disorders with maternal risks for future cardiovascular disease could lead to new guidelines for screening and treatment of women at risk, with the ultimate goal of improving cardiovascular health in women,” Garovic said.

December 2011 (Vol. 3, Number 12)