PP.23.04] RESPONSES OF THE RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM TO PLASMA VOLUME DEPLETION IN PRE-ECLAMPSIA & SUPERIMPOSED PRE-ECLAMPSIA

Abstract

Objective: Women with chronic kidney disease (CKD) are at increased risk of superimposed pre-eclampsia (SPE) and associated adverse pregnancy outcomes. Diagnosis of SPE using blood pressure and proteinuria is of limited use because these may develop in women with CKD even without the condition. Inaccurate diagnosis may result in unnecessary iatrogenic preterm delivery. Plasma and urinary aldosterone concentrations are elevated in patients with CKD, but suppressed in established pre-eclampsia (PE). The aim of the study was to determine plasma active renin, total plasma and urinary angiotensinogen (AGT) and aldosterone availability in women with CKD with and without SPE compared with normotensive controls (NC) and those with PE without CKD. Design and method: NC women (n = 19), women with PE (n = 14), CKD without SPE (n = 6) and with SPE (n = 11) were recruited from two tertiary antenatal clinics (mean ± SD 38 ± 3 weeks). Active renin and total AGT concentrations were measured by ELISA; urinary tetrahydroaldosterone was measured by gas chromatography-mass spectrometry; creatinine was measured using a standard clinical laboratory assay for normalisation. Results: Aldosterone and plasma active renin (Kruskal Wallis, both P < 0.05) were significantly different between groups. Aldosterone: creatinine ratios were significantly lower in both PE and SPE compared to the NC and women with CKD (median [IQR], PE: 6.5 [3, 14.4]; SPE: 10.8 [5.4, 16.4]; NC: 13.8 [9.1, 29.8]; CKD: 24.2 [16.3, 37.9] μg/mmol creatinine; P < 0.05 for all). Plasma active renin concentrations were also lower in PE, SPE and CKD women compared to NC women (PE: 5.3 [9.7, 21.8]; SPE: 3.4 [2.4, 12]; CKD: 3.9 [3.2, 6.2]; NC: 5.3 [0.2, 8.7] pg/ml; P < 0.05 for all). No differences in either plasma or urinary total AGT were observed between the groups. Conclusions: Women with SPE have lower urinary aldosterone and plasma active renin than women with CKD in keeping with women with PE without pre-existing kidney disease, suggestive of similar pathophysiology. Further exploration of the predictive value of low urinary aldosterone and plasma renin for adverse pregnancy events in women with CKD and its role in cases of diagnostic uncertainty is required.