Pre-eclampsia or chronic kidney disease? The flow hypothesis.

Background Chronic kidney disease (CKD) and pre-eclampsia (PE) occur in 3-5% of pregnancies. They often share hypertension and proteinuria and a differential diagnosis may be impossible. However, in PE, the pathogenesis is related to abnormal placentation, which can be detected by abnormal uterine and umbilical Doppler flow velocities, while in CKD, an intrinsic kidney disease is present. We hypothesize that Doppler studies can help to differentiate PE from CKD, as the flow velocities are altered in PE and normal in CKD. Methods We retrospectively selected patients who were followed in our Materno-Foetal Unit (2005-10) and had at least one flow measurement in our setting. CKD patients were included in the presence of proteinuria (≥300 mg/day) and hypertension, mimicking PE. The clinical charts were reviewed by the same operators; the clinical diagnoses were taken as reference. Three flow patterns were considered: alteration of both flow velocity waveforms (FVWs) (uterine and umbilical arteries), hypothesized as predictive of PE; normal FVWs at both levels, hypothesized as predictive of CKD; altered FVW in either artery, considered 'mixed'. Uterine FVWs were considered pathological according to the classical cut-point (RI > 0.58). Umbilical flows were evaluated according to standards adjusted for gestational age. Statistical analysis was performed in SPSS.ResultsThe analysis included 61 cases. The presence of normal FVWs was significantly associated with the diagnosis of CKD (P = 0.0018). Conversely, the presence of both altered flows was significantly associated with PE (P = 0.0233). Conclusions In the presence of proteinuria and hypertension, normal flows suggest CKD altered flows PE. Prospective studies are needed to refine this hypothesis based on the first Doppler criteria supporting the differential diagnosis between CKD and PE.