S DAVIS1, K MURALI1, K LAMBERT3, D HUBER2
1The Wollongong Hospital, Illawarra Shoalhaven Health Service, Wollongong, Australia, 2South Coast Vascular Centre, Wollongong, Australia, 3Centre for Health Research Illawarra Shoalhaven Population (CHRISP), Wollongong, Australia
Aims: To evaluate whether elevated Renal Resistive Index (RRI) predicts the presence and progression of chronic kidney disease (CKD) after adjusting for comorbidities.
Background: Renal Doppler ultrasonography (RDU) is primarily used to evaluate renal perfusion. Renal Resistive Index (RRI) – a measure of intra-renal vascular resistance, is routinely reported. Increased RRI is argued to imply renal parenchymal disease and predict risk of CKD progression but this remains contentious.
Methods: This case-control retrospective study included subjects undergoing RDU between 2014-2016. Cases (RRI > 0.7) and controls (RRI ≤ 0.7) were matched for age and gender. The presence of comorbidities: CKD (eGFR <60mls/min), diabetes, hypertension, peripheral vascular (PVD) and ischaemic heart disease (IHD) were recorded for all subjects. Biochemical data was reviewed at five time-points: baseline (time of RDU), 6 months, 1, 2 and 3 years. Patients with established renal artery stenosis, cystic disease, glomerulonephritis and renal transplant were excluded.
Results: The study included 340 patients: 178 cases and 162 controls. Cases had significantly higher odds of having CKD OR: 2.15 (95% CI: 1.18-3.92, p<0.0001) with a significant negative correlation between RRI and eGFR at all time-points. However, elevated RRI did not predict CKD progression.Elevated RRI was strongly associated with diabetes: OR 4.95; (95% CI: 2.39-10.3; p<0.0001); hypertension OR 3.15 (95% CI: 1.33-7.47; p <0.01) and PVD affecting limbs OR: 5.75 (95% CI: 1.71-19.3, p=0.005), but not IHD (p=0.23).
Conclusions: Elevated RRI is associated with CKD and comorbidities: diabetes, hypertension and PVD. It did not predict CKD progression. Prospective studies of longer duration are required to assess its utility as a prognostic marker.
Dr Karumathil Murali
FRACP, MD (Clinical Epidemiology)
Renal Staff Specialist, Illawarra Shoalhaven Health Service
Clinical Associate Professor, The University of Wollongong