Estimated glomerular filtration rate in extracranial and intracranial atherosclerotic stenosis among patients with ischaemic stroke: a cross-sectional study

Introduction Kidney dysfunction has been associated with cerebrovascular atherosclerosis, but differences in renal measures between extracranial (ECAS) and intracranial atherosclerotic stenosis (ICAS) remain unclear. Methods This hospital-based cross-sectional study included consecutive patients admitted with acute ischaemic stroke within 14 days of onset between January 2006 and December 2015 who were classified as having the large-artery atherosclerotic subtype. Estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation adapted for Asian populations. Binary logistic regression compared ICAS with ECAS across four eGFR categories. The adjusted category model used complete cases; a sensitivity analysis used 50 multiply imputed datasets for missing covariates. Results Among 1,127 patients with large-artery atherosclerotic stroke, 1,015 had ECAS or ICAS and available eGFR for the category analysis; 755 had complete covariate data. Compared with the highest eGFR category, the lowest two categories had lower adjusted odds of ICAS relative to ECAS in complete-case analyses (OR 0.38, 95% CI 0.21–0.68; and OR 0.50, 95% CI 0.28–0.88) and multiple-imputation analyses (OR 0.35, 95% CI 0.21–0.59; and OR 0.54, 95% CI 0.33–0.88). Proteinuria did not differ significantly between the groups, and eGFR was not significantly associated with stenosis severity within either group. Discussion Lower eGFR was associated with extracranial rather than intracranial stenosis. Mechanistic explanations remain literature-derived and hypothesis-generating. The observational design and absence of diagnostic performance analyses preclude causal inference or conclusions about diagnostic utility or treatment selection.