Systemic Microvasculature Frailty: Brain frailty score predicts contrast-associated acute kidney injury after thrombectomy for stroke

BACKGROUND: Contrast-associated acute kidney injury (CA-AKI) is a frequent complication after mechanical thrombectomy (MT). Cerebral small vessel disease (CSVD) reflects cerebral microvascular dysfunction driven by systemic vascular risk factors that also affect renal integrity, and may therefore serve as a surrogate marker of renal vulnerability. METHODS: We prospectively included 351 patients with anterior circulation large-vessel occlusion who underwent MT. Baseline non-contrast CT was used to derive the modified small vessel disease (mSVD) score and the Brain Frailty Score (BFS). CA-AKI was defined as ≥ 0.5 mg/dL or ≥ 25 % increase in serum creatinine within 48-72 h after MT. Multivariable logistic regression, Firth penalized models, and XGBoost machine learning identified independent predictors. RESULTS: CA-AKI occurred in 42 patients (12.0 %). Affected patients were older (68 vs. 62 years), had higher glucose (143 vs. 118 mg/dL), elevated systolic pressure, and more pronounced CSVD features. Severe BFS (score=3) independently predicted CA-AKI (OR=5.13; 95 % CI 1.46-91.28; p = 0.039) after adjustment for age, glucose, and recanalization, whereas mSVD and individual imaging markers were not significant. The final model showed good discrimination and calibration (AUC=0.73; Brier=0.08) and remained stable in sensitivity analyses. In Firth regression, BFS remained significant (OR=4.26; 95 % CI 1.23-22.54). XGBoost achieved an AUC= 0.84, confirming the consistent predictive relevance of vascular, metabolic, and imaging factors across models. CONCLUSIONS: BFS predicts CA-AKI after thrombectomy, outperforming both conventional CSVD scoring and individual imaging markers. These findings support the concept of Systemic Microvasculature Frailty, in which cerebral microangiopathy reflects global endothelial vulnerability with acute renal implications.