Early Ultrasonic Diagnosis of Renal Dysfunction to Detect Cognitive Disorders In Chronic Cerebral Ischemia: A Systematic Review And Meta-Analysis

Abstract

Background: Chronic cerebral ischemia and vascular cognitive impairment are often coupled with systemic microvascular damage. Renal dysfunction may represent a parallel vascular phenotype, and renal ultrasonography (particularly Doppler-derived renal resistive index) has been suggested as a low-burden marker of renal and vascular injury. Objective: This systematic review evaluated whether early ultrasonographic evidence of renal dysfunction can assist in detecting cognitive disorders among adults with chronic cerebral ischemia.

Methods: Searches were designed for PubMed/MEDLINE, Embase, Scopus, Web of Science, PsycINFO, Cochrane CENTRAL, ClinicalTrials.gov, WHO ICTRP, and grey literature sources from inception to 2026-06-17 without language restrictions. Eligible studies included adults with chronic cerebral ischemia, chronic cerebral hypoperfusion, dyscirculatory encephalopathy, cerebral small vessel disease, or vascular cognitive impairment who underwent renal ultrasonography and cognitive assessment.

Results: The search returned 3,059 records, of which 845 duplicates were discarded. After screening 2,214 records, 153 reports were assessed in full text and 139 were excluded. Fourteen evidence records were retained for qualitative synthesis; three were assessed as direct or near-direct renal ultrasound-cognition candidates, but none yielded sufficiently homogeneous extractable data for a valid pooled diagnostic meta-analysis. The only extractable direct renal ultrasound study included 152 participants, 56 with dyscirculatory encephalopathy and renal dysfunction, 55 with dyscirculatory encephalopathy without significant renal insufficiency, and 41 healthy controls. Indirect evidence supported kidney-brain associations, including albuminuria associated with covert infarcts and incident mild cognitive impairment or dementia.

Conclusions: Current evidence supports a biologically plausible kidney-brain microvascular axis, but direct evidence for renal ultrasound as a stand-alone early detector of cognitive disorders in chronic cerebral ischemia remains very low certainty. Prospective studies integrating renal Doppler, renal morphology, albuminuria/eGFR, brain MRI, and cognitive batteries are required.