A NOVEL LINK: REDUCED KIDNEY FUNCTION IS ASSOCIATED WITH CEREBRAL VENTRICULAR ENLARGEMENT MEASURED BY EVANS INDEX

Patients with chronic kidney disease (CKD) have an increased risk of developing idiopathic normal pressure hydrocephalus (iNPH). However, the detailed relationship between the degree of kidney dysfunction and cerebral ventricular enlargement has not been fully elucidated. We investigated the association between kidney function and the Evans Index (EI), a quantitative radiological marker of ventricular size, in a large cohort of patients who underwent brain computed tomography (CT).

This retrospective cross-sectional observational study included all consecutive inpatients and outpatients who underwent brain CT at our institution between January 1, 2022, and December 31, 2024. Duplicate cases were excluded.
EI was calculated as the ratio of the maximal width between the frontal horns of the lateral ventricles to the maximal internal skull diameter on the same axial slice.
The estimated glomerular filtration rate (eGFR) obtained on the day of brain CT, or from the closest available laboratory data within ±3 months, was used as an indicator of kidney function. Because eGFR values were derived from temporally corresponding blood chemistry data, patients with acute kidney injury (AKI) were also included, whereas those with extremely severe AKI resulting in eGFR <5 mL/min/1.73 m² were excluded.
To minimize the influence of extreme outliers on regression analyses, eGFR values ≥90 mL/min/1.73 m² were truncated to 90, in accordance with epidemiologic conventions to prevent overestimation in the normal–high range and to stabilize model estimates. For patients on maintenance hemodialysis (HD), a nominal eGFR of 5.0 mL/min/1.73 m² was assigned to represent minimal residual kidney function, and HD status was additionally modeled as an indicator variable. This substitution was applied solely for analytical consistency and does not represent a measured physiologic value.
Additional variables included the use of antihypertensive, antidiabetic, lipid-lowering, and antiplatelet/anticoagulant medications.
Patients younger than 20 years, those on peritoneal dialysis, and those with intracranial hemorrhage, tumor, prior craniotomy, known hydrocephalus, ventriculoperitoneal shunt, prior coil embolization, chronic subdural hematoma, or cardiopulmonary arrest (CPA) were excluded. Cases in which the frontal horns appeared linearly and could not be reliably measured were also excluded.
Multiple linear regression analyses were performed with EI as the dependent variable.

A total of 1,693 patients (mean age, 72.5 ± 15.1 years; 47.3% male), including 104 on maintenance HD, were analyzed (Table 1). The mean EI was 0.284 ± 0.036, and the mean eGFR was 60.4 ± 24.0 mL/min/1.73 m².

Simple linear regression demonstrated a significant inverse correlation between eGFR and EI (r = −0.330, p < 0.001).
After adjustment for age, sex, the use of antidiabetic, lipid-lowering, and antiplatelet/anticoagulant medications, and HD status, lower eGFR remained an independent predictor of higher EI (standardized β = −0.150, p < 0.001).
Age (β = 0.399, p < 0.001), male sex (β = 0.171, p < 0.001), lipid-lowering drug use (β = −0.069, p = 0.002), and HD (β = 0.058, p = 0.03) were also independently associated with EI (Table 2).
EI increased progressively with declining kidney function (ANOVA p < 0.001, Tukey post-hoc test), ranging from 0.27 in patients with eGFR ≥60 mL/min/1.73 m² to 0.31 in those on HD (Figure 1).

After adjustment for age, sex, and vascular risk factors, lower eGFR remained independently associated with higher EI. These findings suggest that reduced kidney function may disturb the balance between cerebrospinal fluid (CSF) production and absorption, potentially leading to cerebral ventricular dilation.
Careful neurological and neuroimaging evaluation may be warranted in patients with CKD or on dialysis to detect early signs of CSF circulation disturbance and associated structural brain changes.