To explore the potential risk factors for the progression of non-traumatic subdural effusion (NTSE) to chronic subdural hematoma (CSDH).

NTSE patients who met the criteria and were screened at Xiaolan Clinical Institute of Shantou University Medical College (Xiaolan People's Hospital of Zhongshan City) and Luhe County People's Hospital of Shanwei City from June 2021 to March 2025 were selected as the study subjects. Patients were divided into hematoma group and effusion group based on whether they progressed to hematoma. Clinical data of the two groups were compared, and multiple Logistic regression analysis was used to screen for independent risk factors for NTSE progression to CSDH. Based on the regression model results, receiver operating characteristic (ROC) curves were plotted to evaluate the diagnostic efficacy of the model.

This study ultimately included 82 NTSE patients, including 31 cases (37.8%) in hematoma group and 51 cases (62.2%) in effusion group. Compared with the effusion group, the hematoma group had higher proportion of patients taking anticoagulant/antiplatelet medications, higher CT attenuation values of subdural effusion, and greater effusion asymmetry, larger maximum outer diameter of the lateral ventricular body, lower lateral ventricular body index and lateral ventricular body width index, with statistical significance (P<0.05). Multivariate Logistic regression analysis showed that increased CT attenuation values of subdural effusion and asymmetric fluid accumulation were independent risk factors for the progression of NTSE to CSDH. ROC curve analysis showed that the overall area under the curve (AUC) of the model was 0.866 (95%CI: 0.805-0.967), the AUC of CT attenuation values of subdural effusion was 0.828 (95%CI: 0.713-0.944), and the AUC of effusion symmetry was 0.772 (95%CI: 0.649-0.895). The predictive performance of the overall model and the CT value of fluid accumulation is higher than that of fluid symmetry.

High CT attenuation values of subdural effusion and effusion asymmetry were independent risk factors for the progression of NTSE to CSDH. The Logistic regression prediction model based on risk factors and CT attenuation values of subdural effusion have shown good predictive performance, which can effectively quantify the risk probability of NTSE progressing to CSDH.