Development and performance of a vascular inflammation index for spontaneous isolated superior mesenteric artery...

Spontaneous isolated superior mesenteric artery dissection (SISMAD) is traditionally diagnosed via CT angiography (CTA) structural features, but localized biological inflammation remains poorly characterized. We aimed to characterize the radial spatial gradient of perivascular adipose tissue (PVAT) in SISMAD and evaluate a composite Vascular Inflammation Index (VII) as an auxiliary indicator of local inflammatory activity.

In this retrospective study (2016-2025), 55 patients with SISMAD and 110 symptomatic controls were evaluated. PVAT volume, mean attenuation, and standard deviation (SD) were quantified across cumulative radial shells (0-1 to 0-5 mm) from the SMA wall. A composite VII, integrating volume burden, expansion kinetics, and tissue texture, was developed. Multivariable logistic regression and bootstrap analysis (1000 iterations) assessed independent predictors and incremental diagnostic value.

Participants (mean age, 50.4 years ± 15.9) included SISMAD patients who had higher white blood cell counts than controls (10.7 ± 5.2 vs. 8.7 ± 4.0 × 10⁹/L; P = 0.017). PVAT volume was significantly higher in SISMAD (0-5 mm: 10.1 mm³ ± 5.1 vs. 6.8 mm³ ± 4.0; P < 0.001). SISMAD patients exhibited aggressive radial expansion (expansion ratio: 12.5 vs. 8.6; P = 0.032) and lower 3-mm heterogeneity (22.8 vs. 24.1 HU; P = 0.046), suggesting an edema-induced homogenization effect. The VII achieved an AUC of 0.800 (95% CI 0.723, 0.878) for the identification of SISMAD-associated periarterial involvement and was the independent predictor of SISMAD (OR, 3.23; P < 0.001). Adding VII to the clinical model (Age, Gender, BMI, and WBC) significantly improved performance (AUC, 0.892 vs. 0.857; P = 0.038; increment, 0.035). A seven-day inflammatory plateau was identified post-onset.

Automated radial spatial profiling of PVAT reveals a distinct volumetric and kinetic inflammatory signature in SISMAD. The integrated VII provides a quantitative biological assessment that complements structural CTA diagnosis.