Distinct Etiological and Clinical Patterns of Acute Mesenteric Ischemia at High Altitude: A Retrospective Comparative Study

Chen, Chen, Yang, Li, Xu, Fan, Xu, Zhijuan Liu, and Dong Wu. Distinct etiological and clinical patterns of acute mesenteric ischemia at high altitude: a retrospective comparative study. High Alt Med Biol. 00:00–00, 2026. Background: Acute mesenteric ischemia (AMI) is a life-threatening abdominal emergency, yet evidence regarding its etiology and clinical outcomes in high-altitude populations remains limited. This study aimed to compare the etiology, clinical characteristics, and outcomes of AMI between high- and low-altitude populations in China. Methods: We conducted a retrospective comparative study at two tertiary referral centers in China: People’s Hospital of the Xizang Autonomous Region (PHOXAR; 3,700 m) and Peking Union Medical College Hospital (PUMCH; <100 m). Mesenteric venous thrombosis (MVT) comparisons were restricted to the overlapping period of 2020–2024. Results: Among 186 patients in the high-altitude cohort and 549 in the low-altitude cohort, MVT was more frequent at high altitude (84.9% vs. 61.2%, p < 0.001). 158 high-altitude and 120 low-altitude patients with MVT were compared. Cirrhosis-related (29.1% vs. 11.7%) and erythrocytosis-related MVT (27.2% vs. 1.7%) were more common in the high-altitude cohort, whereas autoimmune disease-related MVT (0.6% vs. 11.7%) and thrombophilia (0 vs. 16.7%) were more frequent in the low-altitude cohort. High-altitude patients had higher hemoglobin/hematocrit, bilirubin, and fibrinogen levels and a higher mean onset-to-admission time (95.4 vs. 30.2 days). They underwent surgery less frequently (29.7% vs. 80.0%, p < 0.001) and had higher in-hospital mortality (26.6% vs. 11.7%, p = 0.004). Mortality was not significantly different among patients admitted within 2 days (31.6% vs. 8.3%, p = 0.111) but remained higher among those admitted after 2 days (25.9% vs. 12.5%, p = 0.012). Male sex, older age, alcohol consumption, smoking, and higher hematocrit, bilirubin, and fibrinogen were independently associated with the high-altitude MVT phenotype. Conclusions: AMI in the high-altitude population was characterized by a marked predominance of MVT, with distinct etiological and clinical profiles and poorer outcomes. These findings highlight the importance of early recognition, timely referral, and improved access to appropriate treatment for AMI in high-altitude settings.