Infectious Mediastinitis in a Spanish Tertiary Referral Hospital: An 11-Year Retrospective Cohort Study with Etiology-Specific Analysis and a Descending Necrotizing Mediastinitis Subgroup

Background/Objectives: Infectious mediastinitis is rare, life-threatening, and etiologically heterogeneous. We characterized its contemporary spectrum, temporal patterns, and descending necrotizing mediastinitis (DNM) in a Spanish tertiary referral hospital. Methods: We retrospectively analyzed 66 clinically validated mediastinitis cases managed at Hospital Universitario Central de Asturias from 2014 to 2024. Etiology, microbiology, treatment, hospital stay, and survival to hospital discharge were assessed. Prespecified periods (2014–2018 vs. 2019–2024) were compared using Fisher’s exact and Mann–Whitney U tests. Results: Post-surgical infection was the leading etiology (31/66, 47.0%), followed by DNM (16/66, 24.2%; 9 odontogenic), esophageal perforation (13/66, 19.7%), and other causes (6/66, 9.1%). Crude annual case frequency was stable (6.2 vs. 5.8 cases/year). Cultures yielded growth in 56/66 cases (84.8%); microbiology differed by source, with staphylococci and Enterobacterales predominating after surgery and oral streptococci and anaerobes in DNM. Surgery was performed in 55/66 cases (83.3%). Survival to hospital discharge was 84.8% overall (93.8% in DNM) and did not differ between periods (80.6% vs. 88.6%; p = 0.496). Surgical treatment (93.5% vs. 74.3%; p = 0.049) and culture positivity (96.8% vs. 74.3%; p = 0.015) were less frequent in the later period; these exploratory findings may partly reflect the COVID-19 pandemic. Conclusions: Mediastinitis remained uncommon but resource-intensive. Etiology-specific microbiology supports source-adapted multidisciplinary management and prospective standardized data collection.