Objectives Descending necrotizing mediastinitis (DNM) is a poor prognosis disease. This study aims to examine the patient background and treatment of DNM and to identify more effective treatments for DNM.

Methods The patient background and treatment of 11 patients who underwent surgery for DNM between November 2010 and June 2021 were studied. The patients were divided into six patients who underwent continuous saline irrigation (group I) and five patients who did not (group N). The differences in the drainage duration and length of hospital stay between the two groups were retrospectively investigated.

Results Eleven patients were treated for DNM: six male and five female, with a median age of 61 years (35–79). Comorbidities included diabetes mellitus in three cases; one patient was administered steroids. The pathways of occurrence were anterior tracheal gap/vascular visceral gap/posterior visceral gap in group I (2/1/2) and group N (0/2/4). Progression was I/IIA/IIB according to Endo's classification in group I (1/1/4) and group N (3/1/1). The mean duration of irrigation was 9.0 ± 3.7 days, and the drainage duration in group I was 17.5 ± 8.2 days, which was significantly shorter than 31 ± 13.6 days in group N (p < 0.048). The hospital stays in group I was 29.3 ± 8.4 days, which was significantly shorter than that in group N (68 ± 27.1 days; p < 0.015).