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Acute mediastinitis — descending necrotising and post-sternotomy
Acute mediastinitis is a lethal infection of the mediastinum arising from three main sources — a neck or dental infection descending into the mediastinum, cardiac surgery through the sternum, and oesophageal perforation; diagnosis is by CT of neck and chest, and treatment always combines broad antibiotics with early and complete surgical drainage.
Why it matters in the exam
Descending necrotising mediastinitis (DNM) begins with an infection of the teeth, pharynx or tonsils, spreading through the deep neck spaces (mainly the retropharyngeal and "danger" spaces) into the mediastinum. It is a mixed infection — streptococci, anaerobes and Gram-negative bacteria — and its mortality is high. Diagnostic criteria include a severe neck infection, typical CT findings and a clear link between them. CT of the neck and chest together is mandatory, because neck drainage alone is not enough when the infection has descended below the carina. In the Endo classification: type I is confined to the upper mediastinum above the carina; type IIA reaches the lower anterior mediastinum; type IIB also reaches the lower posterior mediastinum. In type I neck drainage usually suffices, and in type II transthoracic drainage (thoracotomy or VATS) is needed in addition to the neck.
Deep sternal wound infection after cardiac surgery occurs in a minority of patients (about 1–2%), usually in the first weeks: fever, purulent wound discharge, unstable sternal movement (a "click") and signs of sepsis. Risk factors: diabetes, obesity, COPD, redo surgery and use of both internal thoracic arteries. The common organism is Staphylococcus aureus (including MRSA), followed by coagulase-negative staphylococci. Treatment: removal of the sternal wires, debridement of necrotic tissue and infected bone, negative pressure wound therapy (NPWT) and delayed closure with a muscle flap (pectoralis major) or omentum, together with prolonged antibiotics. Mediastinitis from oesophageal perforation is treated by the principles of perforation — drainage, closure or diversion and antibiotic cover.
In all types delay in drainage is the main cause of death, so one does not "try antibiotics first".
Key points
- Three sources: neck, cardiac surgery, oesophagus.
- CT of neck and chest.
- Below the carina — transthoracic drainage.
- After cardiac surgery — debridement, NPWT, flap.
- Delay in drainage raises mortality.
Summary table
| Type | Source and picture | Treatment |
|---|---|---|
| Descending necrotising — Endo I | Neck infection, confined above the carina | Broad antibiotics and cervical drainage |
| Descending necrotising — Endo IIA/IIB | Descends to the lower anterior or also posterior mediastinum | Cervical and transthoracic drainage |
| Post-sternotomy | Fever, pus, unstable sternum | Debridement, NPWT, muscle flap or omentum |
| From oesophageal perforation | Chest pain after vomiting or endoscopy | By the principles of perforation |
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Sources
- STS practice guideline series: Antibiotic prophylaxis in cardiac surgery, 2007 — Choice of antibiotic and wound infection prevention
- Endo et al., Jpn J Thorac Cardiovasc Surg, 1999 — Guideline of surgical management based on diffusion of descending necrotizing mediastinitis
- Shields' General Thoracic Surgery, 8th edition (2019) — Acute and chronic mediastinal infection
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.