Acute mediastinitis is a life-threatening infection; mediastinal masses are characterized by anatomic compartment and patient age.
Also known as: mediastinitis, mediastinal mass, anterior mediastinal mass, descending necrotizing mediastinitis, post-sternotomy mediastinitis
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Question 1PulmonaryMedium
A 55-year-old man with a remote history of pulmonary histoplasmosis 10 years ago presents with 3 months of progressive dyspnea, dysphagia to solids, facial swelling, and distended neck veins. Exam shows facial plethora, dilated chest wall venous collaterals, and bilateral upper extremity edema. Chest CT reveals a calcified, infiltrative mediastinal mass encasing the superior vena cava and right mainstem bronchus with extensive mediastinal calcifications. Bronchoscopy with biopsy is nondiagnostic for malignancy. Which of the following is the most likely complication of his prior infection?
- AChronic pulmonary aspergilloma of a residual cavity
- BFibrosing mediastinitis from prior histoplasma infection
- CReactivation chronic cavitary pulmonary histoplasmosis
- DHistoplasma pericarditis with constrictive physiology
Reveal answer & full explanation
Correct answer: B — Fibrosing mediastinitis from prior histoplasma infection
- AChronic pulmonary aspergilloma of a residual cavity
- BFibrosing mediastinitis from prior histoplasma infection✓
- CReactivation chronic cavitary pulmonary histoplasmosis
- DHistoplasma pericarditis with constrictive physiology
Why Fibrosing mediastinitis from prior histoplasma infection is correct
- Fibrosing (sclerosing) mediastinitis is the most feared late complication of pulmonary histoplasmosis
- The mechanism is dysregulated fibroblast proliferation triggered by residual fungal antigens, producing an exuberant fibrotic host response
- The result is a calcified mediastinal mass that compresses central airways, great vessels, and the esophagus
- Presentation is typically 5–15 years after primary infection with superior vena cava (SVC) syndrome, pulmonary hypertension, or central airway obstruction
- Calcified mediastinal lymphadenopathy with vascular encasement on CT is the classic imaging finding
Why the others are wrong
- A) Chronic pulmonary aspergilloma of a residual cavity — aspergilloma colonizes prior histoplasma cavities but produces hemoptysis with a fungus ball within a cavity, not a calcified infiltrative mediastinal mass
- C) Reactivation chronic cavitary pulmonary histoplasmosis — reactivation cavitation occurs in patients with underlying emphysema and presents with upper-lobe cavities and constitutional symptoms, not SVC obstruction
- D) Histoplasma pericarditis with constrictive physiology — constriction elevates jugular venous pressure but produces lower extremity edema, hepatomegaly, and ascites; it does not encase the SVC or explain facial plethora, bilateral upper extremity edema, and chest wall venous collaterals
Additional high-yield points
- Treatment of fibrosing mediastinitis is largely supportive with vascular or airway stenting
- Antifungals and corticosteroids have not been shown to reverse established fibrosis
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Risk factors
- Mediastinitis: recent cardiothoracic surgery, esophageal instrumentation or perforation, severe odontogenic or retropharyngeal infection, diabetes, obesity, immunosuppression
- Anterior masses: 'Four Ts' — Thymoma, Teratoma/germ cell tumor, Thyroid (substernal goiter), Terrible lymphoma
- Middle masses: lymphadenopathy (sarcoid, lymphoma, metastatic, infectious), bronchogenic cysts, vascular anomalies
- Posterior masses: neurogenic tumors (schwannoma, neurofibroma, ganglioneuroma in children), spinal lesions, extramedullary hematopoiesis
Pathophysiology
Acute bacterial mediastinitis spreads rapidly along fascial planes due to negative intrathoracic pressure and continuous tissue communication. Common pathogens after sternotomy: Staphylococcus aureus (including MRSA), coagulase-negative staphylococci, gram-negatives. Descending necrotizing mediastinitis is typically polymicrobial with oral anaerobes (Bacteroides, Fusobacterium, Peptostreptococcus) and Streptococcus species. Mediastinal masses cause local compression (SVC syndrome, tracheal compression, dysphagia) and systemic effects (paraneoplastic syndromes).
Clinical presentation
Symptoms
- Mediastinitis: fever, chest pain, tachycardia, sternal instability or drainage after sternotomy, neck swelling and odynophagia in descending forms
- Mediastinal mass: many incidental; symptoms from compression — cough, dyspnea, dysphagia, hoarseness (recurrent laryngeal nerve), SVC syndrome (facial plethora, distended neck veins, upper extremity edema)
- Constitutional symptoms (B symptoms) suggest lymphoma or germ cell tumor
- Myasthenic symptoms (ptosis, diplopia, proximal weakness, fatigability) point to thymoma
Signs / physical exam
- Mediastinitis: wound erythema/dehiscence, purulent drainage, crepitus (subcutaneous emphysema)
- Hamman sign: mediastinal crunch synchronous with the heartbeat (pneumomediastinum)
- Pemberton sign: facial plethora when arms raised overhead (substernal goiter or SVC syndrome)
Differential diagnosis
- Acute MI / aortic dissection — Chest pain with hemodynamic instability; ECG and CTA differentiate
- Pulmonary embolism — Pleuritic pain, hypoxia; CTPA diagnostic
- Esophageal perforation (Boerhaave) — Severe chest pain after forceful emesis, subcutaneous emphysema, pneumomediastinum on CT, left pleural effusion with low pH and high amylase
- Thymoma — Anterior mediastinal mass in adult 40-60 y; associated with myasthenia gravis (~30-40%), pure red cell aplasia, hypogammaglobulinemia
- Germ cell tumor — Young men 20-40 y; elevated AFP (yolk sac/nonseminoma), beta-hCG (choriocarcinoma); seminomas usually normal AFP
- Lymphoma — B symptoms (fever, night sweats, weight loss), bulky bilateral lymphadenopathy, biopsy for histology
- Substernal thyroid — Continuity with cervical thyroid on imaging, iodine uptake on scintigraphy
- Neurogenic tumor — Posterior mediastinal mass, often pediatric or young adult; CT shows widening of intervertebral foramen
Diagnostic workup
Diagnostic criteria
Post-sternotomy mediastinitis (CDC criteria): organism isolated from culture of mediastinal tissue/fluid OR evidence of mediastinitis on imaging/exploration PLUS fever, chest pain, or sternal instability with purulent drainage or positive culture.
Labs
- CBC, CMP, lactate, blood cultures for suspected mediastinitis
- Procalcitonin and inflammatory markers (CRP, ESR) for trending
- Tumor markers for anterior mass in young men: AFP, beta-hCG, LDH
- Anti-AChR and anti-MuSK antibodies if myasthenia gravis suspected
- TSH for suspected substernal thyroid
Imaging
- Contrast-enhanced CT chest is the cornerstone imaging study for both mediastinitis and mediastinal masses
- CT signs of mediastinitis: fluid collections, pneumomediastinum, fat stranding, mediastinal widening; in post-sternotomy patients, sternal dehiscence and retrosternal collections
- Water-soluble contrast esophagogram if esophageal perforation suspected, followed by barium if initial study negative
- MRI for posterior masses to assess spinal canal involvement
- PET/CT and tissue diagnosis (CT-guided core biopsy, EBUS, mediastinoscopy, or VATS) for mass characterization
Treatment
First-line
- Acute mediastinitis: hemodynamic resuscitation, broad-spectrum IV antibiotics initiated within 1 hour after blood cultures
- Empiric coverage: vancomycin (MRSA) PLUS piperacillin-tazobactam or cefepime/metronidazole (gram-negatives and anaerobes); add antifungal if immunocompromised or prolonged ICU stay
- Urgent surgical debridement and drainage; sternal rewiring with omental or muscle flap reconstruction for sternal wound infections
- Esophageal perforation: NPO, NG decompression, broad-spectrum antibiotics, antifungals (Candida coverage), early surgical or endoscopic repair (stent, primary repair, esophagectomy in late presentations)
Thymoma
- Surgical resection (thymectomy) for stage I-II disease
- Adjuvant radiation for invasive disease; chemotherapy (cisplatin-based) for unresectable or recurrent
- Manage associated myasthenia gravis with pyridostigmine, prednisone, and immunosuppressants
Germ cell tumor
- Seminoma: cisplatin-based chemotherapy (BEP — bleomycin/etoposide/cisplatin) or radiation; surgery for residual mass
- Nonseminomatous: BEP followed by resection of residual disease
Lymphoma
- Tissue diagnosis essential before treatment
- Hodgkin: ABVD or escalated BEACOPP per stage
- Diffuse large B-cell: R-CHOP
- Primary mediastinal B-cell: DA-EPOCH-R
Complications
- Sepsis, septic shock, multi-organ failure
- SVC syndrome, tracheal compression, airway compromise — anesthesia risk in anterior masses
- Empyema, pleural effusion, pericardial effusion/tamponade
- Mediastinal fistula, recurrent infection, prolonged ICU stay
- Post-thymectomy myasthenic crisis
PANCE pearls
- Pre-induction airway and cardiac assessment is mandatory for large anterior mediastinal masses — supine positioning can precipitate fatal airway collapse.
- Hamman crunch with subcutaneous emphysema after vomiting = Boerhaave until proven otherwise.
- AFP elevation is incompatible with pure seminoma — the mass contains a non-seminomatous element.
- Always check anti-AChR antibodies in adults with anterior mediastinal mass to detect occult myasthenia gravis.
- Descending necrotizing mediastinitis arises from odontogenic or retropharyngeal infection — early CT neck/chest and aggressive surgical drainage save lives.
References
- CHEST 2016 — Carter BW et al. ITMIG Classification of Mediastinal Compartments and Multidisciplinary Approach to Mediastinal Masses. RadioGraphics 2017;37:413-436
- STS — El Oakley RM, Wright JE. Postoperative Mediastinitis: Classification and Management. Ann Thorac Surg 1996;61:1030-1036 (reference classification)
- IDSA — Infectious Diseases Society of America Guidelines: Surgical Site Infections (2017 update)