Empyema necessitatis is a collection of inflammatory tissue that usually extends directly from the pleural cavity into the thoracic wall, forming a mass in the extrapleural soft tissues of the chest
1. It is characterized by the extension of suppuration from the pleural space, typically through the thoracic wall, forming subcutaneous abscess. Clinically, patients show symptoms of enlarging, tender, erythematous mass, cough, chest pain and dyspnea
3. The most common site is the anterior chest wall between the midclavicular and anterior axillary line and between the second and sixth intercostal spaces
4. Less commonly, it can involve the bronchus, vertebral column, diaphragm, breast, mediastinum, retroperitoneum, esophagus, pericardium, flank or groin
5. It was first described in 1640 by Baillon, who reported a woman with left sided pulsating tumor associated with pleurisy. The most common etiology is
Mycobacterium tuberculosis and cases of
Actinomycosis species,
Streptococcus pneumonia,
Staphylococcus aureus,
Blastomycosis species, and neoplasms have been reported. Three reports have reviewed cases of empyema necessitatis. In 1940, Sindel
4 reviewed 115 cases.
Mycobacterium tuberculosis was the most common etiology with 84 (73%) cases. In 2004, Freeman et al.
5 reviewed 26 cases from 1966 to 2004 and 13 (50%) cases was caused by
Mycobacterium tuberculosis. Recently, in 2010, Llamas-Velasco et al.
3 reviewed 20 cases from 2004 and
Mycobacterium tuberculosis was less common (7 cases, 35%) than the previous reports but still the most common infectious agent. There were no data concerning the prevalence of chronic kidney disease or patients on dialysis in these reports.
Empyema necessitatis is thought as an unusual complication of empyema with decreasing incidence, while most of its patients were described in the preantibiotic era. However, immunocompromised patients including patients with chronic kidney disease on dialysis are at a higher risk of empyema necessitatis
1,2. Cellular and humoral immunity are both reduced in patients with chronic kidney disease on dialysis and risk of tuberculosis infection is 6.9- to 62.5-fold higher than the general population
6. Additionally, extra pulmonary involvements are more frequent than isolated pulmonary disease in these patients, leading to delayed diagnosis
7.
Mortality is significantly decreasing with antibiotic therapy, from 66% in the preantibiotic era to less than 5% nowadays
3,4. Mortality from recent cases were also associated with reduced immune defence such as old age
8, neoplastic
9, or cystic fibrosis
10. Although there has been no recent case of mortality reported with patients on dialysis, higher mortality is expected.
The differential diagnosis of empyema necessitatis includes neoplasms, Wegener's granulomatosis, sarcoidosis, infective endocarditis and septic embolization
11. CT scan and biopsy are important for accurate diagnosis. CT is helpful in detection and characterization of empyema necessitatis while tissue and fluid for cytological diagnosis and culture can be aspirated by FNAB
12,13.
In summary, empyema necessitatis should be considered in any patient with an enlarging soft tissue mass on the chest wall especially in immunocompromised patients such as patients with chronic renal failure on dialysis, even though history or symptoms of infection are absent. Early diagnosis and proper management can be associated with the best outcome.