Tuesday, January 15, 2013

190 - Empyema necessitans

*I have always been a fan of medical nomenclature, but iam not sure about this one.
*Medical words usually give away most of the information by their names itself, but this one is tricky.

*Empyema necessitans is a condition where the pus in the thorax (empyema - developed due to some infectious process of lung and pleura) leaks into the soft tissues of the thorax, after burrowing through the parietal pleura. (the name doesn't give away anything, does it?).

*The word empyema implies that the pus is contained in the pleural cavity.

*It may either occur due to the virulence of the organism or may be facilitated by previous thoracic surgery (e.g thoracotomy) or trauma allowing infection to track through.

*It occurs commonly to subcutaneous tissues of the chestwall, but can also spread to involve other sites such as the esophageal, breast, retroperitoneal, peritoneal, pericardial, para vertebral regions.
*The resultant subcutaneous abscess may eventually rupture through the skin.

* Causative organisms are Mycobacterium tuberculosis - thought to be commonest cause, Actinomyces spp - considered second commonest cause,  Blastomycosis spp, Aspergillus spp, Mucormycosis spp.

*Radiographic features : CT chest Best at assessing extent of infection out of the thoracic cavity. will classically show an empyema (often relatively well demarctated collection) with extension through the chest wall into an extra-thoracic compartment. Accompanying rib destruction may be present.

*Differential diagnosis : General imaging differential considerations include malignant pleural based mass - e.g. mesothelioma : different clinical context and will have more solid components, trans-diaphragmatic spread of intra abdominal infection / collection

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