What is "phlegmon"

Phlegmon \Phleg"mon\, n. [L. phlegmone, phlegmon, inflammation beneath the skin, Gr. ?, fr. ? to burn: cf. F. phlegmon.] (Med.) Purulent inflammation of the cellular or areolar tissue.

n. A solid mass formed by inflamed connective tissue, such as forms around an appendix in appendicitis.

Phlegmon is a spreading diffuse inflammatory process with formation of suppurative/purulent exudate or pus. This is the result of acute purulent inflammation which may be related to bacterial infection, however the term 'phlegmon' mostly refers to a walled-off inflammatory mass without bacterial infection, one that may be palpable on physical examination.

An example would be phlegmon of diverticulitis. In this case a patient would present to the emergency department with left lower-quadrant abdominal tenderness, and the diagnosis of sigmoid diverticulitis would be high on the differential diagnosis, yet the best test to confirm it would be CT scan.

Another example, phlegmon affecting the spine, is known as spondylodiscitis and is associated with endplate destruction and loss of disc height. In adults, the bone marrow is affected first, while in children, the disease starts in the disc itself and spreads rapidly to the adjacent vertebral bodies. Phlegmon in the spine can be a diffuse enhancement, or localized abscess, (peripheral enhancement) in the epidural, subligamentous or paraspinous spaces. Under MRI examination, phlegmon will show dark with T1, and high signal (bright) with T2.