Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
- central core comprised of necrotic inflammatory cells and local tissue
- peripheral halo of viable neutrophils
- surrounded by a 'capsule' with dilated blood vessels and proliferation of fibroblasts
Abscesses are akin to empyemas as both are defined inflammatory collections. The difference is that abscesses occur in the parenchyma of the affected organ while empyemas arise in a pre-existing cavity such as the pleural space.
The presentation of an abscess is varied depending on the location and its infiltration of and mass effect on local structures. Systemically, patients with abscesses can present with a swinging pyrexia and raised inflammatory markers, which are resistant to antimicrobial therapy. Pain is a common accompanying symptom.
Abscesses can be caused by bacteria, parasites or fungi.
Essentially any tissue in the body can play host to abscesses. Please refer to individual articles for further details:
- Bezold abscess
- breast abscess
- Brodie abscess
- cerebral abscess
- liver abscess
- pulmonary abscess
- splenic abscess
- subcutaneous abscess
A key radiographic feature of an abscess is that it contains a central zone of necrotic inflammatory material encapsulated by a discernible wall. This can have varying appearances depending on the tissue or organ within which the abscess is situated.
- relative low attenuation central necrotic component
- defined fibrous capsule which can be irregular and thick when compared to the thin smooth wall of a simple cyst
- capsular ring enhancement with contrast which can be difficult to appreciate when the abscess is contained in a vascular structure like the liver where there is concurrent parenchymal enhancement
- surrounding inflammatory changes (i.e. peritoneal fat stranding)
- mass effect with effacement of adjacent structures
The presence of an abscess in patients presenting with sepsis can be delineated by a Indium (In-111) labelled white cell scan, often in the setting of suspected abdominopelvic sepsis. Tracer accumulates in the region of the abscess, such as the right iliac fossa in an appendiceal abscess.
As abscesses usually have a thick wall with poor vascularity, it can take time for In-111 to be taken up and delayed 48 hours images are sometimes required. The sensitivity of this test is not thought to be affected by the use of concomitant antibiotics or steroids.
Treatment and prognosis
Abscesses can either be treated medically or with percutaneous or surgical drainage. The mainstay of medical treatment is antimicrobial drugs. As abscesses have poor vascularity, often high dose oral or parenteral treatment is used. Percutaneous drainage can be performed under ultrasound or CT guidance for abscesses within the thoracic or peritoneal cavity. Some abscesses may require open incision and drainage. The choice of treatment is guided by the size, accessibility, and clinical severity of sepsis in each case.
History and etymology
The word 'abscess' derives from the Greek work 'aposteme' (άπό-ίστημι, 'a throwing off (of bad humours)'). The word first appeared in 1543 in a translation of a surgery text: "Aposteme - In latyne it is called abscissus" 3.
- 1. Kumar V, Abbas AK, Fausto N et-al. Robbins and Cotran pathologic basis of disease. W B Saunders Co. (2005) ISBN:0721601871. Read it at Google Books - Find it at Amazon
- 2. Krige, J E J; Beckingham, I J. ABC of diseases of liver, pancreas, and biliary system: Liver abscesses and hydatid disease BMJ. 322 (7285): 537. doi:10.1136/bmj.322.7285.537 -
- 3. Skinner HA. Origin of Medical Terms. Hafner Publishing Co Ltd. ISBN:0028523903. Read it at Google Books - Find it at Amazon