Abscess
An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends beyond the swelling. Carbuncles and boils are types of abscess that often involve hair follicles, with carbuncles being larger. A cyst is related to an abscess, but it contains a material other than pus, and a cyst has a clearly defined wall.
| Abscess | |
|---|---|
| Other names | Latin: Abscessus |
| Five-day-old inflamed epidermal inclusion cyst. The black spot is a keratin plug which connects with the underlying cyst. | |
| Specialty | General surgery, Infectious disease, dermatology |
| Symptoms | Redness, pain, swelling |
| Usual onset | Rapid |
| Causes | Bacterial infection (often MRSA) |
| Risk factors | Intravenous drug use |
| Diagnostic method | Ultrasound, CT scan |
| Differential diagnosis | Cellulitis, sebaceous cyst, necrotising fasciitis |
| Treatment | Incision and drainage, Antibiotics |
| Frequency | ~1% per year (United States) |
They are usually caused by a bacterial infection. Often many different types of bacteria are involved in a single infection. In many areas of the world, the most common bacteria present is methicillin-resistant Staphylococcus aureus. Rarely, parasites can cause abscesses; this is more common in the developing world. Diagnosis of a skin abscess is usually made based on what it looks like and is confirmed by cutting it open. Ultrasound imaging may be useful in cases in which the diagnosis is not clear. In abscesses around the anus, computer tomography (CT) may be important to look for deeper infection.
Standard treatment for most skin or soft tissue abscesses is cutting it open and drainage. There appears to be some benefit from also using antibiotics. A small amount of evidence supports not packing the cavity that remains with gauze after drainage. Closing this cavity right after draining it rather than leaving it open may speed healing without increasing the risk of the abscess returning. Sucking out the pus with a needle is often not sufficient.
Skin abscesses are common and have become more common in recent years. Risk factors include intravenous drug use, with rates reported as high as 65% among users. In 2005, 3.2 million people went to American emergency departments for abscesses. In Australia, around 13,000 people were hospitalized in 2008 with the condition.