An abscess is an accumulation of pus, usually caused by a bacterial infection. When bacteria invade healthy tissue, the infection spreads through the area. Some cells die and disintegrate, leaving spaces where fluid and infected cells accumulate. White blood cells, the body's defenders against infection, move into these spaces, and after engulfing bacteria, they die. The dead white blood cells accumulate as pus, a creamy substance that fills the area. As pus collects, healthy tissue is pushed aside. Tissue eventually grows around the abscess and walls it off; this is the body's attempt to prevent the further spread of infection. If an abscess ruptures internally, the infection may spread either inside the body or under the skin surface, depending on the location of the abscess. A bacterial infection may lead to an abscess in several ways. For example, a puncture wound from a dirty needle may force bacteria under the skin. Or bacteria may spread from an infection elsewhere in the body. Also, bacteria that normally live on the body but cause no harm can sometimes cause an abscess. The chances of an abscess forming increase if there is dirt or a foreign body in the infected area; if the area of bacterial invasion has a poor blood supply, as occurs in diabetes; or if the person's immune system is impaired, as occurs in AIDS. Abscesses can develop anywhere in the body, including the lungs, (see page 200 in Chapter 42, Lung Abscess) mouth, (see page 466 in Chapter 94, Tooth Disorders) rectum, (see page 501 in Chapter 103, Disorders of the Anus and Rectum) and muscles. They are fairly common in or just below the skin, especially on the face.
Causes of Soft Tissue Abscess
Abscesses may form below the diaphragm, in the middle of the abdomen, in the pelvis, or behind the abdominal cavity. Abscesses also may form in or around any abdominal organ, such as the kidneys, spleen, pancreas, or liver, or in the prostate gland. Often, abdominal abscesses are caused by injury, infection or perforation of the intestine, or infection of another abdominal organ. An abscess below the diaphragm may form when infected fluid, for example, from a ruptured appendix, is moved upward by the pressure of abdominal organs and by the suction created when the diaphragm moves during breathing. Symptoms may include a cough, painful breathing, and pain in one shoulder--an example of referred pain that occurs because the shoulder and the diaphragm share the same nerves and the brain incorrectly interprets the source of the pain. Abscesses in the midabdomen may result from a ruptured appendix, a perforated large intestine, inflammatory bowel disease, or diverticular disease. The abdomen is usually painful in the area of the abscess. Pelvic abscesses result from the same disorders that cause abscesses in the midabdomen and from gynecologic infections. Symptoms may include abdominal pain, diarrhea from intestinal irritation, and an urgent or frequent need to urinate caused by bladder irritation. Abscesses behind the abdominal cavity (called retroperitoneal abscesses) lie behind the peritoneum, the membrane that lines the abdominal cavity and organs. The causes, which are similar to those of other abscesses in the abdomen, include inflammation of the appendix (appendicitis) and of the pancreas (pancreatitis). Pain, usually in the lower back, worsens when the person moves the leg at the hip. Abscesses in the kidneys are caused either by bacteria from an infection traveling to the kidneys through the bloodstream or by a urinary tract infection traveling to the kidney and then spreading to the kidney tissue. Abscesses on the surface of the kidneys (perinephric abscesses) are nearly always caused by the rupture of an abscess inside the kidney, which spreads the infection to the surface and the surrounding tissue. Symptoms of a kidney abscess include a fever, chills, and pain in the lower back. Urination may be painful, and sometimes the urine is bloody. Abscesses in the spleen are caused by an infection traveling through the bloodstream to the spleen, by an injury to the spleen, or by the spread of an infection from a nearby abscess, such as one below the diaphragm. Pain may occur in the left side of the abdomen, the back, or the left shoulder. Abscesses inside the pancreas typically form after an attack of acute pancreatitis. Symptoms such as fever, abdominal pain, nausea, and vomiting often begin a week or more after a person recovers from pancreatitis. Liver abscesses may be caused by bacteria or by amebas (single-celled parasites). Amebas from an intestinal infection reach the liver through the lymphatic vessels. Bacteria can reach the liver from an infected gallbladder; a penetrating or blunt wound; an infection in the abdomen, such as a nearby abscess; or an infection carried by the bloodstream from elsewhere in the body. Symptoms of liver abscesses include loss of appetite, nausea, and a fever. A person may or may not have abdominal pain. Prostate abscesses usually result from a urinary tract infection that leads to a prostate gland infection (prostatitis). These abscesses most commonly occur in men between ages 40 and 60. Typically, a man with a prostate abscess experiences painful, frequent, or difficult urination. Less commonly, he feels internal pain at the base of the penis and notices pus or blood in his urine. Head and Neck Abscesses Abscesses commonly develop in the head and neck, particularly behind the throat and in the salivary glands of the cheeks (parotid glands). Abscesses can also develop in the brain. (see page 377 in Chapter 78, Infections of the Brain and Spinal Cord) Abscesses behind and to the side of the throat (pharyngomaxillary abscesses) usually result from throat infections, including infections of the tonsils or adenoids. (see page 1018 in Chapter 214, Throat Disorders) Children are more likely than adults to develop a throat abscess. (see page 1265 in Chapter 259, Bacterial Infections) An abscess can also form within a lymph node located beside the throat (a parapharyngeal abscess). (see page 1019 in Chapter 214, Throat Disorders) Less commonly, these abscesses come from a nearby infection, such as a tooth abscess or a salivary gland infection. Along with having a fever and sore throat, the person feels ill. Opening the mouth may be difficult. The infection may spread, causing neck swelling. If the abscess damages the carotid arteries in the neck, clotting or massive bleeding can result. An abscess also may form at the outlet of one of the parotid glands. The abscess is usually caused by an infection spreading from the mouth. This type of abscess typically occurs in elderly or chronically ill people who have a dry mouth resulting from a low fluid intake or from certain drugs, such as antihistamines. Symptoms include pain and swelling in one cheek, fever, and chills that begin suddenly. Muscle Abscesses Abscesses occasionally form deep in muscles. These abscesses may be caused by bacteria spreading from a nearby infection in a bone or other tissue or spreading through the bloodstream from a distant part of the body. Pyomyositis is a disorder in which muscle becomes infected by pus-producing bacteria that often cause abscesses to form. Pyomyositis is more common among people in the tropics and occurs in people with impaired immune systems. The muscles most commonly affected are those in the thighs, buttocks, and upper arms and those around the shoulders. Symptoms include cramping pain followed by swelling, mild fever, and increasing discomfort, especially when the infected muscle is moved. Hand Abscesses Abscesses in the hands are fairly common and usually result from injury. An abscess in the soft pad at the tip of a finger nearly always results from a minor injury, such as a splinter or needle prick. Severe pain, warmth, and redness develop over the abscess, often with swelling of nearby lymph nodes in the arm. Infection of the bone underneath the abscess may cause more pain. Abscesses may occur around the tendons that run along the inside of the fingers. This type of abscess is caused by an injury that penetrates one of the creases on the palm side of a finger. Infection and pus form around the tendon and rapidly destroy tissue. The gliding mechanism of the tendon becomes damaged, so the finger can barely move. Symptoms include swelling and inflammation of the finger, tenderness over the tendon sheath, and extreme pain when trying to move the finger. Swollen lymph nodes near the abscess and fever are common.
Signs and Symptoms of Soft Tissue Abscess
Where an abscess is located and whether it interferes with the function of an organ or a nerve determine its symptoms. Symptoms can include pain, tenderness, heat, swelling, redness, and possibly a fever. An abscess that forms just under the skin usually appears as a visible bump. When an abscess is about to rupture, it develops a whitish center as the overlying skin grows thinner. An abscess deep inside the body often grows quite large before it causes symptoms. Unnoticed, a deep abscess is likely to spread infection throughout the body. Doctors can easily recognize an abscess on or just beneath the skin but often miss a deep abscess.
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Medical Content Last Updated on 07/12/2008
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