Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Abdominal Abscesses


Parswa Ansari

, MD, Hofstra Northwell-Lenox Hill Hospital, New York

Reviewed/Revised Apr 2023
Topic Resources

An abscess is a pocket of pus, usually caused by a bacterial infection.

  • Most people have constant abdominal pain and a fever.

  • Computed tomography or another imaging test can distinguish an abscess from other problems.

  • Treatment involves draining pus from the abscess and taking antibiotics.

Abdominal 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. Untreated abscesses can grow and damage nearby blood vessels and organs.

The Digestive System

The Digestive System

Causes of Abdominal Abscesses

Symptoms of Abdominal Abscesses

Specific symptoms of abdominal abscesses depend on the location of the abscess, but most people have constant discomfort or pain, feel generally sick (malaise), and often have a fever. Other symptoms include nausea, loss of appetite, and weight loss.

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, chest pain, and pain in one shoulder. In this instance, the pain felt in one shoulder is an example of referred pain (pain felt in one area of the body that does not accurately represent where the problem is). Referred pain occurs because the shoulder and the diaphragm share the same nerves, and the brain incorrectly interprets the source of the pain (see figure ).

An abscess in the lower abdomen may track down into the thigh or the area around the rectum (called the perirectal fossa).

Pelvic abscesses can result from the same disorders that cause abscesses in the mid-abdomen or from gynecologic infections. Symptoms may include abdominal pain, diarrhea caused by 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 abscesses in the abdomen, include inflammation and infection of the appendix (appendicitis Appendicitis Appendicitis is inflammation and infection of the appendix. Often a blockage inside the appendix causes the appendix to become inflamed and infected. Abdominal pain, nausea, and fever are common... read more ), the pancreas (pancreatitis Overview of Pancreatitis Pancreatitis is inflammation of the pancreas. The pancreas is a leaf-shaped organ about 5 inches (about 13 centimeters) long. It is surrounded by the lower edge of the stomach and the first... read more ), and the kidneys (the kidneys are located behind the abdominal cavity). Pain, usually in the lower back, worsens when the person moves the leg at the hip.

Abscesses of the pancreas, although rare, typically form after an attack of acute pancreatitis Acute Pancreatitis Acute pancreatitis is sudden inflammation of the pancreas that may be mild or life threatening but usually subsides. Gallstones and alcohol abuse are the main causes of acute pancreatitis. Severe... read more . 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, microscopic parasites). 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. Amebas Amebiasis Amebiasis is an infection of the large intestine and sometimes the liver and other organs that is caused by the single-celled protozoan parasite Entamoeba histolytica, an ameba. The amebas... read more from an intestinal infection reach the liver through the blood vessels. Symptoms of liver abscesses include loss of appetite, nausea, and a fever. A person may or may not have abdominal pain.

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.

Diagnosis of Abdominal Abscesses

  • Imaging tests

  • Needle aspiration

Doctors can easily misdiagnose an abscess because the first symptoms it causes are usually vague and mild and may be mistaken for less serious problems that are more common.

To make a definitive diagnosis and treat the abscess, doctors sometimes insert a needle through the skin to draw a sample of pus from the abscess (needle aspiration) and place a drain. To guide the placement of the needle, doctors use CT or ultrasound scanning. The sample of fluid is then examined in a laboratory to identify the infecting organism so that the most effective antibiotic can be selected.

Occasionally, radionuclide scanning Radionuclide Scanning Radionuclide scanning is a type of medical imaging that produces images by detecting radiation after a radioactive material is administered. During a radionuclide scan, a small amount of a radionuclide... read more is done to help identify abscesses. For scanning, a radionuclide is used to label a substance that accumulates in a specific part of the body. Different substances are used depending on which part of the body is to be evaluated.

Treatment of Abdominal Abscesses

  • Drainage of pus

  • Antibiotics

Almost all abdominal abscesses need to be drained of pus, either by surgery or by a needle and a small flexible tube (catheter). To guide the placement of the needle and catheter, a doctor uses CT or ultrasound scanning. Once the doctor is sure the needle and catheter have reached the abscess, the needle is taken out but the catheter is left in place. The pus drains out through the catheter, usually over several days to weeks.

Antibiotics are usually used in addition to drainage to prevent the infection from spreading and to help completely eliminate the infection. Laboratory analysis of the pus identifies the infecting organism so that the most effective antibiotic can be selected. It is uncommon for antibiotics to cure an abscess without drainage.

If the abscess cannot be reached safely by the needle and catheter, surgical drainage may be necessary. Once the abscess has been drained, the source of the infection is also surgically treated. For example, if the abscess is caused by a perforation (hole) in the colon, doctors usually remove that part of the colon.

Prognosis for Abdominal Abscesses

Abdominal abscesses can cause death in about 10 to 40% of people. What caused the abscess and a person's general medical condition affect the prognosis more than the specific nature and location of the abscess. People who develop sepsis Sepsis and Septic Shock Sepsis is a serious bodywide response to bacteremia or another infection plus malfunction or failure of an essential system in the body. Septic shock is life-threatening low blood pressure ... read more have a worse prognosis.

quiz link

Test your knowledge

Take a Quiz!