Intra-Abdominal Abscesses

Intra-abdominal abscesses are classified as intraperitoneal, retroperitoneal, or visceral (see table ).

Many intra-abdominal abscesses develop after perforation of a hollow viscus or colonic cancer. Others develop by extension of infection or inflammation resulting from conditions such as appendicitis Appendicitis Appendicitis is acute inflammation of the vermiform appendix, typically resulting in abdominal pain, anorexia, and abdominal tenderness. Diagnosis is clinical, often supplemented by CT or ultrasonography... read more , diverticulitis Colonic Diverticulitis Diverticulitis is inflammation with or without infection of a diverticulum, which can result in phlegmon of the bowel wall, peritonitis, perforation, fistula, or abscess. The primary symptom... read more , Crohn disease Crohn Disease Crohn disease is a chronic transmural inflammatory bowel disease that usually affects the distal ileum and colon but may occur in any part of the gastrointestinal tract. Symptoms include diarrhea... read more , pancreatitis Overview of Pancreatitis Pancreatitis is classified as either acute or chronic. Acute pancreatitis is inflammation that resolves both clinically and histologically. Chronic pancreatitis is characterized by histologic... read more , pelvic inflammatory disease Pelvic Inflammatory Disease (PID) Pelvic inflammatory disease (PID) is a polymicrobial infection of the upper female genital tract: the cervix, uterus, fallopian tubes, and ovaries; abscess may occur. PID may be caused by sexually... read more , or indeed any condition causing generalized peritonitis Peritonitis Abdominal pain is common and often inconsequential. Acute and severe abdominal pain, however, is almost always a symptom of intra-abdominal disease. It may be the sole indicator of the need... read more .

Abdominal surgery, particularly that involving the digestive or biliary tract, is a significant risk factor: The peritoneum may be contaminated during or after surgery by events such as anastomotic leaks. Traumatic abdominal injuries—particularly lacerations and hematomas of the liver, pancreas, spleen, and intestines—may develop abscesses, whether treated operatively or not.

The infecting organisms typically reflect normal bowel flora and are a complex mixture of anaerobic and aerobic bacteria. Most frequent isolates are

Abscesses may form within 1 week of perforation or significant peritonitis, whereas postoperative abscesses may not occur until 2 to 3 weeks after operation and, rarely, not for several months. Although manifestations vary, most abscesses cause fever and abdominal discomfort ranging from minimal to severe (usually near the abscess). Paralytic ileus, either generalized or localized, may develop. Nausea, anorexia, and weight loss are common.

Abscesses in the Douglas cul-de-sac, adjacent to the rectosigmoid junction, may cause diarrhea. Contiguity to the bladder may result in urinary urgency and frequency and, if caused by diverticulitis, may create a colovesical fistula.

Subphrenic abscesses may cause chest symptoms such as nonproductive cough, chest pain, dyspnea, hiccups, and shoulder pain. Rales, rhonchi, or a friction rub may be audible. Dullness to percussion and decreased breath sounds are typical when basilar atelectasis, pneumonia, or pleural effusion occurs.

Generally, there is tenderness over the location of the abscess. Large abscesses may be palpable as a mass.

CT of the abdomen and pelvis with oral contrast is the preferred diagnostic modality for suspected abscess.

Other imaging studies, if done, may show abnormalities; plain abdominal x-rays may reveal extraintestinal gas in the abscess, displacement of adjacent organs, a soft-tissue density representing the abscess, or loss of the psoas muscle shadow. Abscesses near the diaphragm may result in chest x-ray abnormalities such as ipsilateral pleural effusion, elevated or immobile hemidiaphragm, lower lobe infiltrates, and atelectasis.

A complete blood count and blood cultures should be done. Leukocytosis occurs in most patients, and anemia is common.

Occasionally, radionuclide scanning with indium-111–labeled leukocytes may be helpful in identifying intra-abdominal abscesses.

Almost all intra-abdominal abscesses require drainage, either by percutaneous catheters or surgery. Exceptions to drainage include small (< 2 cm) pericolic or periappendiceal abscesses, or abscesses that are draining spontaneously to the skin or into the bowel. Drainage through catheters (placed with CT or ultrasound guidance) may be appropriate given the following conditions:

Antibiotics are not curative but may limit hematogenous spread and should be given before and after intervention. Therapy requires IV antibiotics active against bowel flora.

Patients with community-acquired infection should be characterized as at low or high risk of treatment failure or death based on signs of sepsis or septic shock Symptoms and Signs Sepsis is a clinical syndrome of life-threatening organ dysfunction caused by a dysregulated response to infection. In septic shock, there is critical reduction in tissue perfusion; acute failure... read more , extremes of age, comorbidities, extent of abdominal infection, and risk of resistant bacteria. For community-acquired infection in patients at low risk, recommended regimens include ertapenem as a single medication or metronidazole plus either cefotaxime or ceftriaxone. For community-acquired infection in patients at high risk, recommended regimens include piperacillin/tazobactam, cefepime plus metronidazole, imipenem/cilastatin, or meropenem. Patients previously given antibiotics or those who have hospital-acquired infections should receive antibiotics active against resistant aerobic gram-negative bacilli (eg, Pseudomonas) and anaerobes. (See also the Surgical Infection Society's 2017 revised guidelines on the management of intra-abdominal infection.)

Nutritional support is important, with the enteral route preferred. Parenteral nutrition should begin early if the enteral route is not feasible.

Complicated intra-abdominal abscesses (those extending beyond a single organ into the peritoneal space) have a mortality rate of 10 to 40%. Outcome depends mainly on the presence of sepsis and on the patient’s primary illness or injury and general medical condition rather than on the specific nature and location of the abscess.

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