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Practice Guidelines

Evaluation of Complicated Intra-Abdominal Infections: Updated Guidelines From the IDSA

Giulia Gargano, MD
Michelle Nelson, MD

American Family Physician. 2026;114(2):204-206.

Author Disclosure: No relevant financial relationships.

This clinical content conforms to AAFP criteria for CME.

KEY POINTS FOR PRACTICE

• Obtaining blood cultures is recommended for suspected intra-abdominal infection when patients present with elevated temperature as well as hypotension, tachypnea, or delirium, or when there is concern for antibioticresistant organisms.
• Ultrasonography is the preferred imaging modality for intra-abdominal infections in children.
• In pregnant patients, ultrasonography and MRI are the preferred primary imaging modalities depending on availability and clinical context.
• The APACHE II score should be used within 24 hours of hospitalization or intensive care unit admission to estimate 30-day or in-hospital mortality risk for adults with complicated intra-abdominal infections.
From the AFP Editors

Acomplicated intra-abdominal infection extends beyond the origin into the peritoneal space or extraperitoneal abdomen to cause peritonitis with or without abscess formation. This includes acute appendicitis, acute cholecystitis, acute cholangitis, acute diverticulitis, abdominal abscess, secondary bowel perforation, and acute necrotizing pancreatitis. The Infectious Diseases Society of America (IDSA) updated its guidelines on complicated intra-abdominal infections focusing on imaging and microbiologic evaluation. All recommendations are conditional (ie, although they apply to most people, there are many exceptions, and shared decision-making is important) and are based on very low- to moderate-quality evidence.

CULTURES

Blood and intra-abdominal fluid cultures should be obtained when results may influence antimicrobial therapy.

Blood Cultures

The IDSA suggests obtaining blood cultures in patients with suspected intra-abdominal infection when antibiotic-resistant infection is suspected or when elevated temperature is accompanied by hypotension, tachypnea, or delirium. Risk factors for resistant organisms include high local resistance to common empiric regimens, a personal history of resistant infection or colonization, antibiotic use within the past 90 days, older age, immunocompromised status, significant comorbidities, and health care–associated infection.

Blood cultures are not routinely recommended for immunocompetent adults and children who do not meet these criteria.

Intra-Abdominal Fluid Cultures

For immunocompetent patients, the IDSA suggests obtaining intra-abdominal fluid cultures only during a planned source-control procedure for complicated intra-abdominal infections. Fluid inoculation is the preferred collection method. Cultures are not routinely recommended during surgery for uncomplicated appendicitis, although they may be useful in immunocompromised patients or when complicated disease is suspected during surgery.

IMAGING

Ultrasonography is preferred in children to avoid radiation exposure and need for sedation. In pregnant patients, ultrasonography and magnetic resonance imaging (MRI) are the preferred imaging modalities, with selection based on availability and clinical scenario. In nonpregnant adults, the suggested imaging modality varies by the suspected infection (Table 1).

TABLE 1. Initial Imaging for Patients With Intra-Abdominal Infections

Condition Children Nonpregnant adults Pregnant adults
Appendicitis Ultrasonography CT with IV contrast preferred over noncontrast CT Ultrasonography or MRI
Cholangitis Ultrasonography Ultrasonography Ultrasonography or MRI
Cholecystitis Ultrasonography Ultrasonography Ultrasonography or MRI
Diverticulitis NA CT with IV contrast preferred over noncontrast CT Ultrasonography or MRI
Intra-abdominal abscess Ultrasonography CT with IV contrast preferred over noncontrast CT Ultrasonography or MRI

CT = computed tomography; IV = intravenous; MRI = magnetic resonance imaging; NA = not applicable.

GIULIA GARGANO, MD, is a PGY-2 at Henry Ford Health Providence Family Medicine Residency, Southfield, Michigan.

MICHELLE NELSON, MD, FAAFP, AFP Contributing Editor, is a clinical assistant professor in the department of family medicine at Michigan State University, East Lansing.

Address correspondence to Michelle Nelson, MD, at michelle.nelson@mclaren.org

Author Disclosure: No relevant financial relationships.

Coverage of guidelines from other organizations does not imply endorsement by AFP or the AAFP.

This series is coordinated by Michael J. Arnold, MD, MHPE, AFP Assistant Medical Editor.

A collection of Practice Guidelines published in AFP is available at https://www.aafp.org/afp/practguide.

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