Infectious Diseases Society of America

These are some of the highlights of the guidelines without analysis or commentary. For more information, go directly to the guidelines by clicking the link in the reference.

December 05, 2024

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Updated recommendations on risk assessment, diagnostic imaging, and microbiologic evaluation of complicated intra-abdominal infections in adults, children, and pregnant people were published in October 2024 by the Infectious Diseases Society of America in Clinical Infectious Diseases.^[1]

The following are all conditional recommendations unless noted otherwise.

To manage complicated intra-abdominal infection, it is essential to stratify patients’ risk on the basis of their illness severity. For affected adults in whom a severity of illness score is used, the APACHE II (Acute Physiology And Chronic Health Evaluation II) is preferred for risk stratification within 24 hours of admission to the hospital or intensive care unit.

Appendicitis

In the setting of nonpregnant adults who are suspected of having acute appendicitis, the suggested initial imaging modality to make the diagnosis is an abdominal computed tomography (CT) scan.

For children, adolescents, and pregnant people with suspected acute appendicitis, abdominal ultrasonography (US) is the suggested initial diagnostic imaging modality. If the initial US result is equivocal or nondiagnostic in children and teenagers and there is continuing clinical suspicion, an abdominal magnetic resonance image (MRI) or CT scan is suggested as the next diagnostic imaging, not another US. If the initial US result is equivocal or nondiagnostic in pregnant individuals and clinical suspicion remains, an MRI is suggested as the next diagnostic imaging.

In the setting of uncomplicated appendicitis in adults and children who are having an appendectomy, routine intra-abdominal cultures are NOT suggested.

Acute Cholecystitis/Acute Cholangitis

In the setting of nonpregnant adults who are suspected of having acute cholecystitis or acute cholangitis, the suggested initial diagnostic imaging is an abdominal US. If the initial US findings are equivocal or nondiagnostic, an abdominal CT scan is suggested as the next imaging modality to diagnose acute cholecystitis or acute cholangitis.

If both the US and CT findings are equivocal or nondiagnostic in nonpregnant individuals with suspected acute cholecystitis and clinical suspicion remains, it is suggested that either an abdominal MRI/MR cholangiopancreatography (MRCP) or hepatobiliary iminodiacetic acid (HIDA) scan be the subsequent diagnostic imaging (knowledge gap for MRI/MRCP).

In pregnant individuals with suspected acute cholecystitis or suspected acute cholangitis, either US or MRI can be considered for the initial diagnostic imaging modality; neither is recommended over the other (knowledge gap).

Acute Diverticulitis

In nonpregnant adults who are suspected of having acute diverticulitis, an abdominal CT scan is the suggested initial diagnostic imaging. If CT is unavailable or contraindicated, an abdominal US or MRI is suggested as the initial diagnostic modality.

In pregnant individuals with suspected acute diverticulitis, either US or MRI can be considered for diagnostic imaging; neither is recommended over the other (knowledge gap).

Intra-abdominal Abscesses

In nonpregnant adults and adolescents who are suspected of having an acute intra-abdominal abscess, an abdominal CT scan is the suggested initial diagnostic imaging. However, in children with suspected acute intra-abdominal abscess, an abdominal US is the suggested initial diagnostic imaging; if findings from this initial US in this young population are negative/equivocal/nondiagnostic and clinical suspicion remains, either CT scanning or MRI is suggested as the next diagnostic imaging.

In pregnant individuals with suspected acute intra-abdominal abscess, either US or MRI can be considered as the initial diagnostic imaging; neither is recommended over the other (knowledge gap).

In the setting of adults and children with suspected intra-abdominal infections and an elevated temperature AND: low blood pressure and/or rapid breathing and/or delirium, OR a concern exists for antibiotic-resistant organisms that would affect the treatment regimen, obtaining blood cultures is suggested.

Routine blood cultures are NOT suggested in the setting of non-immunocompromised adults and children with suspected intra-abdominal infections with a normal/elevated temperature but in whom hypotension, tachypnea, or delirium are absent, and no concern exists for antibiotic-resistant organisms that would affect the treatment regimen.

Obtaining intra-abdominal cultures to guide antimicrobial therapy is suggested for adults and children with complicated intra-abdominal infection undergoing a procedure for source control.

For more information, please go to Appendicitis, Pediatric Appendicitis, Appendicitis Imaging, Acute Cholecystitis, Pediatric Cholecystitis, Acute Cholangitis, Diverticulitis of the Colon Imaging and Diagnosis, Abdominal Abscess, Peritonitis and Abdominal Sepsis, and Surgical Approach to Peritonitis and Abdominal Sepsis.