Complicated Intra-abdominal Infections: Risk Assessment, Diagnostic Imaging, and Microbiological Evaluation in Adults, Children, and Pregnant People

Publication Date: June 13, 2024
Last Updated: June 25, 2024

Summary of Recommendations

Risk stratification according to severity of illness is important for management of complicated intra-abdominal infection. For adults with complicated intra-abdominal infection, if a severity of illness score is used, the panel suggests APACHE II (Acute Physiology Age Chronic Health Evaluation II) as the preferred severity of illness score for risk stratification within 24 hours of hospital or ICU admission. ( W , L)
Remarks:
  • Because the WSES (World Society of Emergency Surgery) Sepsis Severity Score is specific to complicated intra-abdominal infection and performs well, it is an acceptable alternative to APACHE II for adults with complicated intra-abdominal infection.
  • No severity of illness scoring system specific to complicated intra-abdominal infection can be recommended to guide management of pediatric patients with complicated intra-abdominal infection at present.
705
In non-pregnant adults with suspected acute appendicitis, the panel suggests obtaining an abdominal CT as the initial imaging modality to diagnose acute appendicitis. ( W , VL)
Remarks:
  • IV contrast is usually appropriate whenever a CT is obtained in adults with suspected acute appendicitis; however, CT without IV contrast also has high diagnostic accuracy in detecting acute appendicitis and may be appropriate.1
  • Because of CT’s accuracy, immediate additional imaging studies beyond CT are usually not necessary. If a CT is negative but clinical suspicion for acute appendicitis persists, consider observation and supportive care, with or without antibiotics; if clinical suspicion is high, consider surgical intervention.
  • US, when definitively positive or definitively negative, and MRI are also reasonably accurate and may precede CT, depending on the patient and clinical circumstances.
705
In children and adolescents with suspected acute appendicitis, the panel suggests obtaining an abdominal US as the initial imaging modality to diagnose acute appendicitis. ( W , VL)
Remarks:
  • US is generally readily available but is also operator-dependent and can yield equivocal results. MRI is not always readily available, and sedation may be required for young children. CT is generally readily available but involves radiation exposure and may require use of IV contrast or sedation.
705
In children and adolescents with suspected acute appendicitis, if initial US is equivocal/non-diagnostic and clinical suspicion persists, the panel suggests obtaining an abdominal MRI or CT as subsequent imaging to diagnose acute appendicitis rather than obtaining another US. ( W , VL)
Remarks:
  • US is generally available but is also operator-dependent and can yield equivocal results. MRI is not always readily available, and sedation may be required for young children. CT is generally readily available but involves radiation exposure and may require use of IV contrast or sedation.
  • CT with IV contrast is usually appropriate when performed in children with suspected acute appendicitis after equivocal ultrasound; however, CT without IV contrast may be appropriate.1
  • Depending on the clinical situation, observation may be appropriate instead of subsequent imaging.
  • If there is a strong clinical suspicion for appendicitis after equivocal imaging, exploratory laparoscopy or laparotomy may also be considered if subsequent imaging delays appropriate management.
705
In pregnant people with suspected acute appendicitis, the panel suggests obtaining an abdominal US as the initial imaging modality to diagnose acute appendicitis. ( W , VL)
Remarks:
  • It would also be reasonable to initially obtain an MRI in pregnant people with suspected acute appendicitis if access to an MRI is readily available. The conditional imaging strategy suggested (US, then MRI for equivocal results) would likely yield the same results as an MRI only.
705
In pregnant people with suspected acute appendicitis, if initial US is equivocal/non-diagnostic and clinical suspicion persists, the panel suggests obtaining an MRI as subsequent imaging to diagnose acute appendicitis. ( W , VL)
Remarks:
  • It would also be reasonable to initially obtain an MRI in pregnant people with suspected acute appendicitis if access to an MRI is readily available. The conditional imaging strategy suggested (US, then MRI for equivocal results) would likely yield the same results as an MRI only.
705
In non-pregnant adults with suspected acute cholecystitis or acute cholangitis, the panel suggests abdominal US as the initial diagnostic imaging modality. ( W , VL)
Remarks:
  • The diagnosis of acute cholangitis should include clinical signs (jaundice, fever, chills, and right upper quadrant abdominal pain), laboratory findings (indicators of inflammation and biliary stasis), and imaging findings (biliary dilatation, or evidence of an etiology, e.g., stricture, stone, obstructing mass).
  • We did not identify any studies assessing the accuracy of abdominal US or CT for the diagnosis of acute cholangitis and relied on indirect evidence from acute cholecystitis.
  • Because acute cholecystitis and acute cholangitis are uncommon in children, we did not systematically review the evidence for children; however, it would be reasonable to mirror the imaging pathway for adults in children.
705
In non-pregnant adults with suspected acute cholecystitis or acute cholangitis, if initial US is equivocal/non-diagnostic and clinical suspicion persists, the panel suggests obtaining an abdominal CT scan as subsequent imaging to diagnose acute cholecystitis or acute cholangitis. ( W , VL)
Remarks:
  • The diagnosis of acute cholangitis should include clinical signs (jaundice, fever, chills, and right upper quadrant abdominal pain), laboratory findings (indicators of inflammation and biliary stasis), and imaging findings (biliary dilatation, or evidence of an etiology, e.g., stricture, stone, obstructing mass).
  • CT with IV contrast is preferable and usually appropriate when CT is obtained for subsequent imaging.1
  • We did not identify any studies assessing the accuracy of abdominal US or CT for the diagnosis of acute cholangitis and relied on indirect evidence from acute cholecystitis.
  • Because acute cholecystitis and acute cholangitis are uncommon in children, we did not systematically review the evidence for children; however, it would be reasonable to mirror the imaging pathway for adults in children.
705
In non-pregnant adults with suspected acute cholecystitis, if both US and CT are equivocal/non-diagnostic and clinical suspicion persists, the panel suggests obtaining either an abdominal MRI/MRCP (magnetic resonance cholangiopancreatography) or hepatobiliary iminodiacetic acid (HIDA) scan as subsequent imaging to diagnose acute cholecystitis (low certainty of evidence for HIDA, knowledge gap for MRI/MRCP). ( W , )
Remarks:
  • If both abdominal US and CT are inconclusive but acute cholangitis is suspected, MRI/MRCP is a reasonable option.
  • The diagnosis of acute cholangitis should include clinical signs (jaundice, fever, chills, and right upper quadrant abdominal pain), laboratory findings (indicators of inflammation and biliary stasis), and imaging findings (biliary dilatation, or evidence of an etiology, e.g., stricture, stone, obstructing mass).
  • Because acute cholecystitis and acute cholangitis are uncommon in children, we did not systematically review the evidence for children; however, it would be reasonable to mirror the imaging pathway for adults in children.
705
In pregnant people with suspected acute cholecystitis or suspected acute cholangitis, US or MRI can be considered as the initial diagnostic imaging modality; however, the panel is unable to recommend one imaging modality versus the other. (K, G)
Remarks:
  • The diagnosis of acute cholangitis should include clinical signs (jaundice, fever, chills, and right upper quadrant abdominal pain), laboratory findings (indicators of inflammation and biliary stasis), and imaging findings (biliary dilatation, or evidence of an etiology, e.g., stricture, stone, obstructing mass).
705
In non-pregnant adults with suspected acute diverticulitis, the panel suggests obtaining an abdominal CT as the initial diagnostic modality. ( W , VL)
Remarks:
  • IV contrast is usually appropriate whenever a CT is obtained and can be helpful to characterize and detect subtle bowel wall abnormalities and complications of diverticulitis; however, CT without IV contrast may be appropriate.
705
In non-pregnant adults with suspected acute diverticulitis, if CT is unavailable or contraindicated, the panel suggests obtaining an US or MRI as the initial diagnostic modality. ( W , VL)
705
In pregnant adults with suspected acute diverticulitis, US or MRI can be considered for imaging; however, the panel is unable to recommend one imaging modality versus the other. (K, G)
705
In non-pregnant adults and adolescents with suspected acute intra-abdominal abscess, we suggest obtaining an abdominal CT as the initial diagnostic imaging modality. ( W , VL)
Remarks:
  • When CT is obtained, the use of intravenous contrast may improve visualization of the abscess wall. Because of CT’s accuracy, immediate additional imaging studies beyond CT should not be necessary.
705
In children with suspected acute intra-abdominal abscess, we suggest obtaining an abdominal US as the initial diagnostic imaging modality. ( W , VL)
Remarks:
  • At least one study1 suggests MRI as a reasonable option for initial imaging of suspected acute intra-abdominal abscess in children.
  • US is generally available but is also operator-dependent and can yield equivocal results. MRI is not always readily available, and sedation may be required for young children. CT is generally readily available but involves radiation exposure and may require use of IV contrast or sedation.
705
In children with suspected acute intra-abdominal abscess, if initial US is equivocal/non-diagnostic and clinical suspicion persists, the panel suggests either CT or MRI as subsequent imaging to diagnose acute intra-abdominal abscess. ( W , VL)
Remarks:
  • US is generally available but is also operator-dependent and can yield equivocal results. MRI is not always readily available, and sedation may be required for young children. CT is generally readily available but involves radiation exposure and may require use of IV contrast or sedation.
705
In pregnant people with suspected acute intra-abdominal abscess, US or MRI can be considered as the initial diagnostic imaging modality; however, the panel is unable to recommend one versus the other. (K, G)
705
In adults and children with suspected intra-abdominal infections who have an elevated temperature AND: hypotension and/or tachypnea and/or delirium, OR there is concern for antibiotic-resistant organisms that would inform the treatment regimen, we suggest obtaining blood cultures. ( W , VL)
Remarks:
  • Direct evidence on obtaining blood cultures in patients with intra-abdominal infections is lacking.
  • Concern for antibiotic-resistant organisms includes high rates of regional resistance to commonly used agents administered as empiric treatment for intra-abdominal infections, patient history of any colonization or infection with organisms not susceptible to commonly used empiric regimens within the previous 90 days, antibiotic treatment within the previous 90 days, elderly or immunocompromised patients or patients with other significant comorbidities, and/or healthcare-associated infection.
  • Clinicians should use their best judgment considering the benefits and risks of performing blood cultures. In select cases (e.g., concern for antibiotic-resistant organisms, concern for ascending cholangitis, complex intra-abdominal abscess), blood cultures may be helpful to assist with clinical decision-making and further management. Concern for antibiotic-resistant organisms includes high rates of regional resistance to commonly used agents administered as empiric treatment for intra-abdominal infections, patient history of any colonization or infection with organisms not susceptible to commonly used empiric regimens within the previous 90 days, antibiotic treatment within the previous 90 days, elderly or immunocompromised patients or patients with other significant comorbidities, and/or healthcare-associated infection.
705
In non-immunocompromised adults and children with suspected intra-abdominal infections who have a normal/elevated temperature but do not have hypotension, tachypnea, or delirium, and there is no concern for antibiotic-resistant organisms that would inform the treatment regimen, we suggest not routinely obtaining blood cultures. (very low certainty of evidence for adults/low certainty of evidence for children). ( W , )
Remarks:
  • Direct evidence on obtaining blood cultures in patients with intra-abdominal infections is lacking.
  • Clinicians should use their best judgment considering the benefits and risks of performing blood cultures. In select cases (e.g., concern for antibiotic-resistant organisms, concern for ascending cholangitis, complex intra-abdominal abscess), blood cultures may be helpful to assist with clinical decision-making and further management. Concern for antibiotic-resistant organisms includes high rates of regional resistance to commonly used agents administered as empiric treatment for intra-abdominal infections, patient history of any colonization or infection with organisms not susceptible to commonly used empiric regimens within the previous 90 days, antibiotic treatment within the previous 90 days, elderly or immunocompromised patients or patients with other significant comorbidities, and/or healthcare-associated infection.
705
In adults and children with complicated intra-abdominal infection who are having a procedure for source control, we suggest obtaining intra-abdominal cultures to guide antimicrobial therapy. ( W , M)
705
In adults and children with uncomplicated appendicitis undergoing an appendectomy, we suggest not routinely obtaining intra-abdominal cultures. ( W , L)
Remarks:
  • Immunocompromised patients are at increased risk for antibiotic-resistant organisms and intra-abdominal cultures are generally warranted.
  • At the time of surgery, if complicated disease is suspected/recognized, intra-abdominal cultures may be advised.
705

Recommendation Grading

Disclaimer

The information in this patient summary should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.

Overview

Title

Complicated Intra-abdominal Infections: Risk Assessment, Diagnostic Imaging, and Microbiological Evaluation in Adults, Children, and Pregnant People

Authoring Organization

Infectious Diseases Society of America

Publication Month/Year

June 13, 2024

Last Updated Month/Year

June 25, 2024

Supplemental Implementation Tools

Document Type

Guideline

Country of Publication

US

Document Objectives

As the first part of an update to the clinical practice guideline on the diagnosis and management of complicated intra-abdominal infections in adults, children, and pregnant people, developed by the Infectious Diseases Society of America, we present 21 updated recommendations. These recommendations span risk assessment, diagnostic imaging, and microbiological evaluation. The panel’s recommendations are based upon evidence derived from systematic literature reviews and adhere to a standardized methodology for rating the certainty of evidence and strength of recommendation according to the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach.

Inclusion Criteria

Male, Female, Adolescent, Adult, Child, Older adult

Health Care Settings

Ambulatory, Hospital, Laboratory services, Outpatient

Intended Users

Nurse, nurse practitioner, physician, physician assistant

Scope

Diagnosis, Assessment and screening, Management

Keywords

cIAI, abdominal infections, Complicated Intra-abdominal Infections

Supplemental Methodology Resources

Data Supplement

Methodology

Number of Source Documents
189
Literature Search Start Date
October 22, 2022
Literature Search End Date
June 13, 2024