Clinical Infectious Diseases
IDSA GUIDELINES
2024 Clinical Practice Guideline Update by the
Infectious Diseases Society of America on Complicated
Intra-abdominal Infections: Diagnostic Imaging
of Suspected Acute Appendicitis in Adults, Children,
and Pregnant People
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Robert A. Bonomo,1,2,3,4 Pranita D. Tamma,5 Fredrick M. Abrahamian,6,7 Mary Bessesen,8,9 Anthony W. Chow,10 E. Patchen Dellinger,11 Morven S. Edwards,12
Ellie Goldstein,13 Mary K. Hayden,14 Romney Humphries,15 Keith S. Kaye,16 Brian A. Potoski,17 Jesús Rodríguez-Baño,18 Robert Sawyer,19 Marion Skalweit,20
David R. Snydman,21 Katelyn Donnelly,22 and Jennifer Loveless22
1
Medical Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio, USA; 2Clinician Scientist Investigator, Research Service, Louis Stokes Cleveland
Department of Veterans Affairs Medical Center, Cleveland, Ohio, USA; 3Departments of Medicine, Pharmacology, Molecular Biology and Microbiology, Biochemistry, and Proteomics and
Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA; 4CWRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES)
Cleveland, Ohio, USA; 5Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; 6Department of Emergency Medicine, Olive View–University of California,
Los Angeles (UCLA) Medical Center, Sylmar, California, USA; 7David Geffen School of Medicine at UCLA, Los Angeles, California, USA; 8Department of Medicine, Veterans Affairs Eastern Colorado
Health Care, Aurora, Colorado, USA; 9Division of Infectious Diseases, University of Colorado School of Medicine, Aurora, Colorado, USA; 10Department of Medicine, University of British Columbia,
Vancouver, British Columbia, Canada; 11Department of Surgery, University of Washington, Seattle, Washington, USA; 12Division of Infectious Diseases, Department of Pediatrics, Baylor College of
Medicine, Houston, Texas, USA; 13RM Alden Research Laboratory, Santa Monica, California, USA; 14Division of Infectious Diseases, Department of Medicine, Rush University Medical Center,
Chicago, Illinois, USA; 15Division of Laboratory Medicine, Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA; 16Division of
Allergy, Immunology and Infectious Diseases, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA; 17Department of Pharmacy and Therapeutics, University of
Pittsburgh School of Pharmacy, Pittsburgh, Pennsylvania, USA; 18Division of Infectious Diseases and Microbiology, Department of Medicine, Hospital Universitario Virgen Macarena, University of
Seville, Biomedicines Institute of Seville-Consejo Superior de Investigaciones Científicas, Seville, Spain; 19Department of Surgery, Western Michigan University Homer Stryker MD School of
Medicine, Kalamazoo, Michigan, USA; 20Department of Medicine and Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA; 21Division of Geographic Medicine
and Infectious Diseases, Tufts Medical Center, Boston, Massachusetts, USA; and 22Clinical Affairs and Practice Guidelines, Infectious Diseases Society of America, Arlington, Virginia, USA
This paper is part of a clinical practice guideline update on the risk assessment, diagnostic imaging, and microbiological evaluation
of complicated intra-abdominal infections in adults, children, and pregnant people, developed by the Infectious Diseases Society of
America (IDSA). In this paper, the panel provides recommendations for diagnostic imaging of suspected acute appendicitis. The
panel’s recommendations are based on 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.
Keywords. intra-abdominal infection; appendicitis; guideline; diagnostic imaging; radiology.
In adults with suspected acute appendicitis, should ultra Recommendation: In non-pregnant adults with suspected acute
sound (US), computed tomography (CT), or magnetic reso appendicitis, the panel suggests obtaining an abdominal CT
nance imaging (MRI) be obtained as the initial imaging as the initial imaging modality to diagnose acute appendicitis
modality? (conditional recommendation, very low certainty of evidence).
In adults with suspected appendicitis, if initial imaging is Remarks:
inconclusive, should US, CT, or MRI be obtained for subse
• Intravenous (IV) contrast is usually appropriate whenever a CT
quent imaging?
is obtained in adults with suspected acute appendicitis; howev
er, CT without IV contrast also has high diagnostic accuracy in
detecting acute appendicitis and may be appropriate [1].
Received 19 June 2024; editorial decision 21 June 2024; published online 4 July 2024 • Because of the accuracy of CT, immediate additional imaging
Correspondence: R. A. Bonomo, MD, Center for Antimicrobial Resistance and Epidemiology,
Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, Cleveland, OH 44106
studies beyond CT are usually not necessary. If a CT is negative
(practiceguidelines@idsociety.org). but clinical suspicion for acute appendicitis persists, consider
Clinical Infectious Diseases® 2024;79(9):S94–103 observation and supportive care, with or without antibiotics; if
© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases
Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com clinical suspicion is high, consider surgical intervention.
for reprints and translation rights for reprints. All other permissions can be obtained through our • Ultrasound, when definitively positive or definitively nega
RightsLink service via the Permissions link on the article page on our site—for further information
please contact journals.permissions@oup.com.
tive, and MRI are also reasonably accurate and may precede
https://doi.org/10.1093/cid/ciae348 CT, depending on the patient and clinical circumstances.
S94 • CID 2024:79 (15 October) • Bonomo et al
, In children with suspected acute appendicitis, should US, Remarks:
CT, or MRI be obtained as the initial imaging modality?
• It would also be reasonable to initially obtain an MRI in preg
In children with suspected appendicitis, if initial imaging
nant people with suspected acute appendicitis if access to
is inconclusive, should US, CT, or MRI be obtained for sub
MRI is readily available. The conditional imaging strategy
sequent imaging?
suggested (US, then MRI for equivocal results) would likely
Recommendation: In children and adolescents with suspect
yield the same results as an MRI only.
ed acute appendicitis, the panel suggests obtaining an abdom
inal US as the initial imaging modality to diagnose acute
Recommendation: In pregnant people with suspected acute
appendicitis (conditional recommendation, very low certainty
appendicitis, if initial US is equivocal/non-diagnostic and clin
of evidence).
ical suspicion persists, the panel suggests obtaining an MRI as
Remarks:
subsequent imaging to diagnose acute appendicitis (conditional
Downloaded from https://academic.oup.com/cid/article/79/Supplement_3/S94/7706132 by guest on 17 October 2024
• Ultrasound is generally readily available but is also recommendation, very low certainty of evidence).
operator-dependent and can yield equivocal results. MRI Remarks:
is not always readily available, and sedation may be re
• It would also be reasonable to initially obtain an MRI in preg
quired for young children. CT is generally readily available
nant people with suspected acute appendicitis if access to
but involves radiation exposure and may require use of IV
MRI is readily available. The conditional imaging strategy
contrast or sedation.
suggested (US, then MRI for equivocal results) would likely
Recommendation: In children and adolescents with suspected yield the same results as an MRI only.
acute appendicitis, if initial US is equivocal/non-diagnostic and
INTRODUCTION
clinical suspicion persists, the panel suggests obtaining an ab
dominal MRI or CT as subsequent imaging to diagnose acute This paper is part of a clinical practice guideline update on the
appendicitis rather than obtaining another US (conditional rec risk assessment, diagnostic imaging, and microbiological eval
ommendation, very low certainty of evidence). uation of complicated intra-abdominal infections in adults,
Remarks: children, and pregnant people, developed by the Infectious
Diseases Society of America [3–9]. Here, the guideline panel
• Ultrasound is generally available but is also operator-
provides recommendations for diagnostic imaging of suspected
dependent and can yield equivocal results. MRI is not always
acute appendicitis in adults, children, and pregnant people.
readily available, and sedation may be required for young
Recommendations are stratified by initial imaging and then
children. CT is generally readily available but involves radia
subsequent imaging if initial imaging is inconclusive. These
tion exposure and may require use of IV contrast or sedation.
recommendations replace previous statements in the last itera
• CT with IV contrast is usually appropriate when performed
tion of this guideline [10].
in children with suspected acute appendicitis after equivocal
A complicated intra-abdominal infection extends beyond the
US; however, CT without IV contrast may be appropriate [2].
hollow viscus of origin into the peritoneal space and is associated
• Depending on the clinical situation, observation may be ap
with either abscess formation or peritonitis; this term is not meant
propriate instead of subsequent imaging.
to describe the infection’s severity or anatomy. An uncomplicated
• If there is a strong clinical suspicion for appendicitis after
intra-abdominal infection involves intramural inflammation of
equivocal imaging, exploratory laparoscopy or laparotomy
the gastrointestinal tract and has a substantial probability of pro
may also be considered if subsequent imaging delays appro
gressing to complicated infection if not adequately treated.
priate management.
These recommendations are intended for use by healthcare
professionals who care for patients with suspected intra-
In pregnant people with suspected acute appendicitis,
abdominal infections.
should US or MRI be obtained as the initial imaging
modality?
METHODS
In pregnant people with suspected appendicitis, if initial
imaging is inconclusive, should US or MRI be obtained for The panel’s recommendations are based on evidence derived
subsequent imaging? from systematic literature reviews and adhere to a standardized
Recommendation: In pregnant people with suspected acute methodology for rating the certainty of evidence and strength of
appendicitis, the panel suggests obtaining an abdominal recommendation according to the GRADE (Grading of
US as the initial imaging modality to diagnose acute ap Recommendations Assessment, Development, and Evaluation)
pendicitis (conditional recommendation, very low certainty approach (Supplementary Figure 1) [11]. The recommendations
of evidence). have been endorsed by the European Society of Clinical
IDSA Guideline on Complicated Intra-abdominal Infections: Diagnostic Imaging of Suspected Appendicitis • CID 2024:79 (15 October) • S95
