2025+ACR适宜性标准：急性左上腹疼痛

ACR Appropriateness Criteria® Acute Left Upper Quadrant Pain

Expert Panel on Gastrointestinal Imaging: Sahar Soleimani, MD, PhD a, Ihab R. Kamel, MD, PhD b, Kevin J. Chang, MDc, Twyla B. Bartel, DO, MBA d, Priya R. Bhosale, MDe, Brooks D. Cash, MDf, Victoria Chernyak, MD, MSg,Robin A. Felker, MDh,Ayushi Gupta, MDi, Hao S. Lo, MD, MBA J, Michael Magnetta, MDk,Richard D. Shih, MDl, Joseph H. Yacoub, MDm, Kathryn J. Fowler, MDn

Abstract

Acute abdominal pain is one of the most common chief complaints encountered in the emergency department and outpatient setting.Across all sites, the left upper quadrant(LUQ) is the least common location for abdominal pain with reportedly the lowest physical examination interrater agreement. The limited sensitivity of physical examination, combined with an uncommon and nonspecific clinical presentation, make assessment of LUQ pain challenging. Acute LUQ pain may arise directly from the spleen or infections in the LUQ, or represent referred pain from other organs such as stomach, bowells, pancreas, or kidney.This document aims to address acute pain with suspected splenomegaly, with fever, and not otherwise specified. CT abdomen and pelvis with contrast is usually appropriate for detection of a broad range of pathologies. In patients with suspected splenomegaly, ultrasound abdomen is also usually an appropriate alternate for initial imaging.

${}^{a}$ Research Author, Johns Hopkins Hospital, Baltimore, Maryland.

${ }^{b}$ University of Colorado Denver Anschzuch Medical Campus, Aurora,

${}^{6}$ Panel Chair, Boston University Medical Center, Boston, Massachusetts.

dGlobal Advanced Imaging, PLLC, Little Rock, Arkansas, ACR Com-mission on Nuclear Medicine and Molecular Imaging.

`The University of Texas MDanerson Cancer Center, Houston, Texas'University of Texas Health Science Center at Houston and McGovern Medical School, Houston, Texas; American Gastroenterological Association.`

Association.

${ }^{8}$ Columbia University Irving Medical Center, New York, New York.

hMedstar Georgetown University Hospital, Washington, District of Columbia, Primary care physician.

${}^{1}$ Emory University School of Medicine, Atlanta, Georgia.

<BeginOfPara>UMass Memorial Health and UMass Chan Medical School, Worcester,Massachusetts: ACR Committee on Emergency Radiology-GSER.

kNorth Shore University HealthSystem, Evanston, Illinois.

${}^{1}$ Schmidt College of Medicine, Florida Atlantic University, Boca Raton,Florida; American College of Emergency Physicians.

“Loyola University of Chicago, Chicago, Illinois?

"Speciality Chair, University of California San Diego, San Diego,California.

Corresponding author: Ihab R. Kamel, MD, PhD, UCHHealth University of Colorado Hospital (UCH), 12605 E 16th Ave, Aurora, CO 80045;e-mail:ihab.kamel@cuanschutz.edu.

The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document.Reprint requests to: publications@acr.org.

Victoria Chernyak, MD, MS, reports a relationship with Bayer as a consultant. Kathryn J. Fowler, MD, reports financial support was provided by Bayer Corporation; reports a relationship with Bayer AG that includes consulting or advisory, speaking and lecture fees, and travel reimburse-ment; a relationship with Ascelia Pharma AB that includes consulting or advisory; a relationship with CME Science that includes speaking and lecture fees and travel reimbursement; and is an RSNA editorial board member. Joseph H. Yacoub, MD, reports a relationship with Microsoft Corporation that includes consulting or advisory. The other authors state that they have no conflict of interest related to the material discussed in this article. Twyla B. Bartel, DO, MBA, and Kathryn J. Fowler, MD, are partners; Sahaleimani MD, PhD, is on partnership track; and all other authors are nonpartner/nonpartnership track/employees.

The ACR Appropriateness Criteria documents are updated regularly.Please go to the ACR website at http://www.acr.org/Clinical-Resources/Clinical-Tools-and-Reference/Appropriateness-Criteria to confirm that you are accessing the most current content.

Discipline: The ACR Committee on Appropriateness Criteria and its expert panels have developed criteria for determining appropriate imaging examinations for diagnosis and treatment of specified medical condition(s). These criteria are intended to guide radiologists, radiation oncologists and referring physicians in making decisions regarding radiologic imaging and treatment.Generally, the complexity and severity of a patient's clinical condition should dictate the selection of appropriate imaging procedures or treatments. Only those examinations generally used for evaluation of the patient's condition are ranked. Other imaging studies necessary to evaluate other cointenetic diseases or other medical consequences of this condition are not considered in this document. The availability of equipment or personnel may influence the selection of appropriate imaging procedures or treatments. Imaging techniques classified as investigational by the FDA have not been considered in developing these criteria; however, study of new equipment and applications should be encouraged. The ultimate decision regarding the appropriateness of any specific radiologic examination or treatment must be made by the referring physician and radiologist in light of all the circumstances presented in an individual examination.

The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RANDU/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Key Words: Appropriaten Criteria, Appropriate Use Criteria, AUC, acute abdominal pain, CT, left upper quadrant (LUQ),splenomegaly, ultrasound (US)

J Am Coll Radiol 2025;22:S481-S491. © 2025 American College of Radiology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, Al training, and similar technologies.

ACR Appropriateness Criteria® Acute Left Upper Quadrant Pain. Variants 1 to 3 and Tables 1 and 2.

Variant 1. Adult. Acute left upper quadrant pain. Suspected splenomegaly. Initial imaging.

|Procedure|Appropriateness Category|Relative Radiation Level| |---|---|---| |US abdomen|Usually Appropriate|0| |CT abdomen and pelvis with IV contrast|Usually Appropriate|0| |MRI abdomen without and with IV contrast|May Be Appropriate|0| |MRI abdomen without IV contrast|May Be Appropriate|0| |CT abdomen and pelvis without IV contrast|May Be Appropriate|0| |Radiography abdomen|Usually Not Appropriate|0| |CT abdomen and pelvis without and with IV|Usually Not Appropriate|0| |CT abdomen and pelvis without and with IV contrast|Usually Not Appropriate|0| |FDG-PET/CT skull base to mid-thigh|Usually Not Appropriate|0|

Variant 2. Adult. Acute left upper quadrant pain. Fever. Initial imaging.

|Procedure|Appropriateness Category|Relative Radiation Level| |---|---|---| |CT abdomen and pelvis with IV contrast|Usually Appropriate|$$\begin{array}{l}\\ \\ \\ \\ \\ \\ \\ \\ \end{array}$$| |US abdomen|May Be Appropriate|O| |MRI abdomen without and with IV contrast|May Be Appropriate|O| |MRI abdomen without IV contrast|May Be Appropriate|O| |CT abdomen and pelvis without IV contrast|May Be Appropriate|O| |Radiography abdomen|Usually Not Appropriate|8| |CT abdomen and pelvis without and with IV contrast|Usually Not Appropriate|8| |CT abdomen and pelvis without and with IV contrast|Usually Not Appropriate|8| |FDG-PET/CT skull base to mid-thigh|Upou|8|

Variant 3. Adult. Acute left upper quadrant pain. Not otherwise specified. Initial imaging.

|Procedure|Appropriateness Category|Relative Radiation Level| |---|---|---| |CT abdomen and pelvis with IV contrast|Usually Appropriate|888| |US abdomen|May Be Appropriate|0| |MRI abdomen without and with IV contrast|May Be Appropriate|0| |CT abdomen and pelvis without IV contrast|May Be Appropriate|88| |Radiography abdomen|Usually Not Appropriate|88| |MRI abdomen without IV contrast|Usually Not Appropriate|88| |CT abdomen and pelvis without and with IV contrast|Usually Not Appropriate|88| |FDG-PET/CT skull base to mid-thigh|Usually Not Appropriate|88|

Table 1. Appropriateness category names and definitions

|Appropriateness Category|Appropriateness|Appropriateness Category| |---|---|---| |Name|Rating|Appropriateness Category Definition| |Usually Appropriate|7,8, or 9|The imaging procedure or treatment is indicated in the specified clinical scenarios at a favorable risk-benefit ratio for patients.| |May Be Appropriate|4,5, or 6|The imaging procedure or treatment may be indicated in the specified clinical scenarios as an alternative to imaging procedures or treatments with a more favorable risk-benefit ratio, or the risk-benefit ratio for patients is equivocal.| |May Be Appropriate (Disagreement)|5|The individual ratings are too dispersed from the panel median. The different label provides transparency regarding the panel's recommendation."May be appropriate" is the rating category and a rating of 5 is assigned.| |Usually Not Appropriate|1,2, or 3|The imaging procedure or treatment is unlikely to be indicated in the specified clinical scenarios, or the risk-benefit ratio for patients is likely to be unfavorable.|

Table 2. Relative radiation level designations

|RRL|Adult Effective Dose Estimate Range (mSv)|Pediatric Effective Dose Estimate Range (mSv)| |---|---|---| |0|0|0| ||<0.1|<0.03| ||0.1-1|0.03-0.3| ||1-10|0.3-3| ||10-30|3-10| ||30-100|10-30|

Note: Relative radiation level (RRL) assignments for some of the examinations cannot be made, because the actual patient doses in these procedures vary as a function of a number of factors (eg, region of the body exposed to ionizing radiation, the imaging guidance that is used). The RRLs for these examinations are designated as "varies."

SUMMARY OF LITERATURE REVIEW

Introduction/Background

Acute abdominal pain is one of the most common chief complaints encountered in the emergency department and outpatient setting [1]. Physical examination plays a key role in determining the urgency of the problem and the subsequent diagnostic plan. Across all sites, the left upper quadrant(LUQ) is the least common location for abdominal pain with <5% of patients localizing their pain specifically to the LUQ [2], with reportedly the lowest physical examination interrater agreement among attendings and trainees [3,4].The limited sensitivity of physical examination combined with an uncommon and nonspecific clinical presentation makes assessment of LUQ pain challenging. Delays in diagnosis and complications in management lead to more adverse outcomes, especially in the elderly, who are often unable to provide reliable histories and suffer from many comorbidities [5].

Anatomically, the LUQ contains the spleen, stomach,bowel, pancreas, left lobe of the liver, left kidney, and left adrenal gland. LUQ pain in a significant majority of pa-tients is a referred pain, most commonly from peptic ulcer disease, gastritis, esophagitis, pancreatitis, renal colic, car-diac angina, or pericarditis [6-8]. Less commonly, pleutitic pain such as in pneumonia or osseous pain such as in spinal stress fractures or metastases may present as referred LUQ.These topics have been addressed with dedicated references to each topic such as the ACR Appropriateness Criteria topics on "Epigastric Pain"[9], "Acute Pancreatitis" [10],"Acute Onset Flank Pain-Suspicion of Stone Disease(Urolithiasis)" [11], "Acute Pyelonephritis" [12], "Acute Nonspecific Chest Pain-Low Probability of Coronary Ar-tery Disease" [13], "Acute Respiratory Illness in Immunocompetent Patients" [14], "Thoracic Back Pain"[15], and "Acute Nonlocalized Abdominal Pain"[16].

This document aims to address clinical scenarios in which reported acute LUQ pain is not suspected to arise from the above mentioned etiologies and is uniquely arising from the LUQ. In this setting, suspected or known spleno-megaly from underlying hematologic disorders, malignancy,liver disease, or viral illness may present with LUQ pain without any specific physical examination findings or labo-ratory marker abnormalities. Splenomegaly increases the risk of splenic infarction, rupture, torsion, aneurysmal rupture, or venous thrombosis [8,17,18]. The presence of fever in addition to LUQ pain often requires urgent diagnostic workup because fever raises concern for intraabdominal infection, abscess, or hematologic malignancy.

<BeginOfPara>This document provides a framework for initial imaging evaluation of patients with acute LUQ pain in the setting of known or suspected splenomegaly, acute LUQ pain with

fever, and acute LUQ pain not otherwise specified. The rating and recommendations for this document specifically relate to adult nonpregnant patients unless otherwise stated.Contraindications, availability, and cost are not considered in the appropriateness assessment.

Initial Imaging Definition

Initial Imaging Definition is defined as imaging at the beginning of the care episode for the medical condition defined by the variant. More than one procedure can be considered usually appropriate in the initial imaging evaluation when:

\>There are procedures that are equivalent alternatives (ie,only one procedure will be ordered to provide the clinical information to effectively manage the patient's care)

OR

\>There are complementary procedures (ie, more than one procedure is ordered as a set or simultaneously where each procedure provides unique clinical information to effectively manage the patient's care).

DISCUSSION OF PROCEDURES BY VARIANT

Variant 1: Adult. Acute left upper quadrant pain. Suspected splenomegaly. Initial imaging

Past medical history or physical examination may raise concern for splenomegaly with or without the presence of pain.Common causes of splenomegaly include infections such as mononucleosis (in the setting of Epstein-Barr virus), granu-lomatous infections, portal hypertension, sickle cell disease,lymphoproliferative disorders, sarcoidosis, or metastasis.Splenomegaly with capsular expansion can cause pain and increases the risk of splenic rupture, infarction, hematoma,microabscesses, and susceptibility to trauma [17-19]. In sickle cell disease, acute LUQ pain with a sudden drop in hematocrit suggests splenic sequestration, which increases the risk of shock and death [20,21]. Vascular complications such as venous thrombosis or arterial pseudoaneurysm may present with pain and are usually a harbinger of serious underlying conditions. Pancreatitis,pancreatic cancer, inflammatory bowel disease, other inflammatory processes, or hypercoagulopathic states may lead to splenic venous thrombosis. Splenic artery ruptured aneurysm or pseudoaneurysm can present with LUQ pain, although these lesions are increasingly found incidentally at the present time [22].

CT Abdomen and Pelvis With IV Contrast. CT is the workhorse of diagnostic abdominal imaging and the preferred choice in a broad range of clinical presentations,

including acute abdominal pain [23-25]. CT abdomen and pelvis can be performed with intravenous (IV) and/or oral contrast administration, commonly acquired during a single venous phase. IV contrast improves visualization of small structures, enhances delineation of normal from abnormal visceral parenchyma, and better depicts the gastrointestinal wall lining [26,27]. High-density positive oral contrast is used for evaluation of a potential leak, fis-tula, or differentiation of small bowel loops from lymph nodes or peritoneal implants. In the acute setting, oral contrast may lead to a delay in throughput and scan acquisition without a definite diagnostic value. Positive oral contrast may also obscure gastrointestinal lining or intra-luminal masses, or create pseudotumors in the stomach[28,29]. High-volume low-density neutral contrast, such as water, improves gastrointestinal luminal evaluation without the above mentioned problems.

In a retrospective study of LUQ pain in the emergency department, CT was reported to have a 69% sensitivity to detect an acute abdominal abnormality[25]. Of those patients with an abnormality detected, 27% had an acute abnormal CT finding that represented the cause of their pain. Of the remaining patients, 12% were diagnosed clinically with a pathology that was undetectable on imaging. The remaining patients with negative CT were not found to have a significant pathology by clinical evaluation. The authors concluded that CT is a useful tool for patients with LUQ pain in the emergency setting with moderate sensitivity and excellent specificity[25].

CT is highly sensitive for the detection of splenic infarction and its underlying cause. Retrospective studies demonstrated the superiority of CT with IV contrast over other modalities in splenic infarct from microvascular involvement such as in sickle cell disease, thromboembolic causes in endocarditis or cardiac thrombus, and global infarction from advanced pancreatic cancer, splenic torsion,or vascular intervention[17,30].

CT is also an excellent tool for the visualization and volumetric quantification of the spleen. Splenomegaly detected and monitored by CT can be a marker of disease progression in hematologic disorders and impact manage-ment [31-33]. The pattern of splenic enhancement as well as the presence of abnormal vascularity and collateralization on CT with IV contrast can aid in the diagnosis of cirrhotic and noncirthotic portal hypertension, associated splenomegaly,gastropathy, or variceal bleeding [26,27]. CT is also well suited to the evaluation of infiltrative processes such as lymphoma or sarcoidosis, which may present with splenomegaly, a solitary splenic mass, or micronodular or macronodular splenic infiltration [34].

This superior anatomical delineation of CT makes it a valuable tool in detecting complications such as the

development of infection, fluid collections, and pseudoa-neurysms and impacts their management with CT-guided interventions [35,36].

CT Abdomen and Pelvis Without and With IV Contrast. The addition of noncontrast CT to routine CT with IV contrast is helpful in the differentiation of calcifi-cations and surgical material from contrast enhancement.However, in the setting of acute LUQ pain, the additional noncontrast examination is of limited diagnostic value and comes with a longer examination time.

CT Abdomen and Pelvis Without IV Contrast. The absence of IV contrast limits the evaluation of vasculature and diminishes the conspicuity of small structures and the gastrointestinal lining. More specifically, splenic infarcts and small lesions may appear isodense to normal splenic parenchyma on noncontrast CT. However, splenomegaly,lymphadenopathy, hematoma, and fluid collections can be characterized on noncontrast CT, and therefore, it may still be useful in the workup of LUQ pain.

FDG-PET/CT Skull Base to Mid-Thigh. Fluorine-18-2-fluoro-2-deoxy-D-glucose(FDG)-PET/CT has been used in the workup of splenomegaly, fever, lymphadenopathy,immunocompromised patients who may suffer from lym-phoma, fungal infection, and other miscellaneous infections and malignancies. However, this modality does not provide adequate information to enable differentiation of these di-agnoses, and it is primarily used to find an appropriate target for tissue biopsy [37]. There is no literature on the usefulness of PET/CT as an initial imaging modality in the acute setting.

MRI Abdomen Without IV Contrast. Although there are limited studies on the usefulness of MRI specifically for LUQ pain, rapid MRI studies have been introduced and optimized for the evaluation of acute abdominal and pelvic pain. In a systematic review paper of 33 studies in 2,044 pa-tients, MRI achieved a 96% sensitivity and 93% specificity for the diagnosis of appendicitis and its complications [38]. In a study of abbreviated rapid MRI without IV contrast in acute abdominal pain in 468 patients, MRI achieved an overall diagnostic accuracy of 99% [39]. In a subgroup of patients who underwent surgery or endoscopy (n= 90), the sensitivity was 98% and the specificity was 92%. The most common etiologies were appendicitis, bowel obstruction,intusensionc, inflammatory bowel disease, diverticulitis,abscess, ovarian torsion, and pelvic inflammatory disease[39]. MRI can be a useful tool in pregnant patients and children. In addition, MRI has been well studied and concluded to be a useful tool for evaluation of splenic size,mass, micronodularity, and infiltrative process [40,41].Splenic hematoma, infarct, and perisplenic collections can also be evaluated by MRI.

MRI Abdomen Without and With IV Contrast. There are no large, published studies that investigate the value of contrast administration and compared with MRI without IV contrast in the workup of acute LUQ pain with sus-pected splenomegaly. However, the addition of IV contrast can improve the evaluation of the splenic parenchyma,masses, infarcts, and the vasculature, and therefore, it is recommended to be considered for the initial workup.

Radiography Abdomen. Radiographs achieve a sensi-tivity of 90% for identifying foreign bodies and a moderate sensitivity of 49% for detecting bowel obstruction[42].Radiography has historically been used in the evaluation of splenomegaly[43]; however, low-dose CT demon-strates superior diagnostic accuracy in comparison. It is now concluded that there is a limited role for radiography in the assessment of acute LUQ pain and splenomegaly.

US Abdomen. Ultrasound (US) has a lower diagnostic accuracy compared with cross-sectional modalities such as CT and MRI. A retrospective study reported an US sensi-tivity of 18% in the detection of splenic inferacts that were diagnosed by CT over a 10-year period at a single center [30].Similarly, US has inferior sensitivity in the detection of splenic lesions and infiltrative processes. However, it can be useful in screening and assessing splenic size and perisplenic collections and enables serial imaging to monitor for complications. Two decades ago, patients with sickle cell disease were expected to have autosplenectomy by age 5,which is now a rare observation, primarily due to advances in supportive care and transfusion therapy. US provides an excellent noninvasive tool for accurate assessment of spleen size as well as evaluation of echogenicity and heterogeneity,which varies with disease severity [44,45]. US has also been reported in the evaluation of splenomegaly and guidance for safe return to contract sports after infectious mononucleosis[46,47].

Color and spectral Doppler US can aid in the evaluation of vasculature. Portal flow parameters and the splenic artery resistive index provide useful tools in differentiating between splenomegaly of portal hypertension or hematologic origins[48]. US can also aid in the evaluation of portal and splenic vein thrombosis, which is a common cause of portal hypertension and splenomegaly, with a high morbidity from gastrointestinal bleeding [49,50]. Therefore, US provides an appropriate tool for initial imaging of the LUQ in the emergency, inpatient, or outpatient settings. In this document, US refers to formal sonographic examination.Comparison with Focused Assessment with Sonography in Trauma examination or point-of-care US is beyond the scope of this document and will be investigated and addressed in future publications by the ACR.

Variant 2: Adult. Acute left upper quadrant pain. Fever. Initial imaging

Localized LUQ pain and fever raise concern for an infec-tious process with possible abscess, especially with a known systemic infection, malignancy, immunocompromised state, recent surgery, or significant trauma. Infection in the LUQ may involve superinfection of a splenic lesion or he-matoma or be the result of hematogenous spread from a systemic infection such as endocarditis or direct extension from subjacent infection such as pancreatitis or diverticulitis[8]. Timely diagnosis of an abscess is critical for source control and to avoid rupture and peritonitis.

CT Abdomen and Pelvis With IV Contrast. CT pro-vides a rapid and high-resolution cross-sectional imaging tool for the evaluation of acute abdominal pain and fever [23-25].Administration of IV contrast increases the diagnostic yield through the better characterization of visceral parenchyma,intraorgan abscases, and intraperitoneal or retroperitoneal fluid collections. IV contrast improves visualization of the gastrointestinal tract and the presence of inflammatory,infectious, or ischemic colitis, which may present with LUQ pain [8]. Positive oral contrast can assist in the evaluation of potential leak and fistula, but it introduces logistical challenges including prolonged scan time without a significant diagnostic yield in the setting of intraabdominal infection. CT was reported to have a 69%sensitivity to detect an acute abnormality in a retrospective study of patients with LUQ pain presenting in the emergency department [25]. CT achieved an excellent specificity, with only 12% of patients with negative CT diagnosed clinically with a pathology that was undetectable on imaging. The remaining patients with negative CT also had an unremarkable clinical evaluation [25]. Although there is no study in the current literature assessing the diagnostic accuracy of CT specifically in acute LUQ pain and fever, there is sufficient evidence on the usefulness of CT with IV contrast to properly diagnose and guide the workup of acute abdominal pain and fever. In a retrospective study of 584 patients, emergency department clinicians were surveyed before and after a CT of the abdomen [51]. CT altered the leading diagnosis in 49% of patients, increased mean physician diagnostic certainty ranging from 70% to 92%, and led to changes in management in 42% of patients.Among etiologies associated with fever and infection, including abscess, diverticulitis, colitis, cholecystitis, cholangitis, and appendicitis, CT increased diagnostic certainty in>30% of cases[51]. CT also provides a safe modality for diagnosis and percutaneous drainage of abscesses. Specifically for splenic abscesses, CT-guided drainage has shown to be an effective alternative to splenectomy in select cases to preserve immunity[36].

CT Abdomen and Pelvis Without and With IV Contrast. In select postoperative patients with ambiguity about surgical history or concern for retained surgical ma-terial, noncontrast CT may assist in the differentiation of foreign bodies from abnormal enhancement. However, in the setting of acute LUQ pain and fever, the addition of noncontrast CT to routine CT with IV contrast does not increase the diagnostic yield or add information.

CT Abdomen and Pelvis Without IV Contrast.

Although CT with IV contrast is superior, most notably for the assessment of vasculature and gastrointestinal lining in colitis and gastroenteritis, CT without IV contrast can be used as a substitute for evaluation of fluid collections and abscesses as a potential source for fever. In patients at increased risk of microabscasses such as in immunocom-promised patients, IV contrast is more sensitive for the detection of numerous small lesions in the spleen and should be considered as the initial imaging modality[8].

FDG-PET/CT Skull Base to Mid-Thigh. FDG-PET/CT with large anatomical coverage and high sensitivity to inflammatory, infectious, and neoplastic etiologies is useful in the workup of fever of unknown origin, especially if prior cross-sectional imaging did not identify a source [37].However, there is no current literature to support the use of this modality for the initial workup of LUQ pain and fever.

MRI Abdomen Without IV Contrast. MRI has been used for the evaluation of acute pain and specifically for the detection of abdominepivicb ascesses [39,52]. Rapid protocols with T2 and diffusion-weighted imaging sequences without IV contrast have been optimized and validated with an overall diagnostic accuracy of 99% in a range of etiologies including enterocolitis, pyonephritis, appendicitis, divicultirels, and associated abscess [39]. MRI also allows for the differentiation of an abscess from other fluid collections such as hematomas or postoperative collections. More advanced protocols such as MR enterography can be considered in patients with suspected inflammatory bowel disease, which preferably should be performed with IV contrast to increase the sensitivity for detection of mild inflammatory changes, fistula tracts, and small abscesses [53]. However, these examinations require a bowel preparation and advanced planning,potentially leading to delays in the emergency setting.Additionally, MRI requires patient cooperation and the ability to perform repeated breath-holds and lie flat for an extended period, which may not be a realistic goal for critically ill patients,resulting in incomplete examinations.

MRI Abdomen Without and With IV Contrast. MRI without IV contrast allows for the detection of inflamma-tory changes, abscesses, and lymphadenopathy and provides

adequate anatomical information [39,52,53]. However, IV contrast enhances the visualization and detection of mild inflammation, fistula tracts, and masses, as well as evaluation of vasculature and potential complications such as pseudoaneurysms or venous thrombus. Although diffusion-weighted imaging sequences may be adequate for evaluation of abscesses in patients with LUQ pain and fever, they are highly susceptible to artifacts, most notably in the presence of metallic implants or foreign bodies.Addition of IV contrast can address these instances and it is recommended to be included.

Radiography Abdomen. The current literature does not include any recent studies on the use of radiography in the evaluation of LUQ pain and fever or its role in detection of the underlying cause. If there is concern for foreign body or surgical material causing fever and pain, radiography can be considered, because it has been shown to achieve a sensi-tivity of 90% in the detection of intraabdominal foreign bodies [42].

US Abdomen. US provides a fast tool for the visualization of anatomic landmarks in the LUQ such as the spleen,pancreatic tail, or left kidney and evaluation of vasculature,with the assistance of color and spectral Doppler US. It also allows for the detection of intrasplenic lesions, perisplenic collections, and ascites. However, US sensitivity drops at earlier stages of disease and performs inferiorly compared with CT. In a retrospective study of 240 patients with colonic diverticulitis, the sensitivity of US for diagnosing complicated diverticulitis in comparison with CT as the reference standard was 84%, with a specificity of 95.8%[54]. Similarly, in a study of 85 patients with suspected intraabdominal sepsis after abdominal surgery, the likelihood ratio of a positive test was 1.33 for US and 2.53 for CT[55]. Corresponding posttest probabilities were 0.57 for US and 0.71 for CT. The likelihood ratio of a negative result was 0.6 for US and 0.18 for CT.Corresponding posttest probabilities were 0.37 for US and 0.15 for CT. The authors concluded that because of the low discriminatory power, US should not be performed as an initial test in the detection of intraabdominal infections[55]. Nonetheless, US can be a useful modality for targeted interventions and drainage of associated abscesses following initial diagnosis.

Variant 3: Adult. Acute left upper quadrant pain. Not otherwise specified. Initial imaging Localized LUQ pain in the absence of splenomegaly or fever has a broad differential including peptic ulcer disease,gastric outlet obstruction, pancreatitis and its complica-tions, infectious or ischemic enterocolitis, diverticulitis,

bowel obstruction, adrenal hemorrhage, renal etiologies,neoplasm, hernias, postoperative complications, and pul-monary etiologies such as pneumonia or pericarditis. In the absence of ancillary findings to suggest a specific diagnosis,many of which are individually addressed by other ACR Appropriateness Criteria® as noted in the introduction of this document, the initial imaging study needs to be broad.CT is often the modality of choice and the first to be performed.

CT Abdomen and Pelvis With IV Contrast. The workhorse of abdominal imaging, CT abdomen and pelvis,is the preferred choice for the evaluation of abdominal pain in the presence or absence of other ancillary symptoms [16].It is rapid, and it provides a large field of view with adequate anatomical coverage and high spatial resolution. IV contrast increases soft tissue contrast and allows for the evaluation of vasculature or acute bleeding in suspect cases. Positive oral contrast is beneficial in the evaluation for suspected leaks,fistulas, and postoperative complications; however, it is not routinely required. It may create the appearance of pseudotumors in the stomach or cause streak artifacts in the bowel [28,29]. Neutral oral contrast, such as water, allows for better distention and evaluation of stomach and bowel lumen, without significant delay in throughput.

In a retrospective study of 1,280 patients by 245 physi-cians, CT led to a change in the leading diagnosis in 51% of patients with abdominal pain, 42% of patients with chest pain and/or dyspnea, and 24% of patients with headache[24]. Pre-CT diagnostic confidence was inversely associated with the likelihood of a diagnostic change. CT helped confirm or exclude>95% of alternative diagnoses and led to changes in admission decisions for 25% of patients with abdominal pain[24]. This unparalleled impact on the confirmation of a final diagnosis, alleviation of uncertainty,and selection of appropriate clinical management has led to a robust and growing use of CT in the emergency and outpatient setting. Although there are limited studies on nonspecific LUQ pain, there is evidence that CT will outperform other modalities and should be considered as the initial imaging modality. In a study of 100 patients who presented to the emergency department with acute LUQ pain, the sensitivity of CT was 69% for 39 patients who were eventually diagnosed with an acute abdominal abnormality[25]. Of these, 27 patients had an abnormal finding that was detected on CT. Of the remaining patients with negative CT, 12 patients were diagnosed clinically without detectable image findings. The remaining patients with negative CT were not found to have a significant pathology by clinical evaluation. It is concluded that CT is a useful tool for patients with LUQ pain in the

emergency setting with moderate sensitivity and excellent specificity.

CT Abdomen and Pelvis Without and With IV Contrast. In select patients with a complex past surgical history and no prior in-house imaging, the addition of a noncontrast CT may reduce ambiguity about surgical ma-terial versus abnormal enhancement. However, noncontrast CT does not significantly increase the diagnostic yield in nearly all other patients presenting with nonspecific LUQ pain, and therefore it is not useful on a routine basis.

CT Abdomen and Pelvis Without IV Contrast. He-matoma, fluid collections, ascites, bowel obstruction,lymphadenopathy, hepatosplenomegaly, and renal stones are common etiologies that do not require the administration of IV contrast. However, inflammatory and infectious pro-cesses, such as gastroenteritis, pancreatitis, pyelonephritis,inflammatory bowel disease, colitis, venous thrombus, or neoplasms, can be missed on noncontrast examination.

FDG-PET/CT Skull Base to Mid-Thigh. FDG-PET/CT may be used for the workup of malignancy and select nonmalignant etiologies such as fever of unknown origin,suspected infection of instrumentation and prostheses, or paraneoplastic syndromes, but it is not a useful initial im-aging study for evaluation of pain, localized to LUQ or otherwise.

MRI Abdomen Without IV Contrast. With the advent of rapid sequences, MRI achieves high diagnostic accuracy for the workup of abdominal pain. However, absence of IV contrast lowers diagnostic yield in many circumstances.Examples include mild inflammatory changes, infarcts, fis-tula tracts, vasculature, and their complications such as pseudoaneurysms or thrombus. For this reason, MRI without IV contrast is not recommended for patients with LUQ pain that is otherwise nonspecific and who require an imaging examination that encompasses a wide range of etiologies.

MRI Abdomen Without and With IV Contrast. MRI achieves high diagnostic accuracy for the workup of abdominal pain, specifically in appendicitis, inflammatory bowel disease, pancreatitis, biliary, and ovarian etiologies,and has been well studied in pregnant patients and children.Therefore, it may be an appropriate initial imaging mo-dality for LUQ pain workup.

Radiography Abdomen. Radiographs with or without serial imaging were traditionally used for the evaluation of bowel obstruction, ileus, and constipation, with moderate sensitivity ranging from 30% to 70% [56]. Bowel obstruction,however, infrequently presents as a localized pain. For

nonobstructive etiologies, radiography is also inferior to CT.In a study of $>800$ patients in the emergency department,abdominal radiography contributed to clinical management in 4% of patients [57]. As a result, radiography may lead to a delay in care and invariably requires subsequent imaging and is thus not recommended.

US Abdomen. US provides a rapid tool for the evaluation of splenic size, splenic vasculature, and the preliminary screening of the LUQ for a mass or abscess [46,58]. However, it is of vital importance to consider the inferior sensitivity of US to cross-sectional modalities for patients with nonspecific LUQ pain. US abdomen may be appropriate in a select group of patients in whom US is not deemed to cause a delay in care.Additionally, it should not be planned as a complementary procedure to cross-sectional modalities.

SUMMARY OF HIGHLIGHTS

This is a summary of the key recommendations from the variant tables. Refer to the complete narrative document for more information.

■Variant 1: In the setting of LUQ pain with suspected splenomegaly, CT abdomen and pelvis with IV contrast is usually appropriate to evaluate the spleen. US abdomen is also usually appropriate to evaluate splenise size and parenchyma, as well as splenic and portal vasculature. These procedures should be viewed as alternate initial procedures, although in certain circumstances, they may be ordered in sequence. It is not recommended that these procedures be ordered simultaneously.

■Variant 2: In the setting of LUQ pain with fever, CT abdomen and pelvis with IV contrast is usually appropriate to evaluate for an infectious process with or without abscess involving spleen or adjacent organs.

■Variant 3: In the setting of LUQ pain, not otherwise specified, CT abdomen pelvis with IV contrast is usually appropriate to evaluate a wide range of pathologies and is the modality of choice.

SUPPORTING DOCUMENTS

The evidence table, literature search, and appendix for this topic are available at https://acsearch.acr.org/list. The ap-pendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation.

<BeginOfPara>For additional information on the Appropriateness Criteria methodology and other supporting documents,visit www.acr.org/Clinical-Resources/Clinical-Tools-and-Reference/Appropriateness-Criteria.

GENDER EQUALITY AND INCLUSIVITY CLAUSE

The ACR acknowledgees the limitations in applying inclu-sive language when citing research studies that predates the use of the current understanding of language inclusive of diversity in sex, intersex, gender, and gender-diverse people.The data variables regarding sex and gender used in the cited literature will not be changed. However, this guideline will use the terminology and definitions as proposed by the National Institutes of Health[59].

RELATIVE RADIATION LEVEL INFORMATION

Potential adverse health effects associated with radiation exposure are an important factor to consider when selecting the appropriate imaging procedure. Because there is a wide range of radiation exposures associated with different diagnostic pro-cedures, a relative radiation level (RRL) indication has been included for each imaging examination. The RRLs are based on effective dose, which is a radiation dose quantity that is used to estimate population total radiation risk associated with an imaging procedure. Patients in the pediatric age group are at inherently higher risk from exposure, because of both organ sensitivity and longer life expectancy (relevant to the long $\underline{la}$ tency that appears to accompany radiation exposure). For these reasons, the RRL dose estimate ranges for pediatric examina-tions are lower as compared with those specified for adults (see Table 2). Additional information regarding radiation dose assessment for imaging examinations can be found in the ACR Appropriateness Criteria $\underline{R}$ Radiation Dose Assessment Introduction document [60].

ACKNOWLEDGMENTS

The ACR is the sole funding source of the ACR AC.

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