This is the current release of the guideline.

This guideline updates a previous version: Bree RL, Rosen MP, Foley WD, Gay SB, Grant TH, Heiken JP, Huprich JE, Lalani T, Miller FH, Ros PR, Sudakoff GS, Greene FL, Rockey DC, Expert Panel on Gastrointestinal Imaging. ACR Appropriateness Criteria® right lower quadrant pain. [online publication]. Reston (VA): American College of Radiology (ACR); 2007. 5 p. [35 references]

The appropriateness criteria are reviewed biennially and updated by the panels as needed, depending on introduction of new and highly significant scientific evidence.

Right lower quadrant pain and suspected appendicitis

To evaluate the appropriateness of initial radiologic examinations for patients with right lower quadrant pain and suspected appendicitis

Patients with right lower quadrant pain and suspected appendicitis

Utility of radiologic examinations in differential diagnosis

Literature Search Procedure

The Medline literature search is based on keywords provided by the topic author. The two general classes of keywords are those related to the condition (e.g., ankle pain, fever) and those that describe the diagnostic or therapeutic intervention of interest (e.g., mammography, MRI).

The search terms and parameters are manipulated to produce the most relevant, current evidence to address the American College of Radiology Appropriateness Criteria (ACR AC) topic being reviewed or developed. Combining the clinical conditions and diagnostic modalities or therapeutic procedures narrows the search to be relevant to the topic. Exploding the term "diagnostic imaging" captures relevant results for diagnostic topics.

The following criteria/limits are used in the searches:

1. Articles that have abstracts available and are concerned with humans
2. Restrict the search to the year prior to the last topic update or in some cases the author of the topic may specify which year range to use in the search. For new topics, the year range is restricted to the last 5 years unless the topic author provides other instructions.
3. May restrict the search to Adults only or Pediatrics only.
4. Articles consisting of only summaries or case reports are often excluded from final results.

The search strategy may be revised to improve the output as needed.

The total number of source documents identified as the result of the literature search is not known.

Strength of Evidence Key

Category 1 - The conclusions of the study are valid and strongly supported by study design, analysis and results.

Category 2 - The conclusions of the study are likely valid, but study design does not permit certainty.

Category 3 - The conclusions of the study may be valid but the evidence supporting the conclusions is inconclusive or equivocal.

Category 4 - The conclusions of the study may not be valid because the evidence may not be reliable given the study design or analysis.

The topic author drafts or revises the narrative text summarizing the evidence found in the literature. American College of Radiology (ACR) staff draft an evidence table based on the analysis of the selected literature. These tables rate the strength of the evidence for all articles included in the narrative text.

The expert panel reviews the narrative text, evidence table, and the supporting literature for each of the topic-variant combinations and assigns an appropriateness rating for each procedure listed in the table. Each individual panel member forms his/her own opinion based on his/her interpretation of the available evidence.

More information about the evidence table development process can be found in the American College of Radiology (ACR) Appropriateness Criteria® Evidence Table Development document (see "Availability of Companion Documents" field).

Modified Delphi Technique

When the data available from existing scientific studies are insufficient, the American College of Radiology Appropriateness Criteria (ACR AC) employs systematic consensus techniques to determine appropriateness. The ACR AC panels use a modified Delphi technique to determine the rating for a specific procedure. A series of surveys are conducted to elicit each individual panelist's expert opinion of the appropriateness of an imaging or therapeutic procedure for a specific clinical scenario based on the available data. ACR staff distributes surveys to the panelists along with the evidence table and narrative. Each panelist interprets the available evidence and rates each procedure. Voting surveys are completed by panelists without consulting other panelists. The ratings are integers on a scale between 1 and 9, where 1 means the panel member feels the procedure is "least appropriate" and 9 means the panel member feels the procedure is "most appropriate". Each panel member has one vote per round to assign a rating. The surveys are collected and de-identified and the results are tabulated and redistributed after each round. A maximum of three rounds are conducted. The modified Delphi technique enables each panelist to express individual interpretations of the evidence and his or her expert opinion without excessive bias from fellow panelists in a simple, standardized and economical process.

Consensus among the panel members must be achieved to determine the final rating for each procedure. If eighty percent (80%) of the panel members agree on a single rating or one of two consecutive ratings, the final rating is determined by the rating that is closest to the median of all the ratings. Up to three voting rounds are conducted to achieve consensus.

If consensus is not reached through the modified Delphi technique, the panel is convened by conference call. The strengths and weaknesses of each imaging examination or procedure are discussed and a final rating is proposed. If the panelists on the call agree, the rating is accepted as the panel's consensus. The document is circulated to all the panelists to make the final determination. If consensus cannot be reached, "No consensus" appears in the rating column and the reasons for this decision are added to the comment sections.

Not applicable

Criteria developed by the Expert Panels are reviewed by the American College of Radiology (ACR) Committee on Appropriateness Criteria.

ACR Appropriateness Criteria®

Clinical Condition: Right Lower Quadrant Pain--Suspected Appendicitis

Variant 1: Fever, leukocytosis, and classic presentation clinically for appendicitis in adults.

Radiologic Procedure	Rating	Comments	RRL*
CT abdomen and pelvis with contrast	8	Use of oral or rectal contrast depends on institutional preference.
CT abdomen and pelvis without contrast	7	Use of oral or rectal contrast depends on institutional preference.
US abdomen RLQ	6	With graded compression.	O
US pelvis	5		O
X-ray abdomen	5	May be useful in excluding free air or obstruction.
MRI abdomen and pelvis without and with contrast	5	See statement regarding contrast in text under "Anticipated Exceptions."	O
CT abdomen and pelvis without and with contrast	4	Use of oral or rectal contrast depends on institutional preference.
MRI abdomen and pelvis without contrast	4		O
X-ray contrast enema	3
Tc-99m WBC scan abdomen and pelvis	3
Rating Scale: 1,2,3 Usually not appropriate; 4,5,6 May be appropriate; 7,8,9 Usually appropriate			*Relative Radiation Level

Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.

Variant 2: Fever, leukocytosis; possible appendicitis, atypical presentation, adults and adolescents.

Radiologic Procedure	Rating	Comments	RRL*
CT abdomen and pelvis with contrast	8	Use of oral or rectal contrast depends on institutional preference.
X-ray abdomen	6	May be useful in excluding free air or obstruction.
US abdomen RLQ	6	With graded compression.	O
US pelvis	6		O
CT abdomen and pelvis without contrast	6	Use of oral or rectal contrast depends on institutional preference.
MRI abdomen and pelvis without and with contrast	5	See statement regarding contrast in text under "Anticipated Exceptions."	O
CT abdomen and pelvis without and with contrast	4	Use of oral or rectal contrast depends on institutional preference.
MRI abdomen and pelvis without contrast	4		O
X-ray contrast enema	3	The RRL for the adult procedure is .
Tc-99m WBC scan abdomen and pelvis	3
Rating Scale: 1,2,3 Usually not appropriate; 4,5,6 May be appropriate; 7,8,9 Usually appropriate			*Relative Radiation Level

Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.

Variant 3: Fever, leukocytosis, pregnant woman.

Radiologic Procedure	Rating	Comments	RRL*
US abdomen RLQ	8	With graded compression. Better in first and early second trimester.	O
MRI abdomen and pelvis without contrast	7	May be useful following negative or equivocal US.	O
US pelvis	6		O
CT abdomen and pelvis with contrast	6	Use of oral or rectal contrast depends on institutional preference.
CT abdomen and pelvis without contrast	5	Use of oral or rectal contrast depends on institutional preference.
CT abdomen and pelvis without and with contrast	5	Use of oral or rectal contrast depends on institutional preference.
MRI abdomen and pelvis without and with contrast	4	See statement regarding contrast in text under "Anticipated Exceptions."	O
X-ray abdomen	2
X-ray contrast enema	2
Tc-99m WBC scan abdomen and pelvis	2
Rating Scale: 1,2,3 Usually not appropriate; 4,5,6 May be appropriate; 7,8,9 Usually appropriate			*Relative Radiation Level

Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.

Variant 4: Fever, leukocytosis, possible appendicitis, atypical presentation in children (less than 14 years of age).

Radiologic Procedure	Rating	Comments	RRL*
US abdomen RLQ	8	With graded compression.	O
CT abdomen and pelvis with contrast	7	May be useful following negative or equivocal US. Use of oral or rectal contrast depends on institutional preference. Consider limited RLQ CT.
X-ray abdomen	6	May be useful in excluding free air or obstruction.
US pelvis	5		O
CT abdomen and pelvis without contrast	5	Use of oral or rectal contrast depends on institutional preference. Consider limited RLQ CT.
MRI abdomen and pelvis without and with contrast	5	See statement regarding contrast in text under "Anticipated Exceptions."	O
CT abdomen and pelvis without and with contrast	4	Use of oral or rectal contrast depends on institutional preference. Consider limited RLQ CT.
MRI abdomen and pelvis without contrast	4		O
X-ray contrast enema	3
Tc-99m WBC scan abdomen and pelvis	2
Rating Scale: 1,2,3 Usually not appropriate; 4,5,6 May be appropriate; 7,8,9 Usually appropriate			*Relative Radiation Level

Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.

Summary of Literature Review

Few comparative imaging studies evaluating right lower quadrant pain are available. Most imaging reports center on disease processes, such as appendicitis. Because appendicitis is the most common cause of right lower quadrant pain, the focus of this narrative is on appendicitis and the accuracy of imaging procedures in diagnosing appendicitis, although consideration of other diseases is, of course, included.

Acute appendicitis is the most common acute abdominal disorder that requires surgery. In most patients with acute appendicitis, imaging may not be necessary, because the clinical presentation is sufficiently diagnostic to allow surgery. Clinical prediction scores, such as the Alvarado score, have been used as a prediction rule for identifying patients with appendicitis. However, the accuracy of these clinically-based scores is inferior to imaging. In the published studies for imaging in appendicitis, the selection criteria for imaging are not often stated, but in most investigations, subjects with definitive clinical examination findings of appendicitis undergo operation without imaging. In the reported imaging studies, an average of 45% to 50% of imaged subjects had appendicitis, and 36% had nonspecific abdominal pain. Data on the overall effect of imaging on surgical treatment of appendicitis and patient outcome remain contradictory.

Radiographic diagnosis is of limited value for diagnosing acute appendicitis, except in occasional circumstances when an appendicolith or other ancillary findings are identified. Although barium enema has been used historically to diagnose appendicitis, it depends on the negative finding of nonvisualization of the appendix and may be quite uncomfortable in patients with acute appendicitis. Nonetheless, barium small-bowel follow-through or barium enema may be useful following cross-sectional imaging studies, for other causes of right lower quadrant pain, including suspected small- bowel obstruction, infectious ileitis, and inflammatory bowel disease. (See the NGC summary of the ACR Appropriateness Criteria® on Suspected Small Bowel Obstruction.)

Computed Tomography and Ultrasound

Computed tomography (CT) is the most accurate study for evaluating patients without a clear clinical diagnosis of acute appendicitis. In a meta-analysis of six prospective studies through February 2006 of the accuracy of CT and ultrasound (US) in adolescents and adults, CT demonstrated superior sensitivity (91%, 95% confidence interval [CI], 84% to 95%) and specificity (90%; 95% CI, 85% to 94%) versus US (sensitivity 78%; 95% CI, 67% to 86%; specificity 83%, 95% CI, 76% to 88%). The results of investigations of CT showed consistent results across all studies and institutions, while US investigations demonstrated heterogeneity, suggesting greater dependence on operator skill. Small studies suggest that thinner slices and multiplanar reformats increase confidence in identifying the appendix.

The routine use of CT to evaluate for appendicitis has also been shown to decrease overall costs by $447 to $1,412 per patient, and has been shown to decrease the negative appendectomy rate from 42.9% to 7.1% among women aged 18 to 45 years. While it has been suggested that perhaps nonpregnant females of child-bearing age be worked up with a different imaging algorithm due to increased possibility of alternative diagnoses to appendicitis, such as gynecological etiologies, no studies have directly addressed this issue to a sufficient degree. Clinical accuracy in diagnosing right lower quadrant pain in women of child-bearing age tends to be less accurate compared with adult men, thereby suggesting a lower threshold for imaging in this population.

Another question is whether to use intravenous (IV) contrast in the CT evaluation of appendicitis. High accuracy has been reported for both techniques, but the few direct comparisons available in the literature suggest higher accuracy when IV contrast is used. A prospective study with 232 patients showed that noncontrast enhanced CT (sensitivity, 90%; specificity, 86%) was inferior to rectal-only contrast (sensitivity, 93%; specificity, 95%) and IV and oral contrast (sensitivity, 100%; specificity, 89%). In lieu of individual patient contraindications to IV contrast, its use is recommended in evaluation of right lower quadrant abdominal pain. However, if IV contrast is contraindicated, noncontrast enhanced CT has been shown to have sensitivity of 96%, specificity of 99%, and accuracy of 97%.

Other questions regarding CT protocol include the use of oral versus rectal contrast. A recent study has shown similar sensitivity and specificity for detection of acute appendicitis on 64-row multidetector CT (MDCT) with or without oral contrast performed with intravenous contrast. The use of rectal contrast has been shown to decrease the emergency department stay by greater than one hour in one prospective study, without a significant difference in patient satisfaction or discomfort. There is concern, however, that rectal contrast can be complicated by bowel perforation, with a cited number similar to barium enema of 0.04%. To the guideline panel's knowledge, no prospective comparison studies evaluating the two are available in the literature. Institutional experience may be the best determinant of oral versus rectal contrast use.

Both CT and US may be effective in detecting causes of pain unrelated to appendicitis. The range of diseases studied includes inflammatory bowel disease, infectious bowel disease, small-bowel obstruction, acute gynecological conditions, and others.

CT appears superior to US in evaluating patients with periappendiceal abscess, especially when the abscesses become large. CT can be used to choose among different therapeutic options, including antibiotic treatment (with small abscesses), percutaneous drainage (with one to three well-defined medium-sized abscesses), and surgery (with extensive abnormality not amenable to percutaneous drainage).

Magnetic Resonance Imaging

At this time, there are few studies evaluating the value of magnetic resonance imaging (MRI) in the general population for acute appendicitis. MRI is desirable due to its lack of ionizing radiation; however, it is limited due to its higher cost, slower acquisition time, and lesser clinical availability. Several small, retrospective studies cite sensitivity of 97% to 100% and specificity of 92% to 94%; one prospective study of 138 patients exhibited a sensitivity of 100% and specificity of 99%. It is anticipated that as MRI becomes more clinically available in the emergency setting, the value of MRI for right lower quadrant pain will be further elucidated.

Pediatric Patients

CT and US have been less well evaluated in children than in adults, but there are increasing data on imaging use in the pediatric population. Several factors are unique in children, including increased radiosensitivity to ionizing radiation and smaller body size and less body fat, favoring initial use of US. A systematic literature review in July 2004 revealed eight prospective evaluations of US for appendicitis in children. The pooled sensitivity of graded-compression US was 91% (95% CI, 89% to 93%), and the specificity was 97% (95% CI, 95% to 99%). A meta-analysis published in October 2006 included 26 studies of US and CT — 15 prospective and 11 retrospective, in the pediatric population. The pooled sensitivity of US was 88% (95% CI, 86% to 90%) and specificity of 94% (95% CI, 92% to 95%) compared with CT, which exhibited a pooled sensitivity of 94% (95% CI, 92% to 97%) and specificity of 95% (95% CI, 94% to 97%). These results suggest that although CT is more accurate, US is nearly as good in experienced hands, and given the lack of ionizing radiation, is the preferred examination in children, particularly if equivocal results are followed up by CT. Thus the CT- after US-approach appears to have excellent accuracy, with reported sensitivity and specificity of 94%. A single retrospective study showed that in intermediate-to-high pretest probability children, US followed by CT is most cost-effective, whereas, in low pretest probability patients, US alone is the most effective and least costly strategy. If CT is performed, the use of intravenous contrast is recommended; however, the use of enteric contrast, such as oral or rectal contrast, has not been shown to significantly increase sensitivity in children and should be left to the discretion of the individual department and hospital policy. Addition of multiplanar reformats, such as coronal images, has been shown in a small study to increase reader confidence in identifying the appendix in its entirety and other periappendiceal findings and should be included in the CT protocol, particularly, as this does not require additional scanning and increased radiation dose to obtain. Recently, nonvisualization of the appendix on a normal CT has been shown to have a high negative predictive value — 98.7% (95% CI, 95.5%, 99.8%).

Pregnant Patients

Since the last revision of these appropriateness criteria, evaluation of the accuracy of imaging in pregnant women has received more attention in the literature. In general, ionizing radiation from CT should be avoided during pregnancy. US is clearly a safer imaging option and is the first imaging test of choice, although CT after equivocal US has been validated for diagnosis. A systematic literature review through August 2008 addressed eight retrospective studies of CT and MRI after negative or inconclusive US in pregnant women. The pooled sensitivity of CT after US was 86% (95% CI, 64% to 97%), and the specificity was 97% (95% CI, 86% to 100%). MRI is the preferred test after inconclusive US, as new studies have shown a comparable sensitivity and specificity with CT without exposing the fetus to ionizing radiation. The pooled sensitivity of MRI after US was 80% (95% CI, 44% to 98%) and the specificity was 99% (95% CI, 94% to 100%). Although these findings suggest an imaging algorithm of US followed by MRI, if the initial US is inconclusive, the detection of a normal appendix in pregnant patients has been shown to be as low as 2%.

Nuclear Medicine

Nuclear medicine imaging with white blood cell (WBC) scans has also been reported for evaluating right lower quadrant pain. However, the sensitivity and specificity of nuclear scans for this indication have been shown to be significantly inferior to US, CT, and MR.

Summary

• Appendicitis may be diagnosed clinically; however, imaging increases sensitivity and specificity for diagnosis.
• In general, CT is the most accurate imaging study for evaluating suspected appendicitis and alternative etiologies of right lower quadrant abdominal pain.
• In children, US is the preferred initial examination, as it is nearly as accurate as CT for diagnosis of appendicitis without exposure to ionizing radiation.
• In pregnant women, increasing data support the use of MR after equivocal or inconclusive US.

Anticipated Exceptions

Nephrogenic systemic fibrosis (NSF) is a disorder with a scleroderma-like presentation and a spectrum of manifestations that can range from limited clinical sequelae to fatality. It appears to be related to both underlying severe renal dysfunction and the administration of gadolinium-based contrast agents. It has occurred primarily in patients on dialysis, rarely in patients with very limited glomerular filtration rate (GFR) (i.e., <30 mL/min/1.73m²), and almost never in other patients. There is growing literature regarding NSF. Although some controversy and lack of clarity remain, there is a consensus that it is advisable to avoid all gadolinium-based contrast agents in dialysis-dependent patients unless the possible benefits clearly outweigh the risk, and to limit the type and amount in patients with estimated GFR rates <30 mL/min/1.73m². For more information, please see the ACR Manual on Contrast Media (see the "Availability of Companion Documents" field).

Abbreviations

• CT, computed tomography
• MRI, magnetic resonance imaging
• RLQ, right low quadrant
• Tc, technetium
• US, ultrasound
• WBC, white blood cell

Relative Radiation Level Designations

Relative Radiation Level*	Adult Effective Dose Estimate Range	Pediatric Effective Dose Estimate Range
O	0 mSv	0 mSv
	<0.1 mSv	<0.03 mSv
	0.1-1 mSv	0.03-0.3 mSv
	1-10 mSv	0.3-3 mSv
	10-30 mSv	3-10 mSv
	30-100 mSv	10-30 mSv
*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 (e.g., region of the body exposed to ionizing radiation, the imaging guidance that is used). The RRLs for these examinations are designated as NS (not specified).

Algorithms were not developed from criteria guidelines.

The recommendations are based on analysis of the current literature and expert panel consensus.

Selection of appropriate radiologic imaging procedures for evaluation of patients with acute right lower quadrant pain and suspected appendicitis

The American College of Radiology (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 exams generally used for evaluation of the patient's condition are ranked. Other imaging studies necessary to evaluate other co-existent 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 U.S. Food and Drug Administration (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.

An implementation strategy was not provided.

Not applicable: The guideline was not adapted from another source.

The American College of Radiology (ACR) provided the funding and the resources for these ACR Appropriateness Criteria®.

Committee on Appropriateness Criteria, Expert Panel on Gastrointestinal Imaging

Panel Members: Max Paul Rosen, MD, MPH (Panel Chair); Alexander Ding, MD, MS (Research Author); Michael A. Blake, MB, BCh (Panel Vice-Chair); Mark E. Baker, MD; Brooks D. Cash, MD; Jeff L. Fidler, MD; Thomas H. Grant, DO; Frederick L. Greene, MD; Bronwyn Jones, MD; Douglas S. Katz, MD; Tasneem Lalani, MD; Frank H. Miller, MD; William C. Small, MD, PhD; Stephanie Spottswood, MD, MSPH; Gary S. Sudakoff, MD; Mark Tulchinsky, MD; David M. Warshauer, MD; Judy Yee, MD; Brian D. Coley, MD

Not stated

This is the current release of the guideline.

This guideline updates a previous version: Bree RL, Rosen MP, Foley WD, Gay SB, Grant TH, Heiken JP, Huprich JE, Lalani T, Miller FH, Ros PR, Sudakoff GS, Greene FL, Rockey DC, Expert Panel on Gastrointestinal Imaging. ACR Appropriateness Criteria® right lower quadrant pain. [online publication]. Reston (VA): American College of Radiology (ACR); 2007. 5 p. [35 references]

The appropriateness criteria are reviewed biennially and updated by the panels as needed, depending on introduction of new and highly significant scientific evidence.

Electronic copies: Available in Portable Document Format (PDF) from the American College of Radiology (ACR) Web site.

Print copies: Available from the American College of Radiology, 1891 Preston White Drive, Reston, VA 20191. Telephone: (703) 648-8900.

The following are available:

• ACR Appropriateness Criteria®. Overview. Reston (VA): American College of Radiology; 2 p. Electronic copies: Available in Portable Document Format (PDF) from the American College of Radiology (ACR) Web site.
• ACR Appropriateness Criteria®. Literature search process. Reston (VA): American College of Radiology; 1 p. Electronic copies: Available in Portable Document Format (PDF) from the ACR Web site.
• ACR Appropriateness Criteria®. Evidence table development. Reston (VA): American College of Radiology; 4 p. Electronic copies: Available in Portable Document Format (PDF) from the ACR Web site.
• ACR Appropriateness Criteria®. Radiation dose assessment introduction. Reston (VA): American College of Radiology; 2 p. Electronic copies: Available in Portable Document Format (PDF) from the ACR Web site.
• ACR Appropriateness Criteria® Manual on contrast media. Reston (VA): American College of Radiology; 90 p. Electronic copies: Available in PDF from the ACR Web site.

None available

This summary was completed by ECRI on March 19, 2001. The information was verified by the guideline developer on March 29, 2001. This summary was updated by ECRI on March 24, 2006. This summary was updated by ECRI Institute on June 23, 2009. This summary was updated by ECRI Institute on December 1, 2010.

Instructions for downloading, use, and reproduction of the American College of Radiology (ACR) Appropriateness Criteria® may be found on the ACR Web site .