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Acute appendicitis in children: Diagnostic imaging

Acute appendicitis in children: Diagnostic imaging
Authors:
George A Taylor, MD
Mary L Brandt, MD
Monica Esperanza Lopez, MD, MS
Section Editor:
Joshua Nagler, MD, MHPEd
Deputy Editor:
James F Wiley, II, MD, MPH
Literature review current through: Jul 2022. | This topic last updated: Jul 21, 2022.

INTRODUCTION — This topic will review diagnostic imaging for acute appendicitis in children. The epidemiology, clinical features, diagnosis, and treatment of appendicitis in children and the evidence regarding the risk for malignancy associated with ionizing radiation during abdominopelvic CT in children with appendicitis are discussed separately:

(See "Acute appendicitis in children: Clinical manifestations and diagnosis".)

(See "Acute appendicitis in children: Management".)

(See "Radiation-related risks of imaging", section on 'Children and adolescents'.)

IMAGING DECISION — The decision to perform imaging in the diagnostic evaluation of children with abdominal pain is determined by clinical findings and the setting as follows (algorithm 1):

Low clinical likelihood of appendicitis – Imaging is not warranted in most children who are unlikely to have appendicitis based upon the clinical examination and laboratory studies. (See "Acute appendicitis in children: Clinical manifestations and diagnosis", section on 'Clinical suspicion'.)

Incomplete or equivocal findings for appendicitis For children who have atypical or equivocal findings for appendicitis on physical examination and laboratory testing, imaging may be helpful to establish or exclude the diagnosis. Imaging may also be needed for patients who have received antibiotics prior to evaluation. Ultrasonography (US) and computed tomography (CT), separately or in combination, are the modalities used most frequently although magnetic resonance imaging (MRI) has similar diagnostic accuracy as CT. (See 'Imaging approach' below and "Acute appendicitis in children: Clinical manifestations and diagnosis", section on 'Clinical suspicion'.)

High clinical likelihood of appendicitis – We suggest that children with a high likelihood of appendicitis based upon clinical findings undergo evaluation by a surgeon with pediatric expertise prior to any imaging study other than US. (See "Acute appendicitis in children: Clinical manifestations and diagnosis", section on 'Clinical suspicion'.)

Limited pediatric capability – In settings where operative care for children with appendicitis is not available, resources for appropriate pediatric imaging and interpretation of radiographic findings may also be lacking [1]. Clinicians managing patients with suspected appendicitis in these settings, whenever possible, should contact a pediatric surgeon prior to imaging or treatment. In general, CT should be avoided prior to transfer.

A systematic institutional approach to the choice of imaging is associated with improved outcomes including increased diagnosis of appendicitis at initial presentation, reduced radiation exposure, decreased negative appendectomy rate, and no increase in perforation rate. (See 'Clinical protocols' below.)

Clinical scoring systems have the potential to help with decisions regarding diagnostic imaging and limit the use of imaging in children with a low risk of appendicitis. (See "Acute appendicitis in children: Clinical manifestations and diagnosis", section on 'Clinical scoring systems'.)

IMAGING APPROACH — We and the American College of Radiology recommend that imaging in children with atypical or equivocal clinical findings for appendicitis begin with ultrasonography (US) in order to avoid unnecessary radiation [2].

If the appendix is not visualized or the findings on US are otherwise not diagnostic, the patient may be observed with serial physical examinations and repeated imaging (US, CT, or MRI) performed at a later time if a clinical diagnosis of appendicitis cannot be made and concerning symptoms persist. If a clinical diagnosis of appendicitis cannot be made or, if more prompt diagnosis is desired, the patient may directly proceed to contrast-enhanced CT or MRI. (See 'Techniques' below and 'Magnetic resonance imaging' below.)

In patients whose initial ultrasound is equivocal for the diagnosis of appendicitis, repeat physical examination and a second ultrasound in patients who have persistent findings of appendicitis has good diagnostic accuracy and can markedly reduce the number of children undergoing CT. As an example, in a prospective observational study of 294 children undergoing acute evaluation for abdominal pain (38 percent with appendicitis), a pathway that utilized serial physical examination, surgical consultation, and repeat ultrasound for patients whose initial ultrasound was equivocal; discharge for patients whose initial ultrasound showed a normal appendix, and surgical consultation for patients with initial ultrasounds that were positive for appendicitis achieved a sensitivity of 97 percent and a specificity of 91 percent [3]. CT was performed in four patients.

Use of MRI instead of CT is limited to pediatric specialty centers because of issues related to cost, availability, limited experience with interpretation, and the potential need for sedation in younger children. In settings with adequate experience in interpreting MRI for the presence of appendicitis and with the resources to rapidly obtain and interpret the study, MRI may be preferable to CT. Evidence suggests that the use of MRI is associated with similar diagnostic accuracy and negative appendectomy rates. (See 'Magnetic resonance imaging' below.)

Ultrasound for initial diagnostic imaging in obese children may avoid the need for CT in a large proportion of these patients. As an example, in a small observational study that evaluated outcomes for 76 obese children undergoing US for suspected appendicitis, appendicitis was confirmed by US alone in 23 of 26 patients and was excluded in 42 of 50 patients without the use of CT imaging [4]. However, given the technical limitations of ultrasound in diagnosing appendicitis in very obese children, some clinicians may choose to perform contrast CT or MRI as the initial imaging strategy in these patients. If a CT is performed, we use intravenous (IV) contrast alone and begin the evaluation with a focused examination and expand the study to include the entire abdomen if an abnormality is seen on the uppermost image. When reviewing the images, coronal reformatted images increase the level of confidence in identification of the normal and abnormal appendix [5]. (See 'Contrast' below and 'Focused CT' below.)

In the United States, increased use of ultrasound alone or ultrasound with CT in children’s hospitals has been associated with lower rates of negative appendectomy without an increase in appendiceal rupture or patients returning with a new diagnosis of appendicitis within two weeks of initial emergency department visit [6-9].

ULTRASONOGRAPHY — Ultrasonography (US) is available in most institutions, is relatively inexpensive, and avoids unnecessary radiation [10]. It has the added advantage of identifying ovarian pathology, such as torsion or an ovarian cyst. However, accuracy depends upon the skill and experience of the sonographer.

Test performance — US improves diagnostic accuracy in selected children with suspected appendicitis [11]. In pediatric patients, overall sensitivities of US performed by pediatric US technicians and/or pediatric radiologists for appendicitis, including studies in which the appendix was not visualized, have varied from 74 to 100 percent and specificities have ranged from 88 to 99 percent [11-19]. Factors that increase the diagnostic accuracy of US in children include operator experience [12], longer duration of abdominal pain [20], and incorporation of specific thresholds for white blood cell count and proportion of polymorphonuclear cells [21] or white blood cell count alone [22].

Evidence also suggests that emergency physicians with proper training and experience in performing bedside US for appendicitis can achieve reasonable diagnostic accuracy in children. For example, in a meta-analysis of 21 studies, the pooled sensitivity and specificity for pediatric examinations was 89 to 96 percent and 92 to 97 percent, respectively [23]. However, the accuracy of bedside US for appendicitis in children is operator dependent and requires a rigorous scanning protocol that results in consistent visualization of the appendix and an ongoing quality-review process that includes saving the images in the patient record for review and comparison with subsequent examinations.

Test performance for ultrasonography (US) also varies by whether the appendix is visualized and patient body habitus:

Appendix visualized – When the appendix is visualized the diagnostic accuracy of US is equivalent to CT [24]. As an example, in a multicenter study of 965 children undergoing abdominal US for possible appendicitis, sensitivity and specificity were 98 and 92 percent, respectively, in the 469 patients in whom the appendix was clearly seen [12].

Appendix not visualized – The diagnosis of appendicitis cannot be reliably excluded by US unless a normal appendix is seen. Reported appendix visualization during pediatric ultrasonography vary from 22 to 98 percent of examinations [13,14,25]. Factors that affect this variability primarily include the experience and technique of the sonographer, as well as the child’s body habitus.

In these patients, the likelihood of appendicitis is not trivial and clinical findings should be used to determine further care. For example, in one retrospective observational study of almost 490 children with suspected appendicitis with no appendix visualized on US, 7 percent were diagnosed with appendicitis [26]. In females with a negative or equivocal right lower quadrant (RLQ) ultrasound, a pelvic ultrasound should also be performed to identify any ovarian pathology, such as torsion or an ovarian cyst.

On the other hand, non-visualization of the appendix with secondary signs indicative of appendicitis may still provide diagnostic support. For example, in a review of 3750 US exams of which only 4.3 percent were deemed equivocal based on a six-point risk-stratified scoring system, the additional findings of loss of mural stratification, peri-appendiceal fat inflammation, and presence of an appendicolith were significant predictors of appendicitis in children with otherwise equivocal exams [27].

High body mass index (BMI) – In children with a high BMI or in whom the likelihood of appendicitis based upon clinical findings is low, US can result in a significant number of false-positive and false-negative results. For example, in an observational study of 263 children, 4 to 17 years of age, with suspected appendicitis, US was inaccurate in 101 examinations (88 false-positive findings, 13 false-negative findings) [28]. Inaccurate examinations were significantly associated with high BMI (≥85th percentile, primarily false-negative results) or low pretest clinical suspicion for appendicitis (odds ratio [OR] 2.0, 95% CI 1.1-3.5 and OR 2.4, 95% CI 1.4-4.0, respectively, primarily false-positive results). (See 'Pitfalls and limitations of US' below.)

Techniques — The following techniques may improve visualization of the appendix and permit more accurate diagnosis of appendicitis:

Posterior compression – The addition of posterior manual compression to graded compression can help to identify the appendix. This was demonstrated in a report of 570 consecutive patients referred for suspected appendicitis, 28 percent of whom were less than 16 years of age [29]. Visualization of the appendix increased from 85 to 95 percent with posterior manual compression.

Positional scanning – Scanning in the flank and pelvis, in addition to the right lower quadrant, may be useful. Among 199 children with appendicitis, scanning of the retrocecal area using a posterolateral approach, followed by scanning of the pelvis through a full urinary bladder, and scanning of the right lower quadrant resulted in identification of 68 percent of abnormal appendices [14]. The combination of noncompressive and compressive techniques increased the identification rate to 96 percent.

Pitfalls and limitations of US — There are a number of difficulties with the use of US for the diagnosis of acute appendicitis.

Fat absorbs and diffuses the US beam making it more difficult to scan overweight children.

It can be difficult to identify a normal appendix or one that is only focally inflamed ("tip" appendicitis). Therefore, a negative US examination in the presence of persistent symptoms is not sufficient to reliably exclude appendicitis.

Pain and/or anxiety may make sonographic imaging of the abdomen difficult or impossible in some children.

Many institutions have limited or no access to staff trained to perform US in children during all hours of operation.

Sonographic findings — US findings that support the diagnosis of appendicitis include the following (table 1):

Noncompressible tubular structure in right lower quadrant (image 1)

Wall thickness of the appendix greater than 2 mm (image 2)

Overall diameter greater than 6 mm (image 1)

Hyperemia (image 1)

Free fluid in the right lower quadrant

Thickening of the mesentery

Localized tenderness with graded compression

Presence of a calcified appendicolith (fecalith) (image 1)

A small number of children with a normal appendix visualized on US may have early, or tip, appendicitis. How often this occurs is unknown. Consequently, clinical correlation, observation, and serial examination for 12 to 24 hours with repeated US imaging or performance of enhanced CT or MRI may be required to exclude the diagnosis of appendicitis, even with a normal US examination.

Diagnoses that can mimic appendicitis on US include lymphoma, Crohn disease, and cystic fibrosis [30]. In cystic fibrosis, the appendix may be markedly dilated with thickened secretions, leading to an inaccurate diagnosis of appendicitis.

In addition, we have seen some false-positive US reports where the diagnosis of appendicitis was based upon increased appendiceal wall thickness alone. We recommend caution in utilizing US reports as the sole criterion for diagnosis of appendicitis without other supportive clinical findings.

However, the value of standardized US reporting templates when adopted as part of the implementation of a clinical pathway for pediatric acute appendicitis has been demonstrated by many studies using a multidisciplinary approach and quality-improvement methods; utilization of such standardized reporting systems can reduce the use of CT scans and their associated radiation exposure [31,32] and decrease annual imaging costs [33] while preserving diagnostic performance and important balance metrics, such as negative appendectomy rates [19,34]. Adding posterior manual compression to graded compression [29] and scanning the flank and pelvis [14] may also improve the diagnostic accuracy of US for appendicitis.

In our practice, visualization of a normal appendix constitutes a normal US examination. When the appendix is not visualized in an otherwise unremarkable pelvic examination, we report the study as showing no evidence of appendicitis. In one retrospective observational study of almost 490 children with suspected appendicitis but no appendix visualized on US, 7 percent were diagnosed with appendicitis [26]. Predictors for appendicitis in this study included right lower quadrant inflammatory changes, elevated white blood cell count or C-reactive protein, and duration of abdominal pain for less than three days. In some settings, non-visualization of the appendix with secondary signs suggestive of appendicitis is an infrequently encountered US finding. In a review of 3750 US exams of which only 4.3 percent were deemed equivocal based on a six-point risk-stratified scoring system, the additional findings of loss of mural stratification, peri-appendiceal fat inflammation, and presence of an appendicolith were significant predictors of appendicitis in children with otherwise equivocal exams [27].

Further imaging is determined by the requesting clinician. If further imaging is desired, we typically perform contrast enhanced CT. In other institutions, MRI without contrast may be substituted for CT. (See 'Magnetic resonance imaging' below.)

COMPUTED TOMOGRAPHY — Enhanced CT is a commonly used imaging modality for testing of children with possible appendicitis who have nondiagnostic findings on ultrasound (US) although MRI is used in some institutions instead of CT in older children (eg, older than six years of age) who can cooperate with the examination. (See 'Magnetic resonance imaging' below.)

CT is typically more available and less operator dependent than US but has the disadvantage of exposure to radiation (see "Radiation-related risks of imaging", section on 'Children and adolescents'). CT is also useful in establishing alternative diagnoses for abdominal pain. As an example, in one observational study of 125 children examined with focused CT that was negative for possible appendicitis, 62 had alternative diagnoses made including ileitis or colitis suggestive of inflammatory bowel disease, mesenteric adenitis, and intact or ruptured ovarian cyst [35].

Test performance — In children, sensitivity for the diagnosis of acute appendicitis by CT is 94 to 100 percent, and specificity is 93 to 100 percent [13,17,20,35-37]. Reported specificity is 93 to 100 percent. In one large observational study of 1810 children with suspected appendicitis, CT had high sensitivity and specificity regardless of the duration of abdominal pain [20].

CT has the disadvantage of exposure to ionizing radiation [38-41]. In addition, some children have a paucity of mesenteric fat, which makes visualization of either a normal or an inflamed appendix more difficult, especially on an unenhanced CT [42].

Increased utilization of CT and improved accuracy of imaging for acute appendicitis have not contributed substantially to lower rates of negative appendectomy since the mid-1990s, and the perforation rate remains as high as 33 percent [43,44]. This finding has raised concerns regarding increased exposure to ionizing radiation, healthcare costs, and delay in surgical treatment [38,39,45,46]. Limited evidence suggests that protocols emphasizing early surgical evaluation, selective imaging that emphasizes US, and careful serial examination for patients with equivocal radiographic and/or clinical findings can achieve lower rates for negative appendectomy and perforation [45,47-49]. (See 'Clinical protocols' below.)

The benefit of CT for appendicitis in children may also vary according to patient age and sex. As an example, in a multicenter observational study of 55,227 children undergoing appendectomy, children younger than five years of age who underwent CT had a clinically significant reduction in the negative appendectomy rate (NAR) when compared to children who did not receive a CT (NAR 5 versus 22 percent, respectively, for males [OR 0.18], NAR 2 versus 18 percent, respectively, for females [OR 0.11]) [50]. Among males five years of age and older who underwent appendectomy, the NAR was 1 percent and was not significantly different for those males who had advanced diagnostic imaging (US, CT, or both). Diagnostic imaging also did not greatly impact the NAR in females, although females older than 10 years of age had a higher NAR than either males or females 5 to 10 years old. Thus, CT was associated with the greatest reduction in the NAR among young children (<5 years of age).

Techniques — Techniques to improve the accuracy and safety of CT include the use of intravenous (IV) contrast, limiting the examination to a focused CT of the pelvic contents, and adjusting scanning parameters to achieve the lowest radiation dose possible while maintaining diagnostic accuracy. Enteral contrast (rectal or oral) does not appear to improve diagnostic imaging over the use of IV contrast alone.

Contrast — We recommend that children with suspected appendicitis and nondiagnostic findings on US who proceed directly to CT undergo contrast-enhanced CT with IV contrast rather than no contrast. In addition, we recommend that children with suspected appendicitis undergo contrast-enhanced CT with IV contrast alone rather than IV contrast combined with enteral (oral or rectal) contrast.

IV contrast is helpful in identifying the appendix and adjacent structures, particularly in children under the age of 10 years who generally have limited mesenteric fat. For example, in 306 children with suspected appendicitis who underwent both unenhanced helical CT of the lower abdomen and IV contrast-enhanced CT of the entire abdomen, contrast-enhanced CT had a significantly higher pooled sensitivity for appendicitis than unenhanced CT (90 versus 66 percent, respectively) with similar specificity (94 versus 96 percent, respectively) [51]. (See 'Test performance' above.)

In addition, if a child with suspected appendicitis has equivocal or negative findings on an unenhanced CT, then frequently the study is repeated with contrast, thus increasing radiation exposure.

Contrast has also been given enterally (rectal or oral), to opacify and distend the cecum in an attempt to improve visualization of the inflamed appendiceal wall or mesentery [13,37,52]. However, observational studies suggest that rectal or oral contrast does not further improve test performance over IV contrast CT alone [53-55]. (See 'Test performance' above.)

Furthermore, enteral contrast administration presents several challenges. Rectal contrast administration is uncomfortable, difficult to administer in patients with diarrhea, and contraindicated in patients with intestinal perforation. Oral contrast delays scanning for approximately two hours, does not appear in the terminal ileum in up to 30 percent of patients at the time of CT scan, and may require nasogastric tube placement for proper administration [54].

IV contrast can cause hypersensitivity reactions, chemotoxicity, and renal failure. However, these reactions are rare in children. The risk of contrast-induced immediate hypersensitivity can be reduced by using low osmolal contrast material agents (eg, iodixanol [Visipaque]) and in children with asthma, ensuring control of symptoms before the procedure. (See "Patient evaluation prior to oral or iodinated intravenous contrast for computed tomography", section on 'Patients with past reactions to contrast'.)

Focused CT — A CT scan limited to the lower abdomen may be sufficient to diagnose appendicitis, while exposing the child to less radiation. Some experts advocate scanning from the bottom of the third lumbar vertebral body to the pubic ramus. The scan can be expanded to include the upper abdomen if an abnormality is found on the initial uppermost image [56].

Support for this approach was demonstrated in a retrospective review of 93 abdominal CT scans obtained with oral and IV contrast in children with suspected appendicitis [57]. All of the abnormal findings leading to a diagnosis of appendicitis were located below the lower pole of the right kidney (RLP). In addition, there was no difference between the sensitivity and specificity for CT of the entire abdomen compared with CT below the RLP.

CT scanning parameters — CT scanning parameters, such as the tube current setting (in milliamperes) and pitch (table speed), should be adjusted based upon patient weight or girth to reduce radiation dose [41,58-61]. Weight-based reductions in tube current have been recommended [62]. Radiation dose can also be significantly reduced by increasing pitch. In addition, iterative reconstruction techniques have been shown to reduce radiation dosage by 45 to 46 percent compared with traditional weight-based protocols while maintaining diagnostic accuracy [63].

Awareness of these recommendations may not be widespread, however. One report described the scanning parameters used for body CT examinations that had been obtained at referring hospitals and were then sent to a children's hospital for further review [64]. Mean tube current settings exceeded weight-based recommendations in all age groups, and 53 percent of studies were performed without an adjustment in pitch.

Important information on opportunities to reduce radiation dose during CT imaging in children can be found on the "Image Gently" website [65].

Pitfalls and limitations of CT — There are several limitations to the use of CT for the diagnosis of appendicitis [52].

Scanning performed in institutions not familiar with pediatric protocols may result in excessive radiation. (See 'CT scanning parameters' above.)

A normal appendix is more difficult to visualize in children with less intraperitoneal fat.

A fluid-filled loop of small bowel may be misinterpreted as an inflamed appendix.

An appendicolith can be obscured by intestinal contrast.

A Meckel's diverticulum can be misinterpreted as an enlarged appendix.

CT findings — The diagnosis of appendicitis is unlikely if the appendix is not identified as a separate structure on CT and there are no additional signs of inflammation in surrounding structures. When multiplanar reformations are performed, the appendix is frequently best visualized in the coronal plane [55].

Findings on CT that support the diagnosis of appendicitis include (image 3 and table 2):

Wall thickness greater than 2 mm

Appendicolith (fecalith) (image 4 and image 5)

Enlargement of the appendix (image 6)

Concentric thickening of the appendiceal wall (target sign)

Phlegmon

Abscess (image 6)

Free fluid

Thickening of the mesentery, fat stranding

Other pathological processes that involve the appendix and can look like acute appendicitis on imaging studies include the following:

Crohn's disease and lymphoma may be indistinguishable from appendicitis on CT.

Patients with cystic fibrosis may have a markedly enlarged appendix filled with mucus or stool without acute appendicitis.

MAGNETIC RESONANCE IMAGING — In settings with adequate experience in interpreting MRI for the presence of appendicitis and with the resources to rapidly obtain and interpret the study, MRI may be preferable to CT when results of abdominal ultrasound (US) are not diagnostic. However, like CT, MRI is not always definitive. Clinicians must apply clinical correlation to imaging results. The advantages of MRI as a primary modality for evaluating pediatric appendicitis such as lack of ionizing radiation and no need for contrast are balanced by barriers such as its limited availability, expertise necessary to properly interpret, and higher cost. Local decisions about the best imaging modality selection for appendicitis should be based on the center's resources and pediatric radiology capabilities.

Evidence suggests that MRI without contrast can provide similar diagnostic accuracy as CT without radiation exposure or excessive time delay (image 7). For example, in a meta-analysis of eight studies that evaluated diagnostic accuracy of MRI for appendicitis in children, the pooled sensitivity was 96 percent (95% CI 95- 97 percent), and the pooled specificity was 96 percent (95% CI 94- 98 percent) [66]. Two additional meta-analyses had similar findings [67,68]. Reported techniques included MRI without contrast using four-sequence axial and coronal T2 and coronal inversion recovery sequences [69] and contrast-enhanced MRI [70]. In three of the studies included in the meta-analysis, imaging time was reported with median or mean imaging times <20 minutes [69-71]. In one of these studies, total median time from request to radiology report was 123 minutes [69]. In a single-center, retrospective review of over 400 children who underwent unenhanced MRI as the initial imaging modality for appendicitis (not included in the meta-analysis), the sensitivity, specificity, and accuracy of MRI were 97.9, 99, and 98.8 percent, respectively; an alternate diagnosis was identified in 37 percent of patients who had negative results for appendicitis, and only 3 percent of patients required sedation for the study [72].

In another retrospective study not included in the meta-analysis and analyzing 662 children older than six years of age who were evaluated for abdominal pain before and after the adoption of a new imaging algorithm for appendicitis, US followed by MRI for patients with nondiagnostic US results had a sensitivity of 100 percent and a specificity of 99 percent in 397 patients (prevalence of appendicitis 41 percent), which was similar to the findings in the 265 patients who had oral and IV contrast CT as the primary mode of imaging [47]. Negative appendectomy rates were low in both groups (1.4 to 2.5 percent). Time to antibiotics or operation was not different between the groups. However, the time to definitive imaging (CT or MRI) was long for both modalities (7 to 11 hours for CT and 9 to 13 hours for MRI). Since the publication of this study, most centers have adopted shorter imaging protocols with fewer sequences.

PLAIN RADIOGRAPHS — Plain radiographs of the abdomen are primarily indicated in children with suspected appendicitis to confirm a clinical suspicion of bowel obstruction or perforation [73]. Otherwise, plain films are of little value and should not be routinely performed. Plain films may occasionally show secondary signs in acute appendicitis, such as a fecalith, or suggest an alternative diagnosis, such as basilar pneumonia (table 3).

CLINICAL PROTOCOLS — Institutions should develop imaging protocols that they can utilize effectively. Both ultrasonography (US) and CT are valuable modalities for imaging in children with suspected appendicitis. Evidence also suggests a role for MRI in patients who can cooperate with the study [69]. The choice of study in any given clinical situation depends upon patient characteristics, such as obesity and sex, and institutional resources, such as the availability of US, CT, or MRI and the expertise of the staff [56]. Of note, clinicians may be reluctant to use a protocol that includes modalities that are frequently unavailable or cannot be interpreted with confidence.

Imaging protocols for the diagnosis of appendicitis in children can result in a significant decrease in radiation exposure without sacrificing diagnostic accuracy or clinical outcomes. We therefore endorse developing imaging protocols to streamline decision-making, improve safety, and decrease cost for all institutions evaluating children with suspected appendicitis. US should be the primary modality for children with appendicitis. For facilities without US capabilities, conversation with pediatric colleagues should precede any decision about imaging.

Observational studies that have evaluated outcomes before and after implementation of imaging protocols show decreased CT utilization of approximately 50 to 60 percent [74-76]. These protocols emphasize the use of clinical scoring systems, US as the initial diagnostic imaging test, and/or clinical evaluation by a surgeon to guide patient management decisions. Sensitivity and specificity for the diagnosis of appendicitis was high in two of these studies (sensitivity 98.6 to 99 percent, specificity 91 to 94 percent) without an increase in negative appendectomies [74,76]. In one study, missed appendicitis after protocol implementation was 0.5 percent [74]. When MRI was used instead of CT, sensitivity and specificity was also high (100 percent and 99 percent, respectively) with a negative appendectomy rate of 1.5 percent [47].

However, even in settings where multidisciplinary protocols have been developed, achieving high rates of compliance can be difficult. For example, in two of the above studies, adherence to the protocol ranged from approximately 46 to 57 percent [74,76].

The risk of cancer following ionizing radiation during abdominopelvic CT in children with appendicitis is discussed separately. (See "Radiation-related risks of imaging", section on 'Children and adolescents'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Appendicitis in children".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

Basics topics (see "Patient education: Appendicitis in adults (The Basics)" and "Patient education: Appendicitis in children (The Basics)")

SUMMARY AND RECOMMENDATIONS

The decision to perform imaging in the diagnostic evaluation of children with abdominal pain is determined by clinical findings and the setting (see 'Imaging decision' above):

Atypical or equivocal findings – Imaging can assist in the evaluation of children with atypical or equivocal clinical findings for appendicitis (algorithm 1).

Low likelihood of appendicitis – Children with clinical findings that do not suggest appendicitis should not undergo imaging.

High likelihood of appendicitis – We suggest that children with a high likelihood of appendicitis based upon clinical findings undergo evaluation by a surgeon with pediatric expertise prior to urgent imaging studies.

Facilities with limited pediatric imaging capability – In settings where pediatric resources to perform and interpret imaging is not available, transfer of children with possible appendicitis to a center with pediatric radiology and pediatric general surgery capabilities should occur whenever possible. (See 'Imaging decision' above and "Acute appendicitis in children: Clinical manifestations and diagnosis", section on 'Imaging'.)

Imaging approach – We and the American College of Radiology recommend that imaging in children with atypical or equivocal clinical findings for appendicitis begin with ultrasonography (US). US findings that support the diagnosis of appendicitis are summarized in the table (table 1 and image 1). (See 'Sonographic findings' above.)

Ultrasonography – US is particularly useful in peri- and postpubertal females to identify alternative gynecologic diagnoses, such as ovarian cyst or ovarian torsion. It is less reliable in obese children because fat absorbs and diffuses the US beam. (See 'Ultrasonography' above.)

A normal appendix must be seen on US in order to reliably exclude appendicitis in a patient with persistent symptoms. If the appendix is not visualized or the findings on US are otherwise not diagnostic, options include (see 'Imaging approach' above):

Observation with serial physical examinations and repeated imaging (US, contrast-enhanced computed tomography [CT], or magnetic resonance imaging [MRI]) performed at a later time if a clinical diagnosis of appendicitis cannot be made.

The patient may directly proceed to contrast-enhanced CT or MRI if a more prompt diagnosis is desired.

Computed tomography – If CT is performed, we recommend that children undergo contrast-enhanced CT with intravenous (IV) contrast rather than no contrast. In addition, we suggest that these children undergo contrast-enhanced CT with IV contrast alone rather than IV contrast combined with enteral (oral or rectal) contrast. (See 'Contrast' above.)

When using CT in children with possible appendicitis, we recommend that radiation doses be adjusted as much as possible without compromising the accuracy of the study. (See 'Focused CT' above and 'CT scanning parameters' above.)

Magnetic resonance imaging – MRI with or without contrast can provide similar diagnostic accuracy as CT without radiation exposure or excessive time delay (image 7) and may be preferred in settings with adequate experience in interpreting MRI for the presence of appendicitis and with the resources to rapidly obtain and interpret the study. (See 'Magnetic resonance imaging' above.)

Plain radiographs – Plain radiographs of the abdomen are primarily indicated in children with suspected appendicitis to confirm a clinical suspicion of bowel obstruction or perforation. Otherwise, plain films are of little value and should not be routinely performed. (See 'Plain radiographs' above.)

Clinical protocols – Institutions should develop imaging protocols that they can utilize effectively. Such protocols have been associated with increased diagnosis of appendicitis at initial presentation, reduced radiation exposure, decreased negative appendectomy rate, and no increase in perforation rate. (See 'Clinical protocols' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges David E Wesson, MD, who contributed to earlier versions of this topic review.

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Topic 6478 Version 55.0

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