Sonography as the First Line of Evaluation in Children With Suspected Acute Appendicitis

cute appendicitis is the most common cause of abdominalpain requiring urgent surgery in children and is a true gas-trointestinal emergency.1 The diagnosis is suspected and

made primarily on the basis of clinical findings. Classically, theseclinical findings consist of periumbilical pain migrating to the rightlower quadrant, accompanied by fever and leukocytosis. However,the classic signs are not always present, and symptoms can benonspecific and overlap with other causes of abdominal pain. The clinical presentation is also complicated in young children bytheir limited communication skills.

Historically, computed tomography (CT) has been the firstchoice of imaging in acute abdominal pain, with sensitivity of up to96% and specificity of up to 97%.2–5 However, because of theincreasing awareness of the radiation dose imparted to patients byCT and the theoretical increased risk of cancer that it causes,6 thereis a nationwide campaign to reduce the radiation from diagnosticimaging in children (Image Gently).7 Sonography uses sound wavesinstead of ionizing radiation to evaluate for disease and in some stud-ies has demonstrated accuracy similar to that of CT.5,8 Therefore,sonography should be used as the primary diagnostic modality inthe evaluation of suspected acute appendicitis in children.

Sonography is widely available, can be performed at the bed-side, involves a short acquisition time, does not use ionizing radia-tion, is relatively inexpensive, and may show evidence of othercauses of abdominal pain. It is particularly useful in evaluating youngwomen, in whom the radiation dose to the reproductive organsshould be minimized and for whom it is important to exclude ovar-ian and uterine conditions that might mimic appendicitis. Therehave been multiple studies evaluating the value of sonography inthe evaluation of appendicitis, showing varying sensitivity, speci-ficity, and accuracy. However, a recent study by Pacharn et al9 foundthat sonography for acute appendicitis had a negative predictivevalue of 95%, making it an excellent screening tool in the evaluationof acute appendicitis. Goldin et al1 suggested that standardizing thetechnique and criteria will decrease variability in the diagnostic accu-racy of sonography across institutions.

Leann E. Linam, MD, Martha Munden, MD

Received May 14, 2012, from Arkansas Children’sHospital, University of Arkansas for MedicalSciences, Little Rock, Arkansas USA (L.E.L.); andTexas Children’s Hospital, Houston, Texas USA(M.M.). Revision requested May 22, 2012.Revised manuscript accepted for publication June6, 2012.

Address correspondence to Leann E. Linam,MD, Department of Radiology, ArkansasChildren's Hospital, University of Arkansas forMedical Sciences, Slot 105, 1 Children’s Way,Little Rock, AR 72202-3500 USA.

E-mail: llinam@uams.edu

AbbreviationsCT, computed tomography

A

©2012 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2012; 31:1153–1157 | 0278-4297 | www.aium.org

SOUND JUDGMENT SERIES

Invited paper

The Sound Judgment Series consists ofinvited articles highlighting the clinicalvalue of using ultrasound first in specificclinical diagnoses where ultrasound hasshown comparative or superior value. Theseries is meant to serve as an educationaltool for medical and sonography studentsand clinical practitioners and may helpintegrate ultrasound into clinical practice.

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Technique

The standard sonographic evaluation of the abdomen basedon the American Institute of Ultrasound in Medicine prac-tice guideline10 includes imaging of the appendix. A com-plete abdominal sonographic examination does not needto be performed in the evaluation of acute appendicitis.However, because the appendix is not always located in theright lower quadrant and an abscess could be present, imag-ing should include not only the right lower quadrant butalso the pelvis and left lower quadrant. A survey of theabdomen for free fluid or bowel thickening elsewhere is alsohelpful, especially in cases of suspected perforation.

At the start of the examination, it is helpful to ask thepatient to point to the site of maximal tenderness and beginscanning in this location. Using a high-resolution lineartransducer, the abdomen should be compressed while scan-ning, which moves bowel gas out of the field of view.11 Thiscompression sonography is performed with an empty blad-der. The most reliable way to identify the appendix is to findthe ascending colon, follow the colon proximally to thececum, and then find the appendix extending off the cecum.

Linam and Munden—Sonography in Children With Suspected Acute Appendicitis

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Figure 1. A, Longitudinal image of the right lower quadrant showing a nor-

mal appendix. The maximal outer wall diameters are 5.3 and 5.7 mm. Less

than 6 mm is considered normal. B, Transverse images of the right lower

quadrant. The image on the left shows a normal appendix (arrows). The

image on the right is with compression; the appendix compresses (arrow).

A

B

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If the appendix cannot be seen in the supine position, it maybe helpful to place the patient in the left lateral decubitusposition to cause a retrocecal appendix to be better seen.Scanning with a full bladder may also be helpful because itcan better delineate a deep pelvic appendix that might beobscured by overlying bowel.

The complete appendix should be visualized, includingthe tip. The maximal outer wall diameter should be meas-ured, and the wall thickness should be measured along thecourse of the appendix. The normal maximal outer walldiameter of the appendix is less than 6 mm, and the muralthickness is less than 2 mm (Figure 1A). Compression ofthe appendix should be performed, with documentation ofthe appearance of the appendix during compression. A nor-mal appendix compresses (Figure 1B). Secondary signssuch as free fluid, a fecalith, and hyperechoic surrounding fatshould be documented. Doppler imaging is helpful to eval-uate for hyperemia; however, a necrotic appendix will havedecreased or no blood flow. Video clips should be obtainedto show normal peristalsis unless the physician is presentduring the scan. If an abscess is suspected, a lower- frequencycurved array transducer may be used for a larger field of viewand deeper penetration.

It is not always necessary to identify a normal appen-dix to consider the findings negative.9 If there are no sec-ondary signs as mentioned above, and clinical suspicion ismoderately low for appendicitis, many institutions stop theevaluation and consider the sonographic findings negativefor appendicitis.

In the setting of acute appendicitis, the appendix isnoncompressible, and the maximal outer wall diameter isgreater than 6 mm (Figure 2). An appendicolith may bepresent, helping the diagnosis (Figure 3); however, anappendicolith can be present without acute appendicitis,and the presence of an appendicolith does not confirmacute appendicitis. There may also be secondary signs ofinflammation, such as hyperechoic surrounding fat, freefluid, or an abscess (Figure 4). The wall may be hyperemic(Figure 5). Enlarged nodes can also be seen in the rightlower quadrant, but this finding is nonspecific and can alsobe seen in patients without appendicitis. The surround-ing bowel may be dilated with loss of normal peristalsisdue to ileus.

Conclusions

Right lower quadrant sonography, when performed usingrigorous technique and criteria for diagnosis, is an excel-lent screening tool for acute appendicitis. This examina-tion is quick and painless and does not involve the use ofionizing radiation. Although the sensitivity, specificity, andaccuracy of sonography vary greatly in studies evaluatingthe imaging diagnosis of acute appendicitis, it should bethe first imaging modality when there is clinical concernfor acute appendicitis. Only if the examination is equivocalor if the appendix cannot be identified should other imag-ing modalities such as CT be considered.

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Linam and Munden—Sonography in Children With Suspected Acute Appendicitis

Figure 2. Longitudinal images of the right lower quadrant. The image on the left shows a dilated, thickened appendix. The maximal outer wall diam-

eter of this appendix is 6.6 mm. The image on the right is with compression; there is no change in the appearance of the appendix.

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Linam and Munden—Sonography in Children With Suspected Acute Appendicitis

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Figure 3. Longitudinal image of the right lower quadrant showing an

echogenic shadowing structure within a dilated appendix. It is an

appendicolith associated with appendicitis.

Figure 4. Secondary signs of appendicitis. A, The fat surrounding this

dilated tubular structure is echogenic (asterisks). This appearance is

due to edema in the fat surrounding the appendix. B, Free fluid (arrow).

C, Abscess appearing as a debris-filled fluid collection (asterisk) with

surrounding echogenic fat.

B

CA

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References

1. Goldin AB, Khanna P, Thapa M, McBroom JA, Garrison MM, Parisi MT.Revised ultrasound criteria for appendicitis in children improve diagnosticaccuracy. Pediatr Radiol 2011; 41:993–999.

2. Kaiser S, Frenckner B, Jorulf HK. Suspected appendicitis in children: USand CT—a prospective randomized study. Radiology 2002; 223:633–638.

3. Johansson EP, Rydh A, Riklund KA. Ultrasound, computed tomography,and laboratory findings in the diagnosis of appendicitis. Acta Radiol 2007;48:267–273.

4. Doria AS, Moineddin R, Kellenberger CJ, et al. US or CT for diagnosis ofappendicitis in children and adults? A meta-analysis. Radiology 2006;241:83–94.

5. Poortman P, Lohle PN, Schoemaker CM, et al. Comparison of CT andsonography in the diagnosis of acute appendicitis: a blinded prospectivestudy. AJR Am J Roentgenol 2003; 181:1355–1359.

6. Brenner DJ, Hall EJ. Computed tomography: an increasing source ofradiation exposure. N Engl J Med 2007; 357:2277–2284.

7. Goske MJ, Applegate KE, Boylan J, et al. The “Image Gently” campaign: increasing CT radiation dose awareness through a national education andawareness program. Pediatr Radiol 2008; 38:265–269.

8. Keyzer C, Zalcman M, De Maertelaer V, et al. Comparison of US andunenhanced multi-detector row CT in patients suspected of having acuteappendicitis. Radiology 2005; 236:527–534.

9. Pacharn P, Ying J, Linam LE, Brody AS, Babcock DS. Sonography in theevaluation of acute appendicitis: are negative sonographic findings goodenough? J Ultrasound Med 2010; 29:1749–1755.

10. American Institute of Ultrasound in Medicine. AIUM practice guideline forthe performance of an ultrasound examination of the abdomen and/orretroperitoneum. J Ultrasound Med 2008; 27:319–326.

11. Puylaert JB. Acute appendicitis: US evaluation using graded compression.Radiology 1986; 158:355–360.

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Linam and Munden—Sonography in Children With Suspected Acute Appendicitis

Figure 5. Transverse color Doppler image of the right lower quadrant.

This dilated appendix has increased flow to the wall.

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