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Imaging Appendicitis in Children 

Imaging Appendicitis in Children
Chapter:
Imaging Appendicitis in Children
Author(s):

Christoph I. Lee

DOI:
10.1093/med/9780190223700.003.0025
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The addition of CTRC [CT with rectal contrast] after a negative ultrasonography result increased the imaging sensitivity [for appendicitis] from 44% to 94%.

Garcia Peña et al.1

Research Question:

What is the accuracy of ultrasound and limited CT with rectal contrast in diagnostic pediatric appendicitis?

Funding:

None reported.

Year Study Began:

1998

Year Study Published:

1999

Study Location:

Single large urban pediatric teaching hospital.

Who Was Studied:

Children and adolescents aged 3–21 years with equivocal findings for acute appendicitis.

Who Was Excluded:

Pregnant patients, patients with previous appendectomy, or contraindication to rectal contrast.

How Many Patients:

139

Study Overview:

Prospective cohort study. All children with suspected appendicitis were evaluated by a senior surgical resident under the supervision of an attending pediatric surgeon. Patients with equivocal findings were initially evaluated with pelvic ultrasound. If the ultrasound was definitive, laparotomy was performed. If the ultrasound was negative or inconclusive (e.g., appendix not visualized), then limited CT with rectal contrast of the pelvis was performed.

Exposure:

Pelvic ultrasounds were performed by a pediatric radiology fellow or attending using a 5.0 and/or 7.5 MHz linear array transducer. CT with rectal contrast was performed with helical technique, limited scanning, and after rectal contrast was placed via a rectal cathether. No oral or intravenous contrast was used. Diagnosis of appendicitis was based on detecting a fluid-filed, distended tubular structure measuring at least 6 mm in diameter and/or periappendiceal inflammatory changes.

Follow-Up:

All children who did not undergo surgery were contacted for follow-up at 2 weeks by telephone. Medical records of all patients were reviewed 4–6 months after study completion.

Endpoints:

Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of ultrasound-CT with rectal contrast. Surgeons also estimated likelihood of appendicitis on a 1–10 scale and case management plans before imaging, after ultrasound, and after CT.

Results

  • Among 177 children evaluated for appendicitis during the 6-month study period, 2.3% (4/177) of patients were discharged without imaging, 19.2% (34/177) went directly to surgery without imaging, and 78.5% (139/177) underwent diagnostic imaging for clinically equivocal findings (this latter group comprised the study cohort) (Table 25.1).

  • Ultrasound identified a normal appendix in 2.4% (2/83) of patients without appendicitis, while limited CT with rectal contrast identified a normal appendix in 84% (62/74) of patients without appendicitis.

  • Positive findings on ultrasound or CT influenced surgeons’ estimated likelihood of appendicitis (P = 0.001 and P < 0.001, respectively).

  • Negative ultrasound findings did not change the surgeons’ clinical confidence in ruling out appendicitis (P = 0.06), but negative CT findings did increase the surgeons’ confidence level (P < 0.001).

  • Ultrasound correctly changed management plans in 18.7% (26/139) of patients, while limited CT with rectal contrast correctly changed management plans in 73.1% (79/108) of patients.

Table 25.1. The Trial’s Key Findings

Imaging for Appendicitis

Sensitivity

Specificity

PPV

NPV

Accuracy

Ultrasound

44%

93%

79%

75%

76%

CT after negative or equivocal ultrasound

97%

94%

85%

99%

94%

Ultrasound-CT study protocol

94%

94%

90%

97%

94%

PPV = positive predictive value; NPV = negative predictive value.

Criticisms and Limitations:

This study was performed at a single academic institution; thus, its findings may not be widely generalizable. The true performance characteristics for limited CT with rectal contrast cannot be determined from this study, as CT was performed only following a negative or indeterminate ultrasound. Radiologists performing ultrasounds were aware of the surgeon’s estimated likelihood of appendicitis, potentially biasing their interpretations of ultrasound examinations. Radiologists interpreting CT scans may have been the same persons who performed the ultrasounds, thus potentially biasing the interpretation of the CT scans.

Other Relevant Studies and Information:

  • Ultrasound may diagnose appendicitis in a substantial proportion of pediatric patients with equivocal clinical findings without the need for radiation. For the pediatric patient population with a low pretest probability of appendicitis, ultrasound remains the primary diagnostic modality.

  • For children with equivocal clinical findings, the American College of Radiology recommends beginning with ultrasound (appropriateness rating of 8 out of 9).2 A normal appendix must be seen to reliably exclude appendicitis in patients with persistent symptoms. If the appendix is not visualized or the ultrasound is nondiagnostic, CT scan with contrast should be considered (appropriateness rating of 7 out of 9).2

  • If CT is performed in children with equivocal findings, most experts now recommend contrast-enhanced CT rather than CT without contrast, and intravenous contrast is preferred over oral or rectal contrast.2,3,4

  • Some institutions are able to offer MRI as a primary diagnostic tool for appendicitis in children with relatively high sensitivity and specificity using an abbreviated scanning protocol with the need for contrast or sedation.5

Summary and Implications:

CT with contrast after a negative or indeterminate pelvic ultrasound leads to very high accuracy in diagnosing acute appendicitis in children (Figure 25.1).

Figure 25.1 Contrast-enhanced axial CT image of the pelvis status post rectal contrast administration with acute appendicitis (arrow).

Figure 25.1 Contrast-enhanced axial CT image of the pelvis status post rectal contrast administration with acute appendicitis (arrow).

Clinical Case: Appendicitis in Children

Case History:

A 3-year-old male presents to the pediatric emergency department with abdominal pain and nausea. The patient has an elevated white blood cell count and the parents report that their son has not had an appetite all day. You order an ultrasound of the right lower quadrant, and the pediatric radiologists reports that the appendix was not visualized and there was no evidence of abscess or fluid collections in the right lower quadrant. What should you do next?

Suggested Answer:

Based on this study, contrast-enhanced CT should be considered in cases with equivocal ultrasound findings. This patient has signs and symptoms suspicious of appendicitis. Since the appendix was not visualized, you should order a CT with intravenous contrast. The use of additional oral or rectal contrast is institution dependent, and, in many cases, intravenous contrast alone should be sufficient for obtaining a very high accuracy for diagnosing pediatric acute appendicitis.

References

1. Garcia Peña BM, Mandl KD, Kraus SJ, et al. Ultrasonography and limited computed tomography in the diagnosis and management of appendicitis in children. JAMA. 1999;282:1041–1046.Find this resource:

2. Rosen MP, Ding A, Blake MA, et al. ACR Appropriateness Criteria right lower quadrant pain—suspected appendicitis. J Am Coll Radiol. 2011;8(11):749–755.Find this resource:

3. Anderson SW, Soto JA, Lucey BC, et al. Abdominal 64-MDCT for suspected appendicitis: the use of oral and IV contrast material versus IV contrast material only. AJR Am J Roentgenol. 2009;193(5):1282–1288.Find this resource:

4. Kepner AM, Bacasnot JV, Stalman BA. Intravenous contrast alone vs intravenous and oral contrast computed tomography for the diagnosis of appendicitis in adult ED patients. Am J Emerg Med. 2012;30(9):1765–1773.Find this resource:

5. Kulaylat AN, Moore MM, Engbrecht BW, et al. An implemented MRI program to eliminate radiation from the evaluation of pediatric appendicitis. J Pediatr Surg. 2015;50(8):1359–1363.Find this resource: