On the Role of Ultrasonography and CT Scan in the Diagnosis of Acute Appendicitis

Abstract

The purposes of this study were to revisit the utility of ultrasonography (USG) as a primary imaging modality in acute appendicitis (AA) and to establish the role of CT scan as a second-line/problem-solving modality. All cases of suspected AA were referred for urgent USG. USG was done with standard protocol for appendicitis. Limited computed tomographic (CT) scan [NCCT ± CECT (IV contrast only)] was done for the lower abdomen and pelvis where sonographic findings were equivocal. One hundred and twenty-one patients were referred for USG for suspected appendicitis. Eight-four patients underwent surgery for AA based on clinical as well as imaging findings, of whom 76 had appendicitis confirmed at histopathology. Three patients were misdiagnosed (3.6 %) on USG as appendicitis. Of 76 patients of appendicitis confirmed histopathologically, 63 (82.8 %) had features of appendicitis on USG and did not require any additional imaging modality. Of 121 patients, 12 (10 %) needed CT scan because of atypical features on USG. Of these 12 patients, seven had retrocecal appendicitis, and three high-up paracolic appendicitis. USG alone had sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 81, 88, 92.6, 71.6, and 83 %, respectively. When combined with CT scan in select cases, the sensitivity, specificity, PPV, NPV, and accuracy of combined USG + CT scan were 96 % (P = 0.0014), 89 %, 93 %, 93.5 % (P = 0.0001), and 93 % (P = 0.0484), respectively. Twenty-eight (23 %) patients were given alternative diagnosis on USG. Dedicated appendiceal USG should be used as a primary imaging modality in diagnosing or excluding AA. Appendiceal CT can serve as a problem-solving modality.

Keywords: Appendicitis; CT scan; Ultrasonography.

Fig. 1

Thirty-one-year-old man. Longitudinal section of an inflamed appendix demonstrating classic features. Note the enlarged appendix (diameter, 9.2 mm) with periappendiceal inflammatory changes

Fig. 2

Unruptured tubal ectopic pregnancy in a 19-year-old woman was mistaken sonologically as acute appendicitis

Fig. 3

A 53-year-old woman complained of persistent pain in RIF. USG was equivocal. CT scan was done as a problem-solving tool. Contrast-enhanced CT [axial (a) and coronal (b) plane images] clearly depicts changes of acute appendicitis. Note the relatively high-placed, paracolic position of the appendix. CT scan findings were confirmed at surgery