Kelly Elizabeth Ainsworth MD, Presenter: Nothing to Disclose

Ehsan Haider MD, Abstract Co-Author: Nothing to Disclose

Pavel Zvonarev, Abstract Co-Author: Nothing to Disclose

Thomas Farrell, Abstract Co-Author: Nothing to Disclose

The literature has established that the diagnostic accuracy of unenhanced CT scans in diagnosing acute appendicitis are comparable to contrast enhanced CT and that unenhanced scans are useful for alternate diagnoses including diverticulitis, urinary tract disease, adnexal pathology, and small bowel disease. The caveat being that unenhanced CT has been useful for patients with a normal or obese body habitus and that slender patients with little periappendiceal fat makes the diagnosis of appendicitis difficult. The purpose of this study was to determine the relationship between abdominal girth and the ability to identify the normal appendix in male and female patients; and, if there is a cut-off girth above which IV and oral contrast is not necessary to identify the appendix.

Unenhanced helical CT scans of 108 patients (age range 4 – 83) who met the inclusion criteria were retrospectively evaluated to determine if a normal appendix could be identified by both a radiology resident and staff abdominal radiologist. A computer program was developed to estimate abdominal girth at the level of the iliac crests.

The appendix was seen in 74 and not seen in 34 patients, respectively. A one-way ANOVA determined abdominal girth was (on average) 19.42 cm larger for those patients whom the appendix was visible (p<0.001). ROC curve analyses demonstrate that for an abdominal girth greater than 105 cm (p<0.001), an unenhanced CT scan adequately identifies the appendix. Visibility by gender was not statistically significant (p=0.09). The inter-rater reliability coefficient was 0.75.

Unenhanced helical CT accurately detects the appendix in male and female patients with girth sizes exceeding 105 cm measured in the supine position at the level of the iliac crests. Ultrasound or contrast enhanced CT should remain the primary imaging choice for slender and pediatric patients.

Unenhanced helical CT decreases delays in diagnosis with oral contrast and the risks associated with IV contrast; detecting the appendix depends more on patient characteristics than on radiologist experience.

Ainsworth, K, Haider, E, Zvonarev, P, Farrell, T, Is There an Abdominal Girth Size above which Unenhanced CT Scanning Is Adequate in Diagnosing Acute Appendicitis?.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9001727.html