I ran a google search on Appendicitis CT Scan Normal and found:
Missed Appendicitis AHRQ PSNET Patient Safety Network Cases & Commentaries WebMM Logo Published June 2003:
Although sensitivity of up to 100% has been reported for CT scans of the appendix (6), in typical practice the sensitivity is more likely to be 80%-96%.(8,9) Thus, clinicians should be aware of the possibility of false negative scans. Conversely, the specificity of appendiceal CT is not perfect. A Bayesian approach is needed: widespread use of CT in low-risk patients will lead to significant numbers of false positive test results and unnecessary appendectomies. In some cases, a period of inpatient or outpatient observation is warranted despite the CT report. Patient teaching (including thorough discharge instructions) and good communication are the routes to minimizing error.
The best approach to evaluating an ED patient with abdominal pain is to maintain suspicion for early disease, even disease not yet diagnosable, and instruct the patient accordingly. A nonspecific diagnosis of ”abdominal pain” can be appropriately followed by a discussion with the patient surrounding ”red flag” signs and symptoms as well as the expected course. If abdominal tenderness is absent and there is no justification for CT scan or extended hospital observation, careful instructions must include warning signs of more serious disease. Then, if the patient returns with appendicitis, the initial encounter cannot be counted as a failure, but as a success.
8. Ege G, Akman H, Sahin A, Bugra D, Kuzucu K. Diagnostic value of unenhanced helical CT in adult patients with suspected acute appendicitis. Br J Radiology. 2002;75:721-5.[ go to PubMed]
9. Maluccio MA, Covey AM, Weyant MHJ, Eachempati SR, Hydo LJ, Barie PS. A prospective evaluation of the use of emergency department computed tomography for suspected acute appendicitis. Surg Infect. 2001;2:205-11.[ go to PubMed ]