The use of abdominal computed tomography scan decreases the frequency of misdiagnosis in cases of suspected appendicitis.

Background: Despite considerable experience the reported frequency of misdiagnosis in patients undergoing appendectomy continues in the range of 20% to 40% in some populations.

Methods: We developed a clinical guideline that recommended abdominal computed tomography (CT) for all nonpregnant adults in whom the diagnosis of appendicitis was suspected unless the diagnosis could be ruled out clinically. The records of adult patients that underwent appendectomy from July 1998 through October 2001 were reviewed. The clinical guideline was developed in July 2000.

Results: There were 194 appendectomies performed, 114 prior to the guideline and 80 after the development of the guideline. The rate of misdiagnosis decreased from 25% to 6% (P <0.05), the rate of CT use increased from 32% to 84% (P <0.05), and the perforation rate remained unchanged.

Conclusions: These results support the effectiveness of a clinical guideline that encourage the use of abdominal CT in decreasing the frequency of misdiagnosis in cases of suspected appendicitis.