Background: Appendectomy is the most common non-gynecologic surgery performed during pregnancy. There is little data investigating the accuracy of imaging studies in the diagnosis of appendicitis in pregnancy.
Objective: To evaluate the accuracy of clinical evaluation, as well as ultrasound (US) and computed tomography (CT) in accurately diagnosing appendicitis in pregnancy, as reflected in the negative appendectomy rate.
Methods: After receiving institutional approval, we retrospectively reviewed and analyzed the charts of 86 pregnant women who underwent an appendectomy at Brigham and Women’s Hospital between January 1, 1997 and January 1, 2006. The negative appendectomy rate was calculated in those patients that underwent clinical evaluation only (CLIN), those that had an US, and those that had an US followed by a CT scan (US-CT). Data were compared using Fisher’s exact test, taking p<0.05 as significant.
Results: There were 13 patients in the CLIN group with a negative appendectomy rate of 54% (7/13). Fifty-five patients underwent an US alone, with a negative appendectomy rate 36% (20/55). In the US-CT group, the negative appendectomy rate was 8% (1/13). There was a significant reduction in the negative appendectomy rate in US-CT group compared to CLIN (54% vs. 8%, p<0.05). This reduction was not achieved in the US group (p>0.05). In a small group of patients (n=5) only a CT scan was performed. The negative appendectomy rate was 60% as in 3 circumstances the clinicians ignored the CT findings and operated on the patient based on clinical exam. This further highlights the inaccuracy of clinical assessment in this patient population.
Conclusion: Our data documents a very high negative appendectomy rate in pregnant patient. Additional imaging can result in a significant reduction in this rate. Based on our data we recommend an US scan followed by a CT scan in patients with equivocal imaging, or clinical picture. Surgery based on clinical assessment should be avoided, to prevent a high rate of unnecessary procedures.

	Number of patients	Negative appendectomy rate (%)
CLIN	13	54% (7/13)
US	55	36% (20/55)
US-CT	13	8% (1/13)