Negative Appendectomy and Imaging Accuracy in the Washington State Surgical Care and Outcomes Assessment Program

Objective: To evaluate negative appendectomy (NA) and the relationship of NA and computed tomography (CT) and/or ultrasound (US). Summary Background Information: NA may be influenced by the use and accuracy of preoperative CT/US. The Surgical Care and Outcomes Assessment Program (SCOAP) gathers chart-abstracted process of care data (such as CT/US accuracy) for general surgical procedures (including appendectomy) at most Washington State hospitals. Methods: We determined the prevalence of NA and CT/US concordance at the 15 SCOAP hospitals with >50 consecutive patients undergoing appendectomy (2006-2007). Results: The number of patients who underwent urgent appendectomies was 3540. The percentage of patients who had imaging (CT-91%) was 86% (women-89%, men-83%). The use of imaging ranged across hospitals from 56% to 97%. There was 91% agreement between imaging and pathology report findings (92.3%-CT and 82.4%-US). The overall rate of NA was 6% (women-8%, men-4%). The prevalence of NA was 9.8% among patients having no imaging, 8.1% among those having an US, and 4.5% in those having a CT. Among patients with NA, CT/US was obtained in 75%; correct in 10% and incorrect or ambiguous in 65%. Higher rates of NA were correlated with lower rates of CT/US concordance (r = -0.57). There was no significant difference in rates of perforation between those with (17%) and without (15%) imaging (P = 0.2). There were significant increases in the use of CT/US and decreases in NA over the time period (P < 0.01). Conclusions: The prevalence of NA at SCOAP hospitals decreased significantly. Variation in NA between hospitals was linked closely to CT/US accuracy suggesting CT/US accuracy should be considered a measure of quality in the care of patients with presumed appendicitis.