Progress in the diagnosis of appendicitis: a report from Washington State's Surgical Care and Outcomes Assessment Program

Abstract

Background and objectives: Studies suggest that computed tomography and ultrasonography can effectively diagnose and rule out appendicitis, safely reducing negative appendectomies (NAs); however, some within the surgical community remain reluctant to add imaging to clinical evaluation of patients with suspected appendicitis. The Surgical Care and Outcomes Assessment Program (SCOAP) is a physician-led quality initiative that monitors performance by benchmarking processes of care and outcomes. Since 2006, accurate diagnosis of appendicitis has been a priority for SCOAP. The objective of this study was to evaluate the association between imaging and NA in the general community.

Methods: Data were collected prospectively for consecutive appendectomy patients (age > 15 years) at nearly 60 hospitals. SCOAP data are obtained directly from clinical records, including radiological, operative, and pathological reports. Multivariate logistic regression models were used to examine the association between imaging and NA. Tests for trends over time were also conducted.

Results: Among 19,327 patients (47.9% female) who underwent appendectomy, 5.4% had NA. Among patients who were imaged, frequency of NA was 4.5%, whereas among those who were not imaged, it was 15.4% (P < 0.001). This association was consistent for men (3% vs 10%, P < 0.001) and for women of reproductive age (6.9% vs 24.7%, P < 0.001). In a multivariate model adjusted for age, sex, and white blood cell count, odds of NA for patients not imaged were 3.7 times the odds for those who received imaging (95% CI: 3.0-4.4). Among SCOAP hospitals, use of imaging increased and NA decreased significantly over time; frequency of perforation was unchanged.

Conclusions: Patients who were not imaged during workup for suspected appendicitis had more than 3 times the odds of NA as those who were imaged. Routine imaging in the evaluation of patients suspected to have appendicitis can safely reduce unnecessary operations. Programs such as SCOAP improve care through peer-led, benchmarked practice change.

Figure One. Percent Negative Appendectomy by Imaging Modality, Stratified by Age Range

Asterisks indicate statistically significant comparison within each age category. No US results are reported for the elderly age group; only 29 elderly patients underwent preoperative US, which was felt too small of a number to make a comparison valid.

Figure Two. Appendectomy Patients Who Received Pre-operative Imaging

Hospitals are stratified by the year in which they joined SCOAP (represented by black lines that begin with the year in which that group of hospitals first submitted cases to SCOAP). The solid gray line indicates the number of patients who underwent pre-operative imaging as a percentage of all appendectomy patients from all hospitals participating in SCOAP in any particular year. Test for trend for the overall percentage of pre-operative imaging was significant (p < 0.001).

Figure Three. Appendectomy Patients with Negative Appendectomy

Hospitals are stratified by the year in which they joined SCOAP (represented by black lines that begin with the year in which that group of hospitals first submitted cases to SCOAP). The solid gray line indicates the number of negative appendectomies as a percentage of all appendectomy patients from all hospitals participating in SCOAP in any particular year. Test for trend for the overall percentage of negative appendectomies was significant (p < 0.001).

Figure Four. Appendicitis Patients with Perforation

Hospitals are stratified by the year in which they joined SCOAP (represented by black lines that begin with the year in which that group of hospitals first submitted cases to SCOAP). The solid gray line indicates the number of patients with perforation as a percentage of all patients with appendicitis from all hospitals participating in SCOAP in any particular year. There was no temporal trend for the overall frequency of perforation (p = 0.63).