Seasonal variation in emergency general surgery

Objective: The aim of this study was to assess the seasonal variation in emergency general surgery (EGS) admissions. Background: Seasonal variation in medical conditions is well established; however, its impact on EGS cases remains unclear. Methods: The National Inpatient Sample (NIS) database was queried over an 8-year period (2004-2011) for all patients with diagnosis of acute appendicitis, acute cholecystitis, and diverticulitis. Elective admissions were excluded. The following data for each admission were recorded: age, sex, race, admission month, major operative procedure, hospital region, and mortality. Seasons were defined as follows: Spring (March, April, May), Summer (June, July, August), Fall (September, October, November), and Winter (December, January, February). X11 procedure and spectral analysis were performed to confirm seasonal variation. Results: A total of 63,911,033 admission records were evaluated of which 493,569 were appendicitis, 395,838 were cholecystitis, and 412,163 were diverticulitis. Seasonal variation is confirmed in EGS (F=159.12, P<0.0001) admissions. In the subanalysis, seasonal variation was found in acute appendicitis (F=119.62, P<0.0001), acute cholecystitis (F=37.13, P<0.0001), and diverticulitis (F=69.90, P<0.0001). The average monthly EGS admission in Winter was 11,322±674. The average monthly EGS admission in Summer was higher than that of Winter by 13.6% (n=1542;95% CI: 1180-1904, P<0.001). Conclusions: Hospitalization due to EGS adheres to a consistent cyclical pattern, with more admissions occurring during the Summer months. Although the reasons for this variability are unknown, this information may be useful for hospital resource reallocation and staffing.