title: Defining the current negative appendectomy rate: for whom is preoperative computed tomography making an impact?
abstract: BACKGROUND
  Historically, the negative appendectomy rate (NAR) for patients operated on for acute appendicitis (AA) has exceeded 20%. We sought to define the current NAR with increased use of computed tomography (CT) and laparoscopy.
  
  
  METHODS
  Records of 1425 consecutive patients undergoing appendectomy for suspicion of AA during the past 7 years at a single institution were reviewed. The NAR was calculated and compared with earlier data from this institution (1995-1999). Statistical methods included the Fisher exact test and the Student t test; differences of P < .05 were considered statistically significant.
  
  
  RESULTS
  The overall NAR was 7.65% compared to 16.3% over the period 1995-1999 (P = .0001), without a change in the perforation rate. Concurrently, the rate of preoperative CT increased from 32% to 95%. CT was associated with a lesser NAR only among adult females (7.6% vs 20.8%, P = .005) but not among adult males or children. No difference in NAR was noted in comparing laparoscopic and open appendectomy. Patients without AA had a greater mean duration of symptoms and lower white blood cell count at presentation than those with AA. Most patients undergoing negative appendectomy had a CT, and more than 50% had CT interpretations that were positive for, or could not exclude, AA.
  
  
  CONCLUSIONS
  The NAR in our hospital has decreased progressively to approximately 5%. Although preoperative CT is used in almost all patients, it is only associated with a lesser NAR among adult females. False-positive CTs may contribute to the residual NAR, and further data are needed to determine whether subgroups of male or pediatric patients benefit from preoperative CT.
authors.affiliation: Department of Surgery, New York-Presbyterian Hospital and Weill Medical College of Cornell University, New York, NY 10065, USA. plw9001@nyp.org
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Wagner
authors.forename: Soumitra R
authors.initials: SR
authors.lastname: Eachempati
authors.forename: Kevin
authors.initials: K
authors.lastname: Soe
authors.forename: Frederic M
authors.initials: FM
authors.lastname: Pieracci
authors.forename: Jian
authors.initials: J
authors.lastname: Shou
authors.forename: Philip S
authors.initials: PS
authors.lastname: Barie
mesh_terms: D000328:Adult; D001062:Appendectomy; D001064:Appendicitis / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D010535:Laparoscopy; D008297:Male; D014057:Tomography, X-Ray Computed