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Surgery. 2008 Aug;144(2):276-82. doi: 10.1016/j.surg.2008.03.040.

Defining the current negative appendectomy rate: for whom is preoperative computed tomography making an impact?

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Department of Surgery, New York-Presbyterian Hospital and Weill Medical College of Cornell University, New York, NY 10065, USA.



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.


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.


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.


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.

[Indexed for MEDLINE]

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