title: Nontraumatic acute abdominal pain: unenhanced helical CT compared with three-view acute abdominal series.
abstract: OBJECTIVE
  To prospectively evaluate and compare the diagnostic accuracy of unenhanced helical computed tomography (CT) for patients with nontraumatic acute abdominal pain with that of traditional abdominal radiography.
  
  
  METHODS
  Institutional review board approval and informed consent were obtained; this study was completed before implementation of the HIPAA. Ninety-one patients (44 men; 47 women; age range, 18-84 years; mean age, 48.5 years) with acute nontraumatic abdominal pain over a 7-month period were referred by the emergency department of one institution. These patients underwent a three-view acute abdominal series (AAS) and unenhanced helical CT. AAS included an upright chest radiograph and upright and supine abdominal radiographs. Unenhanced helical CT images with 5-mm collimation were obtained from the lung bases to the pubic symphysis, without intravenous, oral, or rectal contrast material. AAS and unenhanced helical CT images were each separately and prospectively interpreted by a different experienced radiologist who was blinded to patient history and the images and interpretation of the other examination for each patient. Final diagnosis was established with surgical, pathologic, and clinical follow-up. The sensitivity, specificity, accuracy, positive predictive value, negative predictive value, and positive and negative likelihood ratios were calculated for AAS and unenhanced helical CT. Confidence intervals of 95% were calculated for each value with the standard equation for population proportions. Results of AAS and unenhanced helical CT examinations were compared with chi2 analysis.
  
  
  RESULTS
  Among the 91 patients examined, unenhanced helical CT yielded an overall sensitivity, specificity, and accuracy of 96.0%, 95.1%, and 95.6%, respectively. The AAS interpretations yielded an overall sensitivity, specificity, and accuracy of 30.0%, 87.8%, and 56.0%, respectively. The accuracy of unenhanced helical CT was significantly greater than the accuracy of AAS (P < .05).
  
  
  CONCLUSIONS
  AAS is an insensitive technique in the evaluation of nontraumatic acute abdominal pain in adults. Unenhanced helical CT is an accurate technique in the evaluation of adult patients with nontraumatic acute abdominal pain and should be considered as an alternative to radiography as the initial imaging modality.
authors.affiliation: Department of Radiology, Wilford Hall Medical Center, Lackland Air Force Base, Tex, USA. amackersie@hotmail.com
authors.forename: Andrew B
authors.initials: AB
authors.lastname: MacKersie
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lane
authors.forename: Robert T
authors.initials: RT
authors.lastname: Gerhardt
authors.forename: Harry A
authors.initials: HA
authors.lastname: Claypool
authors.forename: Sean
authors.initials: S
authors.lastname: Keenan
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Katz
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Tucker
mesh_terms: D000006:Abdomen, Acute / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D036542:Tomography, Spiral Computed / Q000379:methods