Prospective Double-Blinded Study of Abdominal-Pelvic Computed Tomography Guided by the Region of Tenderness: Estimation of Detection of Acute Pathology and Radiation Exposure Reduction
Presented as an abstract at the Society for Academic Emergency Medicine annual meeting, May 2009, New Orleans, LA.
Received 21 May 2009; received in revised form 15 October 2009; accepted 20 November 2009. published online 14 January 2010. Corrected Proof
Study objective
Computed tomography (CT) is increasingly used for emergency department (ED) patients with abdominal tenderness. CT-related radiation contributes to 2% of US cancers. We hypothesized that in the ED patient with nontraumatic abdominal tenderness, the tender region accurately delineates acute pathology. z axis–restricted CT guided by this region could detect pathology while reducing radiation dose.
Methods
This was a prospective double-blinded observational trial with informed consent and was institutional review board–approved and registered with ClinicalTrials.gov. A convenience sample of ED patients undergoing abdominal CT was recruited, excluding pregnant women, patients with altered mental status or abdominal sensation, preverbal children, and patients with abdominal trauma or surgery in the previous month. Before standard CT, physicians demarcated the tender region with labels invisible to radiologists on abdominal windows. Radiologists blinded to the tender region recorded cephalad-caudad limits of pathology on CT. Personnel blinded to pathology location recorded label positions on lung windows. Two hypothetical CT strategies were then explored: CT restricted to the tender region and CT from the cephalad skin marker to the lower caudad limit of the usual CT. The percentage of the pathologic region contained within the extent of the 2 hypothetical z axis restricted CTs was calculated. z axis reduction, which is linearly related to radiation reduction, from the restricted CTs was determined.
Results
One hundred two subjects were enrolled, 93 with complete data for analysis. Fifty-one subjects had acute pathology on CT. CT limited to the tender region would reduce z axis (radiation exposure) by 69% (95% confidence interval [CI] 60% to 78%). All acute pathology was included within these boundaries in 17 of the 51 abnormal cases (33%; 95% CI 22% to 47%). CT from the cephalad marker through the caudad abdomen and pelvis would reduce z axis (radiation exposure) by 38% (95% CI 29% to 48%). All acute pathology was included within these boundaries in 36 of 51 abnormal cases (71%; 95% CI 57% to 81%). With both strategies 1 and 2, the pathologic region was at least partially included within the CT region in the majority of cases (84% and 92%, respectively).
Conclusion
CT with z axis restriction based on abdominal tenderness could reduce radiation exposure but with a potentially unacceptably high rate of misdiagnosis, using our current methods. Further prospective study may be warranted to determine the diagnostic utility of partially visualized pathology.
⁎Department of Surgery, Division of Emergency Medicine, Durham, NC
†Department of Radiology, Duke University Medical Center, Durham, NC
Address for correspondence: Joshua S. Broder, MD, Box 3096, Duke University Medical Center, Durham, NC 27710; 919-684-5537, fax 919-681-8521
Supervising editor: Allan B. Wolfson, MD
Author contributions: JSB conceived the study and designed the trial. JSB and JLM supervised the conduct of the trial and data collection. JLM transcribed data forms and recorded sticker locations in a blinded fashion. CLH and EKP interpreted CT, blinded to clinical information and sticker locations. JSB managed and analyzed the data. JSB drafted the article, and all authors contributed substantially to its revision. CMM provided technical advice on radiation exposures and CT protocols. JSB takes responsibility for the paper as a whole.
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement. Beekley Corporation provided the skin surface adhesive markers used in this study free of charge.
ABSTRACT