title: Utility of repeated abdominal CT scans after prior negative CT scans in patients presenting to ER with nontraumatic abdominal pain.
abstract: OBJECTIVE
  The purpose of this study was to analyze diagnostic yield of repeat computed tomography (CT) after negative initial CT versus yield of initial CT in patients presenting repeatedly to emergency room (ER) for nontraumatic abdominal pain. Medical costs and radiation exposure from repeat CT could be reduced if repeat CT after negative initial CT has a low diagnostic yield.
  
  
  METHODS
  Patients included consecutive adults presenting to William Beaumont Hospital, from 2007 to 2010, undergoing abdominal CT for nontraumatic abdominal pain retrospectively identified by medical diagnostic and CT procedural codes. Exclusion criteria were prior abdominal trauma, recent abdominal surgery, and known chronic gastrointestinal disease. The CT was labeled "positive" if findings explained patient's abdominal pain or was clinically significant. Positivity rate was compared for repeat versus initial CT.
  
  
  RESULTS
  Among 200 consecutive patients undergoing (659) multiple CTs (mean age = 45.7 years, 74 % female), positivity rate for initial CT (22.5 %) was significantly higher than positivity rates for CT#2 (8.4 %, p = 0.002), for CT#3 (4.9 %, p = 0.005), and for CT ≥ #4 (5.9 %, p = 0.006). Generally, CT positivity rate declined with increasing number of prior negative CTs. CT positivity rate was significantly higher in 100 patients undergoing single CT versus 155 patients undergoing repeat CTs (46.5 vs. 6.5 %, p = 0.0001). Positive repeat CT findings included intestinal mural thickening/mass (7), colitis (5), appendicitis (4), and other (14). Among 15 analyzed clinical parameters, two significantly predicted repeat CT positivity, namely, leukocytosis (p = 0.03) and APACHE-II-score >5 (p = 0.01). Repeat CTs constituted 47 % of all CTs.
  
  
  CONCLUSIONS
  Repeat abdominal CT after initially negative CT(s) performed for nontraumatic abdominal pain has a low diagnostic yield. Leukocytosis and APACHE-II score might help predict CT scan positivity. Data suggest restricted abdominal CT utilization in ER patients with multiple prior negative CTs. Findings warrant confirmation in prospective studies.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, William Beaumont Hospital, Oakland University William Beaumont School of Medicine, 3535 West 13 Mile Rd, Royal Oak, MI 48073, USA.
authors.forename: Borko
authors.initials: B
authors.lastname: Nojkov
authors.forename: Michael C
authors.initials: MC
authors.lastname: Duffy
authors.forename: Mitchell S
authors.initials: MS
authors.lastname: Cappell
mesh_terms: D015746:Abdominal Pain / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D019564:Unnecessary Procedures / Q000706:statistics & numerical data*