title: Three-step sequential positioning algorithm during sonographic evaluation for appendicitis increases appendiceal visualization rate and reduces CT use.
abstract: OBJECTIVE
  The purpose of this article is to examine the rates of appendiceal visualization by sonography, imaging-based diagnoses of appendicitis, and CT use after appendiceal sonography, before and after the introduction of a sonographic algorithm involving sequential changes in patient positioning.
  
  
  METHODS
  We used a search engine to retrospectively identify patients who underwent graded-compression sonography for suspected appendicitis during 6-month periods before (period 1; 419 patients) and after (period 2; 486 patients) implementation of a new three-step positional sonographic algorithm. The new algorithm included initial conventional supine scanning and, as long as the appendix remained nonvisualized, left posterior oblique scanning and then "second-look" supine scanning. Abdominal CT within 7 days after sonography was recorded.
  
  
  RESULTS
  Between periods 1 and 2, appendiceal visualization on sonography increased from 31.0% to 52.5% (p < 0.001), postsonography CT use decreased from 31.3% to 17.7% (p < 0.001), and the proportion of imaging-based diagnoses of appendicitis made by sonography increased from 63.8% to 85.7% (p = 0.002). The incidence of appendicitis diagnosed by imaging (either sonography or CT) remained similar at 16.5% and 17.3%, respectively (p = 0.790). Sensitivity and overall accuracy were 57.8% (95% CI, 44.8-70.1%) and 93.0% (95% CI, 90.1-95.3%), respectively, in period 1 and 76.5% (95% CI, 65.8-85.2%) and 95.4% (95% CI, 93.1-97.1%), respectively, in period 2. Similar findings were observed for adults and children.
  
  
  CONCLUSIONS
  Implementation of an ultrasound algorithm with sequential positioning significantly improved the appendiceal visualization rate and the proportion of imaging-based diagnoses of appendicitis made by ultrasound, enabling a concomitant decrease in abdominal CT use in both children and adults.
authors.affiliation: 1 Department of Radiology, Stanford University School of Medicine, 300 Pasteur Dr, H1307, Stanford, CA 94305-5105.
authors.forename: Stephanie T
authors.initials: ST
authors.lastname: Chang
authors.forename: R Brooke
authors.initials: RB
authors.lastname: Jeffrey
authors.forename: Eric W
authors.initials: EW
authors.lastname: Olcott
mesh_terms: D000293:Adolescent; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001064:Appendicitis / Q000175:diagnosis*; D002648:Child; D002675:Child, Preschool; D044962:Data Compression / Q000379:methods / Q000592:standards; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007223:Infant; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D056888:Patient Positioning / Q000379:methods* / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D014463:Ultrasonography / Q000379:methods* / Q000706:statistics & numerical data*; D055815:Young Adult
keywords: appendicitis; diagnostic imaging; radiation protection; sonography; spiral CT