title: Volumetric analysis of colonic distention according to patient position at CT colonography: diagnostic value of the right lateral decubitus series.
abstract: OBJECTIVE
  The purpose of this study was to compare total colonic gas volume and segmental luminal distention according to patient position on CT colonography (CTC), as well as to determine which two views should constitute the routine protocol.
  
  
  METHODS
  Volumetric analysis was retrospectively performed on CTC examinations from 146 adults (mean age, 59.2 years; 81 men and 65 women; mean body mass index [BMI], 30.9) for whom supine, prone, and right lateral decubitus series were sequentially obtained using continuous low-pressure CO2 insufflation. Total colonic gas volumes were assessed using a novel automated volumetric tool. In addition, two radiologists scored distention by segment using a 4-point scale (4=optimal; 3=adequate; 2=inadequate; 1=collapsed).
  
  
  RESULTS
  Mean (±SD) colonic gas volumes for supine, prone, and decubitus positioning were 1617±567, 1441±505, and 1901±627, respectively (p<0.001). Colonic volume was highest on the right lateral decubitus series in 73.3% (107/146) and lowest in 6.2% (9/146) of cases, whereas the prone series was highest in 0.7% (1/146) and lowest in 73.3% (107/146) of cases. Overall mean segmental reader scores and percentages of inadequate or collapsed for supine, prone, and decubitus positions were 3.48, 3.33, and 3.71 and 10.4%, 12.1%, and 4.2%, respectively (p<0.001). The only mean segmental scores below 3.0 were the sigmoid colon on supine (2.68) and prone (2.58) series, compared with 3.23 on decubitus series (p<0.001). Improvement in distention in both decubitus and supine positions over the prone position increased further with increasing BMI (p<0.001).
  
  
  CONCLUSIONS
  The right lateral decubitus position consistently yields the best colonic distention at CTC and significantly improves evaluation of the sigmoid colon. Prone distention was the worst, particularly as BMI increased. Routine supine and decubitus positioning should be considered for standard CTC protocols, particularly in obese individuals. Automated volumetric analysis provides for rapid objective assessment of colonic distention.
authors.affiliation: 1 Department of Radiology, University of Wisconsin School of Medicine & Public Health, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Pickhardt
authors.forename: Joshua
authors.initials: J
authors.lastname: Bakke
authors.forename: Jarret
authors.initials: J
authors.lastname: Kuo
authors.forename: Jessica B
authors.initials: JB
authors.lastname: Robbins
authors.forename: Meghan G
authors.initials: MG
authors.lastname: Lubner
authors.forename: Alejandro Muñoz
authors.initials: AM
authors.lastname: del Rio
authors.forename: David H
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D002245:Carbon Dioxide / Q000008:administration & dosage; D003106:Colon / Q000000981:diagnostic imaging* / Q000187:drug effects; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003287:Contrast Media / Q000008:administration & dosage; D004106:Dilatation / Q000379:methods; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning / Q000379:methods*; D011029:Pneumoradiography / Q000379:methods*; D016684:Prone Position; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D003287:Contrast Media; D002245:Carbon Dioxide
keywords: CT colonography (CTC); colorectal cancer; distention; quality assurance; screening