title: Why can we not see a normal appendix on CT? An evaluation of the factors influencing nonvisualization of a normal appendix by 64-slice MDCT.
abstract: OBJECTIVE
  The aim of this study was to identify the factors that prevent the visualization of a normal appendix by 64-slice MDCT.
  
  
  METHODS
  Thirty-nine consecutive patients with a normal appendix not visualized during routine abdominal CT and without a history of abdominal surgery were selected for this study. In addition, 100 consecutive patients with a clearly visualized normal appendix by CT were selected as controls. Two radiologists, by consensus, evaluated MDCT images for cecum level, pericecal fat content, presence of small bowel dilatation, presence of pericecal fluid, presence of cecal wall thickening, and identification of the ileocecal valve.
  
  
  RESULTS
  Patients with a nonvisualized normal appendix had a significantly lower cecum level, minimal pericecal fat, and a higher amount of pericecal fluid and were less likely to have an identified ileocecal valve (46.2%, 79.5%, 17.9%, and 76.9%, respectively) than patients with a clearly visualized appendix (18%, 9%, 4%, and 100%, respectively) (all P<.01). The presence of small bowel dilatation and cecal wall thickening was not statistically significant (7.7% vs. 8% and 7.7% vs. 9%, respectively) (all P>.01).
  
  
  CONCLUSIONS
  The factors that influence the nonvisualization of a normal appendix on MDCT images are as follows: a low cecum level, minimal pericecal fat, presence of pericecal fluid, and nonidentification of the ileocecal valve.
authors.affiliation: Department of Radiology, East-West Neo Medical Center, Kyung-Hee University, Gangdong-Gu, Seoul, Republic of Korea. khcppp@lycos.co.kr
authors.forename: Hyun Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Dal Mo
authors.initials: DM
authors.lastname: Yang
authors.forename: Hyun Phil
authors.initials: HP
authors.lastname: Shin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001065:Appendix / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000706:statistics & numerical data*; D055815:Young Adult