title: Urinary bladder pseudolesions on contrast-enhanced helical CT: frequency and clinical implications.
abstract: OBJECTIVE
  The goals of this study were to define the distinguishing characteristics and frequency of urinary bladder pseudolesions that are produced as opacified urine enters the bladder during contrast-enhanced helical CT of the abdomen and to evaluate the usefulness of delayed imaging in differentiating pseudolesions from true lesions.
  
  
  METHODS
  Contrast-enhanced routine CT scans of 184 patients were obtained prospectively. For each patient, we also obtained 5-min delayed images of the bladder. The images were evaluated for apparent focal thickening or polypoid lesions involving the bladder wall, findings that may represent bladder neoplasia, without knowledge of the indications for the scan, the patient's clinical history, or the patient's diagnosis. Apparent lesions that were visible on routine images and entirely absent on delayed images were considered to be pseudolesions.
  
  
  RESULTS
  Apparent lesions were identified on 20 (10.9%+/-4.5% [limits of the 95% confidence interval]) of the routine CT scans. Using delayed images, the 21 apparent lesions in these 20 patients were resolved as 13 pseudolesions and eight true lesions. Pseudolesions were present in 6.5%+/-3.6% of patients.
  
  
  CONCLUSIONS
  Pseudolesions of the bladder that are indistinguishable from true lesions pose a significant clinical problem in routine contrast-enhanced helical CT of the abdomen. Delayed imaging of the bladder is useful in distinguishing pseudolesions from true lesions.
authors.affiliation: Department of Radiology, Veterans Affairs Palo Alto Health Care System, CA 94304, USA.
authors.forename: E W
authors.initials: EW
authors.lastname: Olcott
authors.forename: M
authors.initials: M
authors.lastname: Nino-Murcia
authors.forename: J S
authors.initials: JS
authors.lastname: Rhee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011127:Polyps / Q000000981:diagnostic imaging; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging*; D001749:Urinary Bladder Neoplasms / Q000000981:diagnostic imaging*
chemical_list: D003287:Contrast Media