title: Targeted delayed scanning at CT urography: a worthwhile use of radiation?
abstract: OBJECTIVE
  To determine whether ureteral segments not filled with contrast material at computed tomographic (CT) urography ever contain tumor detectable only by filling these segments with contrast material.
  
  
  METHODS
  In this institutional review board-approved, HIPAA-compliant retrospective study, with waiver of informed consent, databases were searched for all patients who underwent heminephroureterectomy or ureteroscopy between January 1, 2001, and December 31, 2009, with available CT urography findings in the 12 months prior to surgery or biopsy and patients who had undergone at least two CT urography procedures with a minimum 5-year follow-up between studies. One of two radiologists blinded to results of pathologic examination recorded location of unfilled segments, time of scan, subsequent filling, and pathologic or 5-year follow-up CT urography results. Tumors were considered missed in an unfilled segment if tumor was found at pathologic examination or follow-up CT urography in the same one-third of the ureter and there were no secondary signs of a mass with other index CT urography sequences. Estimated radiation dose for additional delayed sequences was calculated with a 32-cm phantom.
  
  
  RESULTS
  In 59 male and 33 female patients (mean age, 66 years) undergoing heminephroureterectomy, 27 tumors were present in 41 partially nonopacified ureters in 20 patients. Six tumors were present in nonopacified segments (one multifocal, none bilateral); all were identifiable by means of secondary signs present with earlier sequences. Among 182 lesions biopsied at ureteroscopy in 124 male and 53 female patients (mean age, 69 years), 28 tumors were present in nonopacified segments in 25 patients (four multifocal, none bilateral), all with secondary imaging signs detectable without delayed scanning. In 64 male and 29 female patients (mean age, 69 years) who underwent 5-year follow-up CT urography, three new tumors were revealed in three patients; none occurred in the unfilled ureter at index CT urography. Estimated radiation dose from additional sequences was 4.3 mSv per patient.
  
  
  CONCLUSIONS
  Targeted delayed scanning at CT urography yielded no additional ureteral tumors and resulted in additional radiation exposure.
authors.affiliation: Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, Room C76F, New York, NY 10065, USA.
authors.forename: Kalesha
authors.initials: K
authors.lastname: Hack
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Pinto
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Gollub
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007472:Iohexol; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014516:Ureteral Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D018666:Ureteroscopy; D014567:Urography / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol