title: CT of renal cell carcinoma: assessment of collecting system invasion.
abstract: OBJECTIVE
  Although renal collecting system invasion is not considered in the current TNM staging system, this finding may be relevant in terms of treatment planning and prognosis. The objective of this study was to investigate the frequency of collecting system invasion in renal cell carcinoma (RCC) and to assess the diagnostic performance of excretory phase CT for the assessment of collecting system invasion.
  
  
  METHODS
  We conducted a retrospective study of 261 patients (171 men and 90 women; average age, 61 years; age range, 32-86 years) who underwent CT before nephrectomy for RCC between November 2008 and July 2011 at a single institution. On excretory phase contrast-enhanced CT images, two radiologists independently determined whether RCC components caused a filling defect within the collecting system and whether the RCC was in contact to the collecting system wall or separated from it. Histopathology served as the standard of reference. Interreader agreement and diagnostic performance tests for the detection of collecting system invasion were calculated.
  
  
  RESULTS
  Histopathology identified collecting system invasion exclusively in clear cell RCC that showed a filling defect within the collecting system on excretory phase CT images (5.4%, 14/261). Tumors separated from or in contact with the collecting system on imaging (both readers; 94.6%, 247/261) did not show collecting system invasion on histopathology (sensitivity, 100%; specificity, 100%). Interreader agreement was excellent (κ, 0.965; 95% CI, 0.93-0.99).
  
  
  CONCLUSIONS
  CT provides reliable assessment of collecting system invasion in patients with RCC, with excellent sensitivity and specificity.
authors.affiliation: 1 Department of Radiology, Memorial Sloan-Kettering Cancer Center, Radiology Academic Offices, Rm C278, 1275 York Ave, New York, NY 10065.
authors.forename: Christoph A
authors.initials: CA
authors.lastname: Karlo
authors.forename: Pier L
authors.initials: PL
authors.lastname: Di Paolo
authors.forename: Hedvig
authors.initials: H
authors.lastname: Hricak
authors.forename: Satish K
authors.initials: SK
authors.lastname: Tickoo
authors.forename: Paul
authors.initials: P
authors.lastname: Russo
authors.forename: Oguz
authors.initials: O
authors.lastname: Akin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D003287:Contrast Media; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000000981:diagnostic imaging* / Q000473:pathology; D009367:Neoplasm Staging; D009392:Nephrectomy; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media