title: Bosniak classification system: inter-observer and intra-observer agreement among experienced uroradiologists.
abstract: BACKGROUND
  The Bosniak classification is a diagnostic tool for the differentiation of cystic changes in the kidney. The process of categorizing renal cysts may be challenging, involving a series of decisions that may affect the final diagnosis and clinical outcome such as surgical management.
  
  
  OBJECTIVE
  To investigate the inter- and intra-observer agreement among experienced uroradiologists when categorizing complex renal cysts according to the Bosniak classification.
  
  
  METHODS
  The original categories of 100 cystic renal masses were chosen as "Gold Standard" (GS), established in consensus by two experienced uroradiologists. Three experienced uroradiological readers were blinded from the previous CT reports. Weighted κ was calculated to assess agreement, defined as: fair, 0.21-0.40; moderate, 0.41-0.60; good, 0.61-0.80; and very good, 0.81-1.00.
  
  
  RESULTS
  For readers the distribution of correctly classified lesions were as follows: BI, 95-100%; BII, 59-93%; BIIF, 54-92%; BIII, 58-95%; and B IV, 77-100% for the first review. Weighted κ for inter-observer/intra-observer variation was for Reader A: 0.85/0.99, Reader B: 0.97/0.99, and Reader C: 0.98/0.99, (P ≤ 0.001).
  
  
  CONCLUSIONS
  According to the calculated weighted κ all readers performed "very good" for both inter-observer and intra-observer variation. Most variation was seen in cysts catagorized as Bosniak II, IIF, and III. These results show that radiologists who evaluate complex renal cysts routinely may apply the Bosniak classification reproducibly.
authors.affiliation: Urological Research Center, Department of Urology, Fredericia Hospital, Fredericia, and Institute of Regional Health Services Research, University of Southern Denmark, Denmark olegraumann@dadlnet.dk.
authors.forename: Ole
authors.initials: O
authors.lastname: Graumann
authors.affiliation: Urological Research Center, Department of Urology, Fredericia Hospital, Fredericia, and Institute of Regional Health Services Research, University of Southern Denmark, Denmark.
authors.forename: Susanne S
authors.initials: SS
authors.lastname: Osther
authors.affiliation: Department of Radiology, Odense University Hospital, Odense, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Karstoft
authors.affiliation: Department of Radiology, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Arne
authors.initials: A
authors.lastname: Hørlyck
authors.affiliation: Urological Research Center, Department of Urology, Fredericia Hospital, Fredericia, and Institute of Regional Health Services Research, University of Southern Denmark, Denmark.
authors.forename: Palle J S
authors.initials: PJ
authors.lastname: Osther
mesh_terms: D000368:Aged; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging; D052177:Kidney Diseases, Cystic / Q000000981:diagnostic imaging*; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011856:Radiographic Image Enhancement; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards; D014283:Triiodobenzoic Acids
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; C044834:iodixanol
keywords: CT; Kidney neoplasms; inter-observer variation; intra-observer variation; renal cystic masses