title: Variability in computed tomography diameter measurements of solid renal masses.
abstract: OBJECTIVE
  To determine whether the frequency of intra-observer measurement discrepancies ≥5 mm for solid renal masses varies by renal mass characteristics and CT contrast phase.
  
  
  METHODS
  This HIPAA-compliant retrospective study was approved by our IRB. We selected single CT images performed during the nephrographic phase (NP) of renal enhancement in 97 patients, each with a single solid renal mass. Mass location, margin, heterogeneity, and growth pattern were assessed. Six readers measured each mass on two occasions >3 weeks apart. Readers also measured the masses on images in 50 patients who had corticomedullary phase (CMP) images obtained during the same study. Results were assessed using Chi-square/Fisher's exact and Wilcoxon Signed Rank tests, and logistic regression analyses.
  
  
  RESULTS
  For NP to NP comparisons, intra-reader measurement differences ≥5 mm were seen for 3.7% (17/463) of masses <4 cm, but increased to 16.8% (20/119) for masses >4 cm (p < 0.0001). Masses with poorly defined margins (15.9% [22/138] vs. 3.4% [15/444] for well-defined margins, p < 0.0001) and heterogeneity (15.3% [22/144], vs. 5.0% [14/282] for minimally heterogeneous, vs. 0.6% [1/156] for homogeneous, p < 0.0001), were more frequently associated with measurement differences ≥5 mm. Differences ≥5 mm were more frequent when only CMP images were utilized (14% [42/299]), or when CMP images were compared with NP images (26% [77/299]).
  
  
  CONCLUSIONS
  A ≥5 mm intra-reader variation in measured size of solid renal masses <4 cm is uncommon for NP to NP comparisons. Variation increases when masses are ≥4 cm, poorly defined, or heterogeneous; or when CMP images are utilized.
authors.affiliation: Department of Radiology, University of Michigan Hospitals, 1500 East Medical Center Drive, Room B1D502G, Ann Arbor, MI, 48109-5030, USA.
authors.forename: Lorenzo P
authors.initials: LP
authors.lastname: Orton
authors.forename: Richard H
authors.initials: RH
authors.lastname: Cohan
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Davenport
authors.forename: Robert A
authors.initials: RA
authors.lastname: Parker
authors.forename: Aishwarya
authors.initials: A
authors.lastname: Parameswaran
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Caoili
authors.forename: Ravi K
authors.initials: RK
authors.lastname: Kaza
authors.forename: Isaac R
authors.initials: IR
authors.lastname: Francis
authors.forename: James H
authors.initials: JH
authors.lastname: Ellis
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Wolf
authors.forename: Khaled
authors.initials: K
authors.lastname: Hafez
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging / Q000473:pathology; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D036542:Tomography, Spiral Computed / Q000379:methods*; D047368:Tumor Burden
chemical_list: D003287:Contrast Media