title: Estimation of total kidney volume in autosomal dominant polycystic kidney disease.
abstract: BACKGROUND
  In autosomal dominant polycystic kidney disease (ADPKD), obtaining measured total kidney volume (mTKV) by magnetic resonance (MR) imaging and manual tracing is time consuming. Two alternative MR imaging methods have recently been proposed to estimate TKV (eTKVellipsoid and eTKVPANK), which require less time.
  
  
  METHODS
  Cross-sectional and longitudinal diagnostic test study.
  
  
  METHODS
  Patients with ADPKD with a wide range of kidney function and an approved T2-weighted MR image obtained at the University Medical Centers of Groningen, Leiden, Nijmegen, and Rotterdam, the Netherlands, in 2007 to 2014. Test set for assessing reproducibility, n=10; cohort for cross-sectional analyses, n=220; and cohort for longitudinal analyses, n=48.
  
  
  METHODS
  Average times for eTKVellipsoid and eTKVPANK were 5 and 15 minutes, respectively. Bias is defined as (mTKV - eTKV)/mTKV × 100%; precision, as one standard deviation of bias.
  
  
  METHODS
  mTKV using manual tracing to calculate the area within kidney boundaries times slice thickness. Average time for mTKV was 55 minutes.
  
  
  RESULTS
  In the test set, intra- and intercoefficients of variation for mTKV, eTKVellipsoid, and eTKVPANK were 1.8% and 2.3%, 3.9% and 6.3%, and 3.0% and 3.4%, respectively. In cross-sectional analysis, baseline mTKV, eTKVellipsoid, and eTKVPANK were 1.96 (IQR, 1.28-2.82), 1.93 (IQR, 1.25-2.82), and 1.81 (IQR, 1.17-2.62) L, respectively. In cross-sectional analysis, bias was 0.02% ± 3.2%, 1.4% ± 9.2%, and 4.6% ± 7.6% for repeat mTKV, eTKVellipsoid, and eTKVPANK, respectively. In longitudinal analysis, no significant differences were observed between percentage change in mTKV (16.7% ± 17.1%) and percentage change in eTKVellipsoid (19.3% ± 16.1%) and eTKVPANK (17.8% ± 16.1%) over 3 years.
  
  
  CONCLUSIONS
  Results for follow-up data should be interpreted with caution because of the limited number of patients.
  
  
  CONCLUSIONS
  Both methods for eTKV perform relatively well compared to mTKV and can detect change in TKV over time. Because eTKVellipsoid requires less time than eTKVPANK, we suggest that this method may be preferable in clinical care.
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Edwin M
authors.initials: EM
authors.lastname: Spithoven
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Maatje D A
authors.initials: MD
authors.lastname: van Gastel
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: A Lianne
authors.initials: AL
authors.lastname: Messchendorp
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Niek F
authors.initials: NF
authors.lastname: Casteleijn
authors.affiliation: Department of Gastroenterology and Hepatology, Radboud University Medical Center, Nijmegen, the Netherlands.
authors.forename: Joost P H
authors.initials: JP
authors.lastname: Drenth
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Gaillard
authors.affiliation: Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Johan W
authors.initials: JW
authors.lastname: de Fijter
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Esther
authors.initials: E
authors.lastname: Meijer
authors.affiliation: Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Dorien J M
authors.initials: DJ
authors.lastname: Peters
authors.affiliation: Department of Radiology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Kappert
authors.affiliation: Neuroimaging Center, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Remco J
authors.initials: RJ
authors.lastname: Renken
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Folkert W
authors.initials: FW
authors.lastname: Visser
authors.affiliation: Department of Nephrology, Radboud University Medical Center, Nijmegen, the Netherlands.
authors.forename: Jack F M
authors.initials: JF
authors.lastname: Wetzels
authors.affiliation: Department of Nephrology, Erasmus Medical Center, Rotterdam, the Netherlands.
authors.forename: Robert
authors.initials: R
authors.lastname: Zietse
authors.affiliation: Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands. Electronic address: r.t.gansevoort@umcg.nl.
authors.forename: Ron T
authors.initials: RT
authors.lastname: Gansevoort
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000473:pathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D016891:Polycystic Kidney, Autosomal Dominant / Q000175:diagnosis*; D015203:Reproducibility of Results
keywords: Autosomal dominant polycystic kidney disease (ADPKD); PANK; ellipsoid; estimation methods; magnetic resonance imaging (MRI); total kidney volume (TKV); validation