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Kidney Week

Abstract: TH-PO435

Comparison of the Total Kidney Volumes Using the Ellipsoid Equation and Manual Segmentation in ADPKD

Session Information

Category: Genetic Diseases of the Kidneys

  • 1201 Genetic Diseases of the Kidneys: Cystic

Authors

  • Jang, Hyun Bae, McGill University, Montreal, Quebec, Canada
  • Reinhold, Caroline, McGill University Health Centre, Montreal, Quebec, Canada
  • Alam, Ahsan, McGill University Health Centre, Montreal, Quebec, Canada
Background

Total kidney volume (TKV) is an important prognostic biomarker of disease progression in autosomal dominant polycystic kidney disease (ADPKD). The gold standard of manual segmentation TKV (mTKV) is time and labour-intensive. The ellipsoid equation TKV (eTKV) is commonly used in clinical practice, but assumes uniform growth of the kidneys. Our study examined the correlation between the eTKV and mTKV and we examined cases individually where there was misclassification.

Methods

We analyzed coronal T2-weighted MRI slices for 143 patients with ADPKD from a single centre. eTKV was determined using standard orthogonal measurements. The ground truth mTKV was performed by a single trained individual. Pearson’s correlation coefficient was calculated and a Bland-Altman analysis was performed. A confusion matrix was generated to illustrate the misclassification in the Mayo Imaging Classification (MIC) between the two approaches. We explored cyst imaging features where the difference in TKV methods was ≥20%.

Results

The mean age of the cohort was 45 (SD 15), 46% were male, hypertension prevalence was 71%, the median eGFR was 76 ml/min/1.73m2 (IQR 46-107), height-adjusted TKV was 865 mL/m (IQR 490-1307), and tolvaptan use was 45%. The correlation coefficient between both TKV measures was 0.96. The Bland-Altman analysis showed wide limits of agreement [-40.43%, 25.15%], and 24 patients were reclassified by one MIC risk category. Of the 25 patients (17%) who exhibited ≥20% difference between the two measures, 23 patients were characterized as having large exophytic cysts.

Conclusion

The eTKV is efficient and generally reliable for calculating TKV, but it may lose accuracy in patients with large exophytic cysts. Further study should explore the association of exophytic cysts with kidney disease progression. Understanding whether exophytic cysts should be included in the TKV estimation may aid in risk stratification.

Confusion Matrix of Mayo Imaging Class Determined By Total Kidney Volume Using Ellipsoid Equation (eTKV) and Manual Segmentation (mTKV)
  eTKV
  1A1B1C1D1E2
mTKV1A1100000
1B3240000
1C0846200
1D0082310
1E0002130
2000002