# Estimation of Kidney Volumes in Autosomal Dominant Polycystic Kidney Disease: A Comparison Between Manual Segmentation and Ellipsoid Formula

## TL;DR

This study compares two methods for estimating kidney volumes in a genetic kidney disease and finds the ellipsoid formula to be as accurate but faster than manual segmentation.

## Contribution

Demonstrates the ellipsoid formula as a reliable and faster alternative to manual segmentation for kidney volume estimation in ADPKD.

## Key findings

- Both methods showed excellent interobserver agreement with ICC ≥ 0.977.
- The ellipsoid formula was significantly faster for all radiologists without compromising accuracy.
- Bland–Altman analysis confirmed strong agreement between methods for the senior radiologist.

## Abstract

Objectives: Evaluate the agreement and interobserver variability between manual segmentation and the ellipsoid formula in estimating single kidney volume (SKV) in patients with autosomal dominant polycystic kidney disease (ADPKD). Methods: In this retrospective study, 130 unenhanced CT scans of ADPKD kidneys were analyzed. Three radiologists (one senior, two juniors) measured SKV using manual segmentation and the ellipsoid formula. Statistical analyses included intraclass correlation coefficient (ICC), Wilcoxon signed-rank test, Bland–Altman analysis, and paired t-tests to compare measurement values and computation times. Results: Both methods showed excellent interobserver agreement (ICC ≥ 0.977). No significant difference was observed in volume estimates between the two techniques (Wilcoxon p = 0.295). Bland–Altman analysis confirmed strong agreement between methods for the senior radiologist. The ellipsoid method was significantly faster for all readers (p < 0.05). Conclusions: The ellipsoid formula is a reliable, time-efficient alternative to manual segmentation for SKV estimation in ADPKD, offering comparable accuracy with reduced resource demands in clinical settings.