# Assessing asymmetrical kidney function in living donors: a retrospective cohort study on CT metrics

## TL;DR

This study evaluates how well CT scans can detect uneven kidney function in living donors, finding that current guidelines may not be reliable.

## Contribution

The study provides evidence on the limitations of CT-derived kidney metrics for detecting functional asymmetry in living donors.

## Key findings

- Kidney length discrepancy poorly indicates asymmetric kidney function (sensitivity: 28%).
- Cortical and total kidney volumes have high negative predictive values but low sensitivity.
- Current CT metrics show limited accuracy for identifying significant functional asymmetry.

## Abstract

Live donor kidney transplantation is the preferred kidney replacement therapy for eligible patients but requires thorough donor evaluation to minimise risks. Contemporary guidelines recommend split kidney function measurement in living donors only when there is a significant kidney size discrepancy, yet the evidence for this is poor, and practice varies nationally. This study evaluates the efficacy of CT-derived kidney metrics in detecting significant functional asymmetry.

We conducted a retrospective cohort analysis of 123 prospective living kidney donors at a regional transplant centre from June 2011 to October 2014, utilising CT to determine kidney and cortical volumes and lengths. Asymmetric kidney function (AKF), defined by > 10% function difference on DMSA scans, was correlated with CT measurements to calculate the diagnostic accuracy of current guidelines.

Among the prospective donors, the median age was 42 years, and 59.3% were female. The median split kidney function difference was 4%, with 25 individuals exhibiting > 10% AKF. Kidney length discrepancy proved to be a poor indicator of AKF (sensitivity: 28%, specificity: 84%). While negative predictive values for cortical and kidney volumes were high (96% and 93%, respectively), sensitivity was low, and specificity and positive predictive value did not meet satisfactory thresholds.

CT-derived metrics of kidney length, cortical, and total volume show limited sensitivity and specificity in identifying significant AKF. These findings provide evidence to support revised guideline development in the assessment of living kidney donors.

The online version contains supplementary material available at 10.1186/s12882-024-03634-7.