# Non-Invasive Magnetic resonance imaging Biomarkers to evaLuatE histology-proven kidney fibrosis in Chronic Kidney Disease (NIMBLE-CKD): an observational cohort study protocol

## TL;DR

This study aims to develop non-invasive MRI biomarkers to assess kidney fibrosis in chronic kidney disease, avoiding the need for invasive biopsies.

## Contribution

The study introduces postgadolinium contrast T1 mapping as a novel MRI technique for evaluating kidney fibrosis.

## Key findings

- A control group will establish baseline healthy kidney MRI parameters.
- MRI models will be derived and validated using biopsy-confirmed CKD patients.
- The study will assess the association between MRI markers and fibrosis severity.

## Abstract

Chronic kidney disease (CKD) affects 1 in 10 people worldwide and can progress towards kidney failure, which is best predicted by the severity of kidney fibrosis. Currently, kidney fibrosis can only be detected by invasive kidney biopsy which carries procedural risks with limitations on repeat testing. MRI techniques have emerged as potential surrogate markers for kidney fibrosis, though data remain limited. To date, no studies have examined postgadolinium contrast T1 mapping in kidney fibrosis despite its proven utility in assessing myocardial fibrosis. This study aims to develop a multiparametric MRI biomarker including postcontrast imaging to quantify kidney fibrosis in individuals with CKD.

In this observational cohort study, a control group of 20 healthy adult volunteers will establish healthy kidney MRI parameters. Two adult non-dialysis CKD cohorts (each n=24) who have undergone kidney biopsy within the last month will derive and validate the MRI models, respectively. Tubulointerstitial fibrosis on kidney biopsy will be assessed by Masson trichrome staining and quantified based on the percentage of cortex affected by blinded pathologists. All participants will undergo a single multiparametric kidney MRI including kidney volumetry, T1 mapping (pre-low-dose and post-low-dose contrast), T2 mapping, T2* mapping, diffusion weighted imaging and phase-contrast MRI of renal artery flow. The primary outcome will be the association between a composite multiparametric MRI marker and tubulointerstitial fibrosis with a minimum variance of 50%. The association between the multiparametric MRI marker and individual MRI variables, and tubulointerstitial fibrosis, estimated glomerular filtration rate and albuminuria will also be studied.

Ethics approval has been obtained by the Northern Sydney Local Health District Human Research Ethics Committee (2022/ETH00972). Results will be disseminated in relevant peer-reviewed journals and presented at academic conferences.

ACTRN12622000855729p (Pre-results).