Abstract
IntroductionIgA nephropathy (IgAN) is the commonest global cause of glomerulonephritis. Extent of fibrosis, tubular atrophy and glomerulosclerosis predict renal function decline. Extent of renal fibrosis is assessed with renal biopsy which is invasive and prone to sampling error. We assessed the utility of non-contrast native T1 mapping of the kidney in patients with IgAN for assessment of renal fibrosis.MethodsRenal native T1 mapping was undertaken in 20 patients with IgAN and 10 healthy subjects. Ten IgAN patients had a second scan to assess test-retest reproducibility of the technique. Native T1 times were compared to markers of disease severity including degree of fibrosis, eGFR, rate of eGFR decline and proteinuria.ResultsAll patients tolerated the MRI scan and analysable quality T1 maps were acquired in at least one kidney in all subjects. Cortical T1 times were significantly longer in patients with IgAN than healthy subjects (1540 ms ± 110 ms versus 1446 ± 88 ms, p = 0.038). There was excellent test-retest reproducibility of the technique, with Coefficient-of-variability of axial and coronal T1 mapping analysis being 2.9 and 3.7% respectively. T1 correlated with eGFR and proteinuria (r = − 0.444, p = 0.016; r = 0.533, p = 0.003 respectively).Patients with an eGFR decline > 2 ml/min/year had increased T1 times compared to those with a decline < 2 ml/min/year (1615 ± 135 ms versus 1516 ± 87 ms, p = 0.068), and T1 time was also higher in patients with a histological ‘T’-score of > 0, compared to those with a ‘T’-score of 0 (1575 ± 106 ms versus 1496 ± 105 ms, p = 0.131), though not to significance.ConclusionsCortical native T1 time is significantly increased in patients with IgAN compared to healthy subjects and correlates with markers of renal disease. Reproducibility of renal T1 mapping is excellent. This study highlights the potential utility of native T1 mapping in IgAN and other progressive nephropathies, and larger prospective studies are warranted.
Highlights
IgA nephropathy (IgAN) is the commonest global cause of glomerulonephritis
Cortical native T1 time is significantly increased in patients with IgAN compared to healthy subjects and correlates with markers of renal disease
This study highlights the potential utility of native T1 mapping in IgAN and other progressive nephropathies, and larger prospective studies are warranted
Summary
IgA nephropathy (IgAN) is the commonest global cause of glomerulonephritis. Extent of fibrosis, tubular atrophy and glomerulosclerosis predict renal function decline. Extent of renal fibrosis is assessed with renal biopsy which is invasive and prone to sampling error. We assessed the utility of non-contrast native T1 mapping of the kidney in patients with IgAN for assessment of renal fibrosis. While some patients have indolent, Graham-Brown et al BMC Nephrology (2019) 20:256 most reproducible predictors of progressive renal function decline in IgAN [3,4,5]. Renal biopsy is essential for a diagnosis of IgAN. There have been only a few sequential renal biopsy studies to assess response to treatment in IgAN [10] (NCT02112838), a concern voiced by some investigators is the potential for sampling error, where biopsy samples are not necessarily representative of the whole kidney, adversely influencing any evaluation of treatment response [11]. Non-invasive screening tests that could assess the extent of interstitial fibrosis, or active inflammation are highly desirable
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