MR Elastography for Noninvasive Assessment of Fibrosis in Diabetic Kidney Disease
There has been an increasing incidence of chronic kidney disease (CKD), particularly secondary to diabetes mellitus, in the USA leading to a large burden of cardiovascular mortality and renal failure. Kidney scarring, known as fibrosis, is considered the final common pathway of kidney injury leading to progressive impairment of renal function in diabetic nephropathy (DN). Therefore, it is important to know the degree of kidney fibrosis in order to determine treatment and prognosis, but there is currently no simple, reliable, and non-invasive way to do so. Kidney biopsy, the invasive gold standard, has sampling error and its risk precludes frequent repetition. A novel technique using magnetic resonance imaging known as MR elastography (MRE) has been developed to assess tissue elasticity. Our preliminary data suggests that tissue shear stiffness as measured using MRE may correlate with pathologic kidney fibrosis and/or kidney function in our pilot group of normal subjects and CKD patients. A finding that MRE could non-invasively estimate the degree of kidney fibrosis or scarring would greatly improve our care of patients with DN. It would provide a quantum leap in our ability to assess tissue damage, follow disease progression, and evaluate response to treatments designed to prevent fibrosis and slow tissue damage in patients with diabetic kidney disease. We are proposing to test whether non-invasively measured MRE elasticity, together with MR arterial spin labeling and phase contrast measurement of kidney perfusion, correlates with fibrosis as graded by kidney biopsy and with standard kidney function tests (creatinine based estimated glomerular filtration rate) in patients with Type 1 and Type 2 diabetes in early and late stages of DN. Furthermore, we will assess whether MRE measured shear stiffness is abnormal and can detect early kidney fibrosis in diabetic patients with hyperfiltration and/or microalbuminuria with preclinical DN prior to reductions in eGFR. This technique may allow differentiation of structural fibrotic changes from reversible functional changes in patients with hemodynamic effects that complicate evaluation of DN.

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