Kidney iron deposition by R2* is associated with haemolysis and urinary iron

Abstract

Kidney iron deposition measured by R2* (magnetic resonance imaging) MRI is posited to result from tubular reabsorption of filtered haemoglobin due to intravascular haemolysis. In chronically transfused sickle cell disease (SCD), R2* is elevated and positively correlated with lactate dehydrogenase (LDH). To account for contributions to renal iron from systemic iron overload, we evaluated kidney R2*, urinary iron and haemolysis markers in 62 non-transfused SCD patients. On multivariate analysis, kidney R2* was associated with urinary iron and LDH (R² = 0·55, P < 0·0001). Our study confirms that kidney R2* is associated with intravascular haemolysis and raises important questions regarding the role of iron in SCD nephropathy.

Figure 1.

Univariate analyses of kidney R2* vs. (A) urinary iron, (B) LDH, (C) cell-free plasma hemoglobin, and (D) hemoglobin on log-transformed x- and y-axes. Blue line is log-log fit and red line indicates upper limit of normal kidney R2* of 34 Hz.