Magnetic resonance detection of kidney iron deposition in sickle cell disease: a marker of chronic hemolysis.

PURPOSE

To study the pattern, etiology, and significance of renal iron accumulation in chronically transfused sickle cell disease (SCD) and thalassemia major (TM) patients using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Magnetic resonance imaging (MRI) was performed in 75 SCD patients, 73 TM patients, and 16 healthy controls. Multiecho gradient echo protocols were used to measure T2* reciprocals (R2*) in the kidney, liver, and heart. Kidney R2* was compared to tissue iron estimates, serum iron markers, and surrogates of intravascular hemolysis by univariate regression.

RESULTS

Mean R2* in SCD patients was 55.3+/-45.3 Hz, compared with 22.1+/-11 Hz in TM patients and 21.3+/-5.8 Hz in control subjects (P<0.001). Kidney R2* decreased with advancing age (R2=0.09, P<0.02). Kidney R2* correlated strongly with increased serum lactate dehydrogenase levels found in SCD (R2=0.55, P<0.001), but was independent of hepatic iron concentration and cardiac R2*. Kidney R2* did not correlate with blood pressure, creatinine, cardiac index, or right and left ejection fraction.

CONCLUSION

Intravascular hemolysis, not chronic transfusion, causes renal hemosiderosis in SCD. Prospective trials are necessary to determine whether kidney R2* is a biomarker for hemolysis-mediated vascular complications in SCD.