Non-invasive investigation of kidney disease in type 1 diabetes by magnetic resonance imaging

Abstract

Aims/hypothesis Pathophysiological abnormalities in early diabetic nephropathy are poorly understood. We employed MRI to characterise renal perfusion, tissue oxygenation and kidney size in non-diabetic volunteers and type 1 diabetic patients without and with early renal disease. Methods We studied ten control participants (C; age 40.0 [range 31-54] years), nine longstanding normotensive type 1 diabetic patients (T1Normo; age 40.1 [31-50] years, estimated glomerular filtration rate [eGFR] 83.4± 10.6 ml min -1 1.73 m -2) and eight microalbuminuric type 1 diabetic patients (T1Micro; age 42.4 [33-52] years, eGFR 71.6±13.7 ml min -1 1.73 m -2). Six microalbuminuric patients were restudied after 4 weeks without renin- angiotensin-aldosterone system inhibitors. Phase contrast angiography and kidney blood oxygen level dependent (BOLD) (R 2*) MRI were performed, before and during water diuresis. Contrast-enhanced MRI was performed at baseline urine flow rate. Renal artery flow, renal vascular resistance (RVR), cortical and medullary volumes, and R2*were determined. Results Renal cortical and medullary volumes were similar in all groups (cortex: C 108±16, T1Normo 112±21, T1Micro 111±10 cm 3/1.73 m 2; medulla: C 35±14, T1Normo 29±10, 33±6 cm 3 /1.73 m 2). RVR increased from control to normoalbuminuric to microalbuminuric type 1 diabetic patients (C 0.061±0.018, T1Normo 0.077± 0.014, T1Micro 0.093±0.024 mmHg ml-1 min -1 1.73 m -2, ANOVA p=0.012). RVR correlated inversely with eGFR in normoalbuminuric, but not in microalbuminuric diabetic patients. Renal artery flow was lower in the whole diabetes cohort (control 740±205 vs diabetes 591±128 ml min -1 1.73 m -2, p=0.035). Conclusions/interpretation Cortical and medullary volumes remain normal in early diabetic nephropathy. Decreased renal flow in longstanding normoalbuminuric type 1 diabetic patients may reflect intrarenal vascular stiffening, whereas in the microalbuminuric patients it may also reflect increased intraglomerular pressure. © Springer-Verlag 2011.