What causes diminished corticomedullary differentiation in renal insufficiency?
PURPOSE: To investigate whether the loss of corticomedullary differentiation (CMD) on T1-weighted MR images due to renal insufficiency can be attributed to changes in T1 values of the cortex, medulla, or both. MATERIALS AND METHODS: Study subjects included 10 patients (serum creatinine range 0.6-3.0 mg/dL) referred for suspected renovascular disease who underwent 99mTc-diethylene triamine pentaacetic acid (DTPA) renography to determine single kidney glomerular filtration rate (SKGFR) and same-day MRI, which included T1 measurements and unenhanced T1-weighted gradient echo imaging. Corticomedullary differentiation on T1-weighted images was assessed qualitatively and quantitatively. RESULTS: SKGFR values ranged from 3.5 to 89.4 mL/minute based on radionuclide studies. T1 relaxation times of the medulla exceeded those of renal cortex by 147.9+/-176.0 msec (mean+/-standard deviation [SD]). Regression analysis showed a negative correlation between cortex T1 and SKGFR (r=-0.5; P=0.03), where
