Diffusion-weighted imaging of the renal and adrenal lesions.

Objectives: The purpose of this study was to calculate the apparent diffusion coefficient (ADC) values of different renal and adrenal lesions to evaluate the ability of diffusion-weighted imaging in characterizing masses and determining malignancy. Methods: A total of 52 patients consisting of 67 renal lesions and 28 patients with 33 adrenal lesions in addition to 50 healthy controls with normal kidneys were enrolled in the study. Diffusion-weighted imaging was performed with b factors of 0, 500, and 1000 s/mm(2), and the ADCs of the normal kidney and renal and adrenal lesions were calculated. Results: The mean (SD) ADCs of the renal cortex and medulla of the control group were 2.08 (0.22) x 10(-3) and 1.94 (0.18) x 10(-3) mm(2)/s, respectively. Focal renal lesions were as follows: simple cysts (2.94 [0.20] x 10(-3) mm(2)/s), hemorrhagic cysts (1.71 [0.38] x 10(-3) mm(2)/s), angiomyolipomas (1.40 [0.21] x 10(-3) mm(2)/s), renal cell carcinomas (1.06 [0.39] x 10(-3) mm(2)/s), metastases (1.50 [0.13] x 10(-3) mm(2)/s), and hydronephrosis (1.54 [0.25] x 10(-3) mm(2)/s). The mean ADCs of all these pathologies were significantly different when compared with normal parenchyma. Diffusion-weighted imaging was also able to differentiate angiomyolipomas and hemorrhagic cysts from renal cell carcinomas. Adrenal lesions were subgrouped as adenomas (1.41 [0.27] x M10(-3) mm(2)/s), nonadenomatous solid masses (1.08 [0.28] x 10(-3) mm(2)/s), and cysts (2.82 [0.24] x 10(-3) mm(2)/s). The mean ADCs of adenomas were significantly different when compared with nonadenomatous solid masses and cysts. Conclusions: Our findings show that ADC measurement has a potential ability to differentiate benign and malignant focal renal and adrenal lesions with the guidance of conventional sequences. When used alone, diffusion-weighted imaging may lead to misdiagnoses due to overlapping ADCs of the lesions.