Pseudotumours in chronic kidney disease: Can diffusion-weighted MRI rule out malignancy

• Conventional non-contrast MRI is unable to distinguish CKD pseudotumors from RCCs.
• Pseudotumours in a background of CKD do not show restricted diffusion.
• CKD pseudotumours demonstrate high ADC values whereas RCCs show restricted diffusion.
• DW-MRI is reliable in ruling out malignancy incase of pseudotumours found in chronic kidney disease.
• DW-MRI may obviate contrast administration and/or tissue sampling in renal pseudotumours and prevent inadvertent surgeries.

ObjectivesTo evaluate whether diffusion-weighted MRI (DW-MRI) can distinguish pseudotumours in chronic kidney disease (CKD pseudotumours) from renal-cell-carcinomas (RCCs) (with or without CKD) and whether it offers additional benefit over conventional MRI.MethodsOne-hundred patients underwent MDCT, MRI and DW-MRI (at b-values of 0 and 500 s/mm2) for evaluation of focal renal lesions. Of these, 20 patients with 40 CKD pseudotumours and 36 patients with 40 RCCs were retrospectively analyzed. T1-weighted, T2-weighted, diffusion-weighted images were evaluated, apparent-diffusion-coefficient (ADC) values were compared and receiver-operating-characteristic (ROC) curves were drawn to establish cut-off ADC-values.Results92.5% of CKD pseudotumours remained indeterminate after conventional MRI. On DW-MRI, none of them showed restricted diffusion and thus malignancy could be ruled out in 100% of the lesions. In contrast, all the solid RCCs showed diffusion restriction. Mean ADC-value for CKD pseudotumours was significantly higher than RCCs and surrounding diseased parenchyma [2.50 vs 1.56 (×10−3 mm2/s) (P < 0.0001) and 2.05 (×10−3 mm2/s) (P = 0.0001) respectively]. ROC analysis for differentiating CKD pseudotumours and RCC yielded high sensitivity (91.7%) and specificity (100%) for cut-off ADC-value of 2.04 (×10−3 mm2/s).ConclusionsCKD pseudotumors usually remain indeterminate on conventional non-contrast MRI. DW-MRI can distinguish CKD pseudotumors from RCCs and offers a non-contrast non-invasive alternative for ruling out malignancy.