Diffusion-weighted MRI in inflammatory renal lesions: all that glitters is not RCC!

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Distinguishing inflammatory renal lesions from renal-cell carcinomas (RCCs) is crucial for appropriate patient management.
• Diffusion-weighted magnetic resonance imaging (DW-MRI) offers insights into tissue microstructure.

Purpose of the Study:

• To evaluate diffusion characteristics of inflammatory renal lesions.
• To assess the utility of apparent diffusion coefficient (ADC) values in differentiating these lesions from RCCs.

Main Methods:

• Eighty-eight patients with focal renal lesions underwent multidetector computed tomography (MDCT), MRI, and DW-MRI.
• Retrospective analysis of 20 inflammatory lesions and 36 RCCs was performed.
• Receiver operating characteristic (ROC) curves were generated to determine cut-off ADC values.

Main Results:

• Both inflammatory lesions and RCCs demonstrated restricted diffusion.
• Abscesses showed markedly restricted diffusion in fluid areas, while RCCs exhibited free diffusion in cystic portions.
• ADC values for both abscesses (1.12 × 10⁻³ mm²/s) and RCCs (1.56 × 10⁻³ mm²/s) were significantly lower than normal renal parenchyma (2.34 × 10⁻³ mm²/s) and differed significantly between lesion types (P < 0.0001).

Conclusions:

• Restricted diffusion is observed in both abscesses and RCCs, with greater extent in inflammatory lesions.
• ADC values provide a valuable tool for characterizing indeterminate renal lesions.
• A cut-off ADC value of 1.41 × 10⁻³ mm²/s demonstrated high sensitivity (100%) and specificity (78.1%) in differentiating inflammatory lesions from RCCs.