Renal cell carcinoma: attenuation values on unenhanced CT

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Renal cell carcinoma (RCC) is a common kidney malignancy.
• Accurate differentiation of RCC from benign renal lesions on unenhanced CT is crucial for patient management.
• Unenhanced CT attenuation values are a key imaging biomarker for characterizing renal masses.

Purpose of the Study:

• To analyze the attenuation values of pathologically proven renal cell carcinomas (RCCs) on unenhanced computed tomography (CT).
• To establish the range of attenuation values that suggest malignancy in renal lesions.
• To aid in the differentiation of malignant from benign renal masses based on CT imaging characteristics.

Main Methods:

• Retrospective review of 193 pathologically proven RCCs (≥1 cm) from 189 patients.
• Attenuation values were measured using region of interest (ROI) sampling (25-100 mm²) on unenhanced CT, excluding calcifications.
• Tumors were classified as homogeneous or heterogeneous based on visual inspection.

Main Results:

• All 193 RCCs exhibited noncalcified regions with attenuation values between 20-70 HU.
• 72.5% of RCCs fell entirely within this 20-70 HU range, termed the "danger zone."
• Minimum and maximum mean ROI attenuation values for RCCs were 27.5±10.4 HU and 39.7±10.6 HU, respectively.

Conclusions:

• Substantial noncalcified regions within the 20-70 HU range are characteristic of proven RCCs on unenhanced CT.
• Renal lesions with unenhanced CT attenuation values between 20-70 HU warrant further diagnostic workup.
• Lesions with attenuation values entirely outside the 20-70 HU range may be considered benign.