Renal mass imaging modalities: does body mass index (BMI) matter?

Area of Science:

• Urology
• Radiology
• Oncology

Background:

• Accurate renal mass size measurement is critical for kidney cancer management.
• Current imaging guidelines lack specificity regarding body mass index (BMI) influence.
• Understanding imaging modality variability is essential for patient care.

Purpose of the Study:

• To evaluate the accuracy of different imaging modalities in measuring renal mass size.
• To determine if patient BMI affects the accuracy of renal mass size measurements.
• To inform optimal imaging strategies for renal masses.

Main Methods:

• Multi-institutional chart review of 236 adult patients undergoing nephrectomy (2018-2021).
• Patients categorized into four BMI groups (18.5-24.9, 25-29.9, 30-34.9, ≥35).
• Comparison of mass greatest length measurements from pathology reports with CT, MRI, and renal ultrasound.

Main Results:

• Contrast-enhanced CT and MRI showed significant differences compared to pathological measurements.
• Obese patients (BMI 3 and 4) had significantly different size estimates on contrast-enhanced CT compared to normal weight patients (BMI 2).
• No significant BMI-related differences in size estimates were observed for renal ultrasound or non-contrast CT.

Conclusions:

• Contrast-enhanced CT is less accurate for estimating renal mass size in patients with BMI > 30.
• Caution is advised when using contrast-enhanced CT for mass size estimation in obese individuals.
• While vital for tissue enhancement, CT's accuracy for size measurement diminishes with increasing BMI.