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Updated: May 2, 2026
In Vivo, Percutaneous, Needle Based, Optical Coherence Tomography of Renal Masses
Published on: March 30, 2015
MR imaging in the characterization of small renal masses
Jonathon M Willatt1, Hero K Hussain, Suzanne Chong
1Department of Radiology, University of Michigan, Ann Arbor, MI, USA, jwillatt@med.umich.edu.
Objective:
The aim of our study was to evaluate the effectiveness of MR imaging for the characterization of small (<2 cm) renal lesions described as indeterminate on prior US or CT.
Materials And Methods:
Sixty-three small renal masses in 51 patients considered indeterminate on prior ultrasound or CT scans were included in the study. A retrospective evaluation of the examinations was performed independently by two body magnetic resonance imaging (MRI) radiologists who were unaware of the final diagnosis. A 3-point confidence scale (1: benign, 2: indeterminate, and 3: malignant) was established to determine the level of suspicion for malignancy. Interobserver agreement was determined with a weighted kappa statistic. The diagnosis was verified by imaging follow-up of at least 24 months (mean 60 months) in 53 lesions and by pathology in 10 lesions.
Results:
MRI detected all eight malignancies in the series. There were eight malignant lesions and two benign lesions among those with pathologic follow-up. No interval growth or evidence of malignancy in the remaining 53 lesions was found for a minimum of 24 months by repeat imaging. The sensitivity, specificity, positive predictive value, and negative predictive value of MRI for differentiating benign from malignant small renal lesions were 100% (62.9-100%, 95% CI), 94.5% (84.9-98.8%, 95% CI), 72.7% (39.1-93.6%, 95% CI), and 100% (93.1-100%, 95% CI), respectively. The kappa value for interobserver agreement was 0.77 (95% CI 0.59-0.96, p-value <0.001).
Conclusion:
MR imaging is an effective method for characterizing small (<2 cm) renal masses found to be indeterminate by US or CT.
Insights
Magnetic resonance imaging (MRI) effectively characterizes small renal masses (<2 cm) that appear indeterminate on ultrasound (US) or computed tomography (CT). This imaging modality demonstrates high sensitivity and specificity in differentiating benign from malignant lesions.
Area of Science:
- Radiology
- Medical Imaging
- Oncology
Background:
- Small renal masses (<2 cm) often present as indeterminate findings on ultrasound (US) or computed tomography (CT).
- Accurate characterization of these lesions is crucial for appropriate patient management and avoiding unnecessary interventions.
Purpose of the Study:
- To evaluate the diagnostic effectiveness of magnetic resonance (MR) imaging for characterizing small renal lesions (<2 cm) initially deemed indeterminate by US or CT.
- To assess the accuracy of MR imaging in differentiating benign from malignant small renal masses.
Main Methods:
- Retrospective analysis of 63 small renal masses in 51 patients, previously classified as indeterminate.
- Independent review by two body MRI radiologists using a 3-point confidence scale for malignancy suspicion.
- Diagnosis verification through imaging follow-up (≥24 months) or pathological examination.
Main Results:
- MR imaging detected all eight malignancies present in the study cohort.
- High diagnostic performance: sensitivity 100%, specificity 94.5%, positive predictive value 72.7%, and negative predictive value 100%.
- Excellent interobserver agreement (kappa = 0.77) was observed among radiologists.
Conclusions:
- MR imaging is a highly effective tool for characterizing small renal masses (<2 cm) that are indeterminate on US or CT.
- MRI provides accurate differentiation between benign and malignant small renal lesions, aiding clinical decision-making.
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