Epidemiology of Incidental Renal Lesions: Insights from 117,826 Whole-Body MRI Examinations

Steven M Monda¹, Sabrina H Rossi², Madhurima Datta³, Viviane Dang¹, Srinivasan Nallandhighal¹, Tristan Barrett², Udit Singhal¹, Zixiong Huang¹, Hiroshi Kikuchi¹, Kristian Stensland¹, Todd Morgan¹, Alex Exuzides³, Grant D Stewart², Simpa Salami¹ 

¹University of Michigan, Ann Arbor, MI, ²University of Cambridge, London, United Kingdom, ³Prenuvo, Vancouver, BC, Canada 

INTRODUCTION AND OBJECTIVES: 

Most renal cell carcinomas (RCC) are incidentally detected on cross-sectional imaging obtained for unrelated indications. To assess prevalence and predictors of incidental renal lesions of concerning size (≥4cm and ≥7cm), we evaluated a large cohort of individuals undergoing whole body MRI. 

METHODS: 

We analyzed individuals imaged at Prenuvo, a company offering screening non-contrast 1.5T whole body MRI, from January 2020 - June 2025. All reported renal lesions of known size were assessed; individuals with prior RCC were excluded. Associations between ≥4 cm lesions, that were not simple cysts, with RCC risk factors (age, sex, obesity, hypertension, family history of kidney cancer, alcohol, smoking, diet) were examined using univariable and multivariable logistic regression with adjustment for false discovery (8 comparisons). Secondary analyses examined associations with lesions ≥7 cm and angiomyolipoma (AML). 

RESULTS: 

Among 117,826 individuals receiving whole body MRI (mean age 48.1, 46% female), 26.7% (31,460) had simple cysts. Complex cysts and solid lesions were identified in 3,664 individuals (3.1%). Of these, 52.0% (n= 1,905) were <1 cm and 92.8% (n= 3,338) were <3 cm. 4.2% (n= 155) and 1.1% (n= 41) of identified renal lesions were ≥4 cm and ≥7 cm, respectively. 

On univariable analyses, male sex (odds ratio (OR) 2.0), increasing age (per 10 years: OR 1.7), hypertension (OR 2.3), smoking (>20 pack-year: OR 3.8), BMI (per 5kg/m^2: OR 1.3) and family history of kidney cancer (OR 2.1) were associated with a renal lesion ≥ 4 cm (p<0.05), with similar associations for lesions ≥7 cm (age, sex, and family history: p<0.05). After multivariable analysis and BH adjustment, age and family history retained significance (BH adjusted p value<0.05). Female sex (OR 4.6) and age (OR 1.4) were associated with AML (p<0.001). 

CONCLUSIONS: 

Most MRI-detected renal lesions were small and likely clinically insignificant, with the vast majority measuring <3 cm (92.8%). Risk factors for larger, more concerning lesions (≥4 cm and ≥7 cm) mirrored those for RCC. These findings highlight the challenge of early detection of clinically relevant tumors that warrant further evaluation, while discriminating from the indolent majority.

SOURCE OF FUNDING: SMM is supported by grant T32 CA180984 from the NIH/NCI Advanced Training in Urologic Oncology and the Clark Family Fellowship in Kidney Cancer Research 

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