US07 - Renal Mass Imaging Modality, Does BMI Matter?

Introduction/Purpose: Renal cell carcinoma (RCC) is a subtype of kidney cancer that has a well-associated pattern on imaging that is often reported as being suspicious for malignancy. When a renal mass is suspicious of malignancy, the mass size on imaging is important for clinical decision-making, due to the fact that malignant potential increases with size. The preoperative analysis of size is crucial for the suspicion of malignancy as there is a known positive correlation between increasing size and increased histological grade. With other considerations, the National Comprehensive Cancer Network recommendations for ablation, partial, or radical nephrectomy are based on 3, 4, and 7 centimeters by greatest dimension, respectively. With the high cost of imaging and the significant impact on operative planning, it is of urgent importance to better understand the quality of these imaging modalities and expose any trends associated with patient characteristics that may exist, particularly when the size of renal masses carries significant weight in the choice of surgical procedure. The guidance on optimal preoperative imaging is lacking, especially with respect to body mass index (BMI). We aim to discern which modalities accurately predict the renal mass size and if increased BMI decreases consistency between imaging modalities.

Methods or Case Description: A retrospective multi-institutional chart review was performed for adult patients undergoing nephrectomy or elective ureteroscopy with lithotripsy between January 2018 and December 2021. This included 221 total charts, from three different hospitals and six operating surgeons. Where the patients’ data were collected from the electronic medical records. Patients

were excluded if the renal mass pathology was angiomyolipoma, no data was

obtained, lack of specimen report, or, lack radiology reports. Differences between the greatest dimensions and volume of masses were compared between each imaging modality, computerized tomography (CT), ultrasound (US), and magnetic resonance imaging (MRI). Predictive accuracy analysis was performed using t-tests for parametric and Wilcoxon signed-rank tests for non-parametric data while BMI effect on imaging accuracy demanded ANOVA for parametric and Kruskal–Wallis for non-parametric data.



Outcomes: Among 221 patients, age, gender, and the number of radical or partial nephrectomies were compared (Table 1). The difference when comparing the greatest dimension of computerized tomography (CT) with contrast to the pathology reported greatest dimension was found to be statistically significant (p=0.03) in combined BMI groups (Table 2). Whereas CT without contrast has a greater difference compared to the pathology report (p=0.018). There was also a difference when comparing the volume of CT without contrast to the pathology report (p=0.046). But there was shown to be no statistically significant difference with MRI, US, and CT Urogram when compared with the greatest dimension in specimen reports. There were also no statistically significant differences in the mean volume of CT with contrast, MRI, US, or CT Urogram when compared to the volume from the specimen reports.




Table 1. Patient Demographics

Table 2. Greatest Mean Difference Between Imaging Modalities with Respect to BMI


Conclusion: From the data given it was shown that CT without contrast is not reliable for preoperative renal mass sizing if utilizing the greatest dimension. It was also determined that the size of the renal mass on imaging, when compared to the pathology, has an accurate relationship for ultrasound BMI < 35 kg/m2, CT with contrast, and MRI.