In this study, the authors completed a theoretical model in which they analyzed the efficacy of renal ultrasound vs. CT imaging, but accounted for theoretical risk of secondary malignancy and its impact of life expectancy. As a theoretical model, it is not based on actual patient data, and therefore certain assumptions were made – different values may yield different results.
Their model inputs and sources from the literature as below:
In brief, upper tract urothelial carcinoma (UTUC) or renal cell carcinoma (RCC) are relatively rare sources of gross hematuria, and yet are the primary indication for upper tract evaluation in patients presenting with gross hematuria. On multivariable analysis, male gender and age over 50 years were significantly associated with a higher relative risk of upper tract malignancy (2.04 and 2.95, respectively). They utilized literature searches to identify the sensitivity of renal ultrasound (RUS) in identifying UTUC and RCC. They estimated radiation-induced secondary malignancy rates from the Biological Effects of Ionizing Radiation VII report with dose extrapolation using the linear no-threshold model – and found that the loss of life expectancy (LLE) ranged from 11.2 years in patients under age 40 to 3.9 years in patients over age 70. Effective CTU dose was 31.7 mSv.
The model specifically assessed the risk of an undiagnosed upper tract malignancy using renal ultrasound compared to LLE of secondary malignancy from CT Urography. For each of 4 subpopulations (male vs. female, <50 vs. >50), they identified a LLE threshold above which CTU would be superior to US. This ranged from 49 years (females, <50) to 1.07 years (men, >50). However, besides concluding that US may be better in “low-risk” populations, they don’t provide guidance on what the cutoffs for low and high-risk should be.
My take-home is that US should use more often as CTU is not benign. This should be strongly consider in younger patients, male or female. In old patients (>50), the benefit is less clear.
Limitations / Discussion Points:
1. Assumptions (even small changes) can change the model significantly
2. Many guidelines have already begun to advocate for US rather than CT
3. This model assumes a single CT scan – in reality, many patients get repeated hematuria evaluations!
Presenter: Todd Yecies, Resident in Urological Surgery at UPMC
Co-Authors: Jathin Bandari, Bruce Jacobs, Benjamin Davies
Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, Twitter: @tchandra_uromd at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA