The Harms of Hematuria Evaluation: Modeling the Risk-Benefit of Using Split Bolus Computerized Tomography Urography to Reduce Radiation Exposure in a Theoretical Cohort

Purpose: Computerized tomography urography is used to evaluate patients with gross or microscopic hematuria. Computerized tomography urography is a high radiation dose scan and, thus, it confers a higher risk of secondary malignancy. A computerized tomography urography split bolus protocol reduces radiation exposure but it may reduce sensitivity. In this study we used a theoretical cohort of patients with hematuria in which to model the risk of missing malignancies against the benefit of averting secondary malignancies.

Materials and methods: We calculated the prevalence of renal cell carcinoma and upper tract urothelial carcinoma in patients with hematuria by pooled analysis of cohort studies, which in conjunction with split bolus sensitivity allows for the estimation of missed malignancies. The number of prevented secondary malignancies was calculated from lifetime attributable risk estimates. Sensitivity analyses were run to determine the minimum sensitivity required for a net population benefit.

Results: Estimates of split bolus computerized tomography urography sensitivity ranged from 80% to 100% (mean 95.2%). At the low estimate of 80% sensitivity split bolus computerized tomography urography was beneficial in men and women with microscopic hematuria at ages less than 50 and less than 60 years, respectively. An increase in sensitivity to 90% improved the benefit 1 decade in each gender, representing 68.8% of patients with microscopic hematuria. The overall population of patients with microscopic hematuria benefited from split bolus computerized tomography urography at 91.1% sensitivity. However, in patients with gross hematuria the threshold for an overall population benefit was high at 98.4% sensitivity.

Conclusions: Exposure to ionizing radiation risks causing secondary malignancy. These data indicate that split bolus computerized tomography urography may be performed safely in 70% of the population of patients with microscopic hematuria. However, it is not currently advisable in patients with gross hematuria or in other patients at high risk.