Evaluation of the Risks and Benefits of CT Urography for Assessment of Gross Hematuria
Guidelines for evaluation of gross hematuria recommend that patients undergo CT Urography (CTU), which is associated with a high dose of ionizing radiation. No current studies have compared the estimated risk of secondary malignancy from CTU with the benefits of cancer detection when compared to renal ultrasound.
A PUBMED-based literature search was performed to identify model inputs, specifically detection rates of upper tract malignancy in gross hematuria patients stratified by age and gender, age and gender distribution of gross hematuria patients, sensitivity of renal ultrasound for detection of upper tract malignancy, loss of life expectancy from a secondary malignancy diagnosis, and CTU effective radiation dose. Estimates of radiation-induced secondary malignancy rates were obtained from the Biological Effects of Ionizing Radiation VII report with dose extrapolation using the linear no-threshold model.
Patients with gross hematuria have a prevalence of upper tract urothelial carcinoma and renal cell carcinoma of 0.63% and 1.2%, respectively. Male gender and age over 50 years were associated with a relative risk of upper tract malignancy of 2.04 and 9.75, respectively. Renal ultrasound has a sensitivity of 77% for upper tract urothelial carcinoma and 82% for renal cell carcinoma. The estimated loss of life expectancy from a radiation-induced secondary malignancy ranged from 11.2 years in patients under 40 to 3.9 years in patients over 70. Effective radiation dose of CTU was found to be 31.7 mSv. Based on these inputs, the risks of an upper tract malignancy that would be undiagnosed on renal ultrasound was identified for each sub-population and compared to the risks of secondary malignancy from CTU. Because the loss of life expectancy from an undiagnosed upper tract malignancy is unknown, the threshold value of this unknown above which the loss of life expectancy from CTU is less than the loss of life expectancy from ultrasound was identified (Table 1). This ranged from 49.17 years in females under 50 to 1.07 years in males over 50.
This model suggests that in low-risk patients, CTU for evaluation of gross hematuria may carry a significant risk of radiation-induced secondary malignancy relative to the number of additional cases of upper tract malignancy detected.