Risk of Radiation from Computerized Tomography Urography in the Evaluation of Asymptomatic Microscopic Hematuria

The AUA (American Urological Association) guidelines for asymptomatic microscopic hematuria recommend that patients undergo computerized tomography urography, which is associated with high doses of ionizing radiation. To our knowledge the associated risk of secondary malignancy and mortality remains unknown. We modeled the risk of malignancy and associated mortality due to ionizing radiation from computerized tomography urography relative to the additional diagnostic benefit offered over renal ultrasound.

We performed a PubMed® based literature search to identify model inputs. We obtained estimates of age and gender specific radiation induced secondary malignancy and mortality rates from the BEIR (Biologic Effects of Ionizing Radiation) VII Phase 2 report with dose extrapolation using the linear no threshold model.

Patients with asymptomatic microscopic hematuria had a 0.053% and 0.48% prevalence of upper tract urothelial carcinoma and renal cell carcinoma, respectively. Ultrasound had 77% sensitivity for upper tract urothelial carcinoma and 82% sensitivity for renal cell carcinoma. The effective radiation dose of computerized tomography urography was 31.7 mSv. Based on these inputs a population of 100,000 patients with asymptomatic microscopic hematuria would include 53.1 and 478 patients with upper tract urothelial carcinoma and renal cell carcinoma, respectively. On ultrasound alone 98.2 cases of upper urinary tract malignancy would be missed. An additional 149 cases of secondary malignancy would be caused by computerized tomography urography associated radiation with 101 fatalities. A total of 1,018.3 computerized tomography urography studies would need to be performed to detect an additional case of upper tract malignancy.

Based on current risk models computerized tomography urography for asymptomatic microscopic hematuria may be associated with a small but significant risk of secondary malignancy relative to the additional diagnostic benefit offered.