Answer to Question #4762 Submitted to "Ask the Experts"

Recently, I had blood in my urine and was admitted to the local hospital emergency room (ER). The ER doctor ordered a CT of my abdomen with no dye. Then he ordered another scan, this time with the dye. I've talked to the CT scan technician and he told me that I received 24.47 mSv. Do I now have the risk of cancer or am I at risk of developing some other problem related to the high radiation exposure? Also, could this cause mutations in my sperm?

I'm sorry you are concerned about the radiation levels received from your CT scans, but the radiation levels used for this type of diagnostic study are well below the levels known to cause significant mutations in sperm, elevated cancer, or other radiation-related risks.

Theoretically, and assuming the linear no-threshold (LNT) hypothesis, any radiation exposure may contribute to an elevation of these risks. However, from a practical viewpoint at the dose levels you received, we cannot scientifically prove these excess risks.¹

The effects you describe are attributed to acute radiation exposures, but have only been observed at levels of radiation more than 100 times greater than what you received. If you wish to learn more about ionizing radiation, I would suggest the "Ionizing Radiation" article at Wikipedia. As noted in this article, you are always exposed to radiation from natural sources, and life on earth has evolved natural mechanisms within the body to cope with the effects of this natural radiation exposure. People in the United States receive, on average, about 3.6 mSv annually and, in some areas of the world, natural radiation levels have been measured as high as 260 mSv/yr. The people who live in these areas receive radiation levels approximately equivalent to 10 CT scans each year of their lives. However, we cannot demonstrate that they have significantly different cancer or mutation rates from populations living in low-background-radiation areas.

Any use of radiation in medicine has to be justified by the risk-to-benefit ratio for the procedure. The risk from two CT scans of 24.47 mSv each is very small when compared to the medical benefits you received by having the exam performed.² The symptom of blood in the urine is common, but it is also not normal. It can be a sign of an infection, kidney stones, cancer, blood-clotting disorders, and many other serious conditions. A CT scan with contrast is considered normal standard of care for this symptom. In fact, if you went to a hospital that didn't perform a CT scan after observing your symptoms, it would be subject to criticism for not providing the level of care expected from U.S. hospitals.

Please see the Medicine Consumer Health Web site and specifically the second reference that describes the routine tests performed for your condition: "Blood in the Urine Overview" and "Blood in the Urine Exams and Tests."

In your case, the diagnostic benefits outweigh greatly the small radiological risks incurred from the CT scan.

Mike Bohan
Radiation Safety Officer


Editor's notes:

¹Health Physics Society's Position Paper: Radiation Risk in Perspective August 2004. 

²Health Physics Society's Ask the Experts Feature, Medical and Dental Patient Issues: Risk/Benefit of Medical Radiation Exposures.