Answer to Question #3372 Submitted to "Ask the Experts"

Q

I am a 36-year-old female who recently had a barium enema (BE) procedure to evaluate constipation, and I am reassured by your experts' replies to others regarding diagnostic radiation, which is a subject that does frighten me, perhaps irrationally. It is also reassuring to see that many other women have felt similar anxiety about pelvic exposure during their childbearing years. My experience was also anxiety provoking because I got the feeling the referring physician was very uncomfortable answering my questions about the amount of radiation exposure the procedure would entail. Several days after I called his office to inquire about this issue, I got a return message stating that the procedure was routine and that there was "little, if any radiation involved." I recognize that he likely wanted to be reassuring more than technically accurate, but this response seemed a bit dismissive to me. The radiologist was able to answer my questions more thoroughly, and stated she would try to minimize the amount of exposure. She stated that a single-contrast BE, which my primary doctor requested, is lower exposure than double-contrast would be. My questions are: (1) Do referring physicians need to have a greater awareness of the radiation exposure involved in diagnostic procedures they recommend? (2) What is the difference between a single-contrast and double-contrast BE and do they indeed have different effective doses? (3) I gather from your answers to other questions that pelvic exposure prior to conception shouldn't meaningfully affect fertility and risk to offspring—am I correct? (4) As regards cancer risks, is lifetime exposure to ionizing radiation cumulative in its effects and does choosing a radiological procedure over a nonradiological alternative "exhaust" the amount of exposure that might be needed for some "more important" referral question in the future?

A

Referring to questions listed above, my answers are as follows.

1. This is an excellent question. It would be nice if referring physicians had a better idea of the radiation exposure associated with each x-ray procedure that they order. In the real world, they do not. The medical-school curriculum focuses more on the types of information that can be obtained from the procedures and the correct procedures to order for specific conditions rather than on the radiation exposure involved. When it comes to the radiation exposure involved with each procedure, they defer to their colleagues, the radiologists, who are specialists in that area. For the results of a recent study on this subject, see a BMJ (British Medical Journal) article.
    
2. A single contrast barium enema (BE) involves filling the large bowel with barium and obtaining all images with the large bowel full of barium. For a double contrast BE, the large bowel is filled with barium and then drained. Air is then pumped in to inflate the colon while its lining is still coated with barium. This method gives a more detailed view of the lumen or inside surface of the colon. Since there is less barium in a double contrast BE study, lower x-ray technique factors can be used and the dose is lower than for a straight barium enema study.
    
3. From all studies to date, including those of the A-bomb survivors from Hiroshima and Nagasaki, it appears that parental exposure to radiation does not lead to adverse pregnancy outcomes. For additional information, please see a National Radiological Protection Board (United Kingdom) Report.
    
4. In general, we assume that each dose of radiation presents us with some level of risk over the remainder of our lifetime and that each subsequent exposure adds to that risk. Surprisingly, there is not a clear understanding of the risk associated with low doses of radiation, such as the doses received from today’s routine diagnostic x-ray procedures, the reasons being that the risks are so small that they are not seen even when large populations are studied. Rather than being alarming, this should be reassuring. Procedures that involve nonionizing radiation (for example, ultrasound or MRI) might, or might not, be the best procedure for your particular symptoms. Your physician, in consultation with a radiologist, is the best person to recommend the procedure or procedures that are right for you based on your particular signs and symptoms.

Kenneth L. Miller, CHP, CMHP