Reducing radiation dose in diagnostic CT of the abdomen

Here’s a neat trick for dose reduction in appendicitis CT cases – which often are done in young patients.

It falls into the general category of only scanning as much Z-axis length as is needed to address a given indication –  and no more.

Time Saved Does Not Justify Inaccuracy

A recent article on discusses situations where physicians may “bend the truth” in order to arrive at quicker results – in this case, the decision to perform an appendectomy.

CT scanning without oral contrast for possible appendicitis gives up several percentage points in accuracy. A radiologist may mistake a non-contrasted terminal ileum for an inflamed appendix. And the earliest sign of appendicitis is called the arrowhead sign, which is contrast in an edematous appendiceal orifice – cannot be detected without the contrast. Many surgeons take comfort from the presence of contrast in the appendix as evidence that portion of the appendix is not obstructed and inflamed.

Sure you can cut corners and save time. The ultimate time-saving corner to cut is to not do a CT and just decide based on physical exam plus lab results. The accuracy of CT without contrast is similar to that approach. But if we do CT in order to get more accurate diagnosis, we need to have the CT do its best job in terms of accuracy… which requires oral contrast.

In my opinion, the time saved by doing CT without oral contrast definitely does not justify the loss in accuracy. Pressure to practice this way comes from well intentioned folks who do not have to interpret CT exams themselves, and stand by the results.