Contrast medium in abdominal radiography – Do you have to take survey radiographs?

One of the freshman students asked a good question today. Can you ever just start a contrast study in the abdomen without doing survey radiographs first?

It’s tempting; why waste two radiographs when you know you need contrast?
There are several reasons why survey films are necessary, and you’ll always be glad you have them.

First of all, you probably need some type of imaging study to determine what the problem is. Abdominal radiographs are a good place to start, because they give you a good overview. Depending on the animal’s problem, you might pick up pneumothorax, or a fracture that you didn’t expect. There may also be additional abdominal findings other than the one you wish to confirm that will help guide your approach to the case. For example, if you are considering an upper GI in a vomiting dog, the presence of an obvious obstructive pattern or free gas in the abdomen means that the upper GI is uneccesary. Things can change in the period of time since the previous set of radiographs.If you had decided to ultrasound the animal first, and then use contrast to confirm your suspicion of a ruptured ureter or bladder, there are still reasons for surveys. Pre-contrast radiographs allow you to adjust the technique and positioning before starting the contrast study. Once you administer contrast, you might have a finite time to get good images such as during urethral distension in a urethrogram, or to see contrast leaking from a ruptured bladder during injection. Missing that critical time point because of poor technique can make your study non-diagnostic. Contrast radiography also requires an increased technique than on your regular technique chart, to compensate for the density of the contrast medium. It’s also good to know if the colon or bladder are full and will obscure your view of the organ of interest.

Finally, before and after images can be really useful. In subtle changes like a small leak from the urinary bladder, a gradual opacification of the peritoneal space can be hard to pick up. Having a comparison to a non-contrast image helps to make that distinction.

Reasons for taking survey radiographs before administering contrast:

Adjust technique and positioning

Confirm adequate preparation of the abdomen (colon and bladder)

Diagnose additional and unexpected problems

Confirm that contrast study is indicated

Pre- and post-contrast comparisons