Long periods of fasting prior to contrast-enhanced CT, particularly restrictions on fluid intake, vary widely throughout the world, and may ultimately be unnecessary, according to a study published in the May issue of Radiology.

“The sheer number of the patients undergoing contrast-enhanced CT every day makes the question of whether a preparatory fast is necessary an important one,” wrote Bae-Young Lee, MD, of the Catholic University of Korea in Seoul, and colleagues. Despite the importance of the question, the authors noted that few articles in published literature have attempted to answer it, and their own institution has been divided on whether to maintain the practice of fasting.

The researchers conducted a literature review, looking for patients who developed aspiration pneumonia as a result of fluid ingestion prior to a contrast-enhanced CT exam, and a multinational survey of medical institutions was conducted to determine current practice with regard to fasting protocols for fluids and solids. Survey data were available from 69 institutions, comprised of Korean, American, French, Australian, German and Egyptian hospitals.

Based on the findings, concerns about adverse effects from drinking liquids prior to a CT exam seem to be unfounded as the authors were not able to find a single case of aspiration in any of the more than 2,000 patients found in the literature who underwent contrast-enhanced CT after fluid ingestion. The authors also noted that in recent years, there’s been an increase in so-called “hydro-CT”, in which a contrast-enhanced CT scan of the stomach is performed after a patient drinks water.

“The fact that there is no reported safety issue with hydro-CT makes it hard to justify routine fasting for contrast-enhanced CT, especially when imaging body parts such as the chest or liver with no oral administration of contrast medium,” wrote Lee and colleagues.

The survey revealed a wide variation in practice between hospitals and between countries. In general, fasting was longer in Korea and Egypt, and shorter in Germany and France. There was variation within each country, the most extreme example being Egypt’s solid fasting practices, which ranged from zero hours to overnight fasting. Fluid fasting remained common in the U.S.

Lee and colleagues determined that drinking clear fluids, tea or decaffeinated black coffee should be allowed without restriction or up to an hour prior to a contrast-enhanced CT. “With respect to solids, our recommendation is less clear-cut. Some radiologists may choose to follow the examples of the European countries and abandon dietary restriction entirely. Others, if still concerned that vomiting after food intake may complicate an act of resuscitation or may cause minor problems in patient handling, may choose to maintain or modify their restriction on solids while encouraging drinking of clear fluids during the fasting hours.”

Hospitals don’t necessarily need to overhaul their solid fasting policies; patients should still fast prior to contrast-enhanced CT exams of the abdomen and pelvis as they might be unwilling to drink oral contrast on a full stomach, according to the authors. Fluid fasting policies are more important, since lack of hydration can contribute to contrast material-induced nephropathy.

“Policies on fluid restriction prior to contrast-enhanced CT should be reconsidered and there is need for more definitive research on the subject,” concluded the authors.

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