Fasting is not necessary before undergoing a contrast-enhanced CT exam, according to a new study published Friday. The practice may actually do more harm than good.
Traditionally, patients have been told not to eat prior to contrast-enhanced imaging exams in order to avoid adverse reactions, such as nausea and vomiting, which are common. But nausea cases actually dropped after eliminating these instructions, with no change in vomiting incidents, experts detailed in Insights into Imaging.[1]
“Instructions to fast for several hours prior to administration of contrast media were considered essential, and this policy has traditionally been kept due to concerns about vomiting and its potential to cause aspiration,” Yoshito Tsushima, with Gunma University’s Department of Diagnostic Radiology and Nuclear Medicine in Japan, and colleagues wrote. “Our current study, along with previous studies, has confirmed not only the lack of benefit but also the possible disadvantages of fasting prior to contrast-enhanced CT.”
Tsushima et al. eliminated restrictions on eating solid foods prior to contrast CT in March 2019. They then compared the incidence of acute adverse reactions that occurred from December 2015 through November 2018 to those between April 2019 and March 2020.
After going over medical records, the researchers found the overall number of adverse reactions did not significantly change, tallying 705 cases before the intervention and 205 afterward. Incidence of nausea did experience a meaningful drop, however, from 0.31% to 0.18%, they noted.
The exact reason for this decline is unknown. But over fasting — including limiting fluid intake — they hypothesized, may cause patients to feel sick and lead to nausea and dehydration.
Additionally, vomiting cases stayed level and zero cases of aspiration pneumonia were reported. Severe allergic reactions also remained similar.
Fasting should only be recommended before certain exams, the researchers explained, including virtual gastroscopy and colonoscopy, 3D anatomic reconstruction for preoperative planning, and examinations performed under general anesthesia or sedation.
“The current study provided no direct evidence suggesting that fasting prior to contrast-enhanced CT prevented vomiting, and no aspiration pneumonia attributable to vomiting was observed,” the authors concluded. “The significantly decreased incidence of nausea may decrease patient discomfort. Our study confirmed that fasting is not required prior to CT examination with non-ionic low-osmolar iodinated contrast media.”
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Matt joined Chicago’s TriMed team in 2018 covering all areas of health imaging after two years reporting on the hospital field. He holds a bachelor’s in English from UIC, and enjoys a good cup of coffee and an interesting documentary.