Abstract
Consecutive adults scheduled to undergo abdominal CT with oral contrast were asked to choose between 1000 ml water only or positive oral contrast (50 ml Télébrix-Gastro diluted in 950 ml water). Two abdominal radiologists independently reviewed each scan for image quality of the abdomen, the diagnostic confidence per system (gastrointestinalsystem/organs/peritoneum/retroperitoneum/lymph nodes) and overall diagnostic confidence to address the clinical question (not able/partial able/fully able). Radiation exposure was extracted from dose reports. Differences between both groups were evaluated by Student’s t-test, Mann-Whitney-U-test or chi-square-test. Of the 320participants, 233chose water only. All baseline characteristics, image quality of the abdomen and the diagnostic confidence of the organs were comparable between groups and both observers. Diagnostic confidence in the water only group was more commonly scored as less than good by observer1. The results were as follows: the gastrointestinal system(18/233vs1/87; p = 0.031), peritoneum (21/233vs1/87; p = 0.012), retroperitoneum (11/233vs0/87; p = 0.040) and lymph nodes (11/233vs0/87; p = 0.040). These structures were scored as comparable between both groups by observer2. The diagnostic confidence to address the clinical question could be partially addressed in 6/233 vs 0/87 patients (p = 0.259). The water only group showed a tendency towards less radiation exposure. In summary, most scan ratings were comparable between positive contrast and water only, but slightly favored positive oral contrast for one reader for some abdominal structures. Therefore, water only can replace positive oral contrast in the majority of the outpatients scheduled to undergo an abdominal CT.
Highlights
CT protocols vary by institution, equipment, setting and clinical question
The justification of omitting oral contrast for emergency department patients has been questioned and extensively studied, leading to withholding oral contrast in these patients[2,3,4,5]. It is not clear whether the advantages of withholding oral contrast in the emergency department can be extrapolated to the outpatient setting, as they have different clinical questions and patient spectrum
To validate the hypothesis that water only as oral contrast is non-inferior to positive oral contrast preparation in abdominal CT, we performed a larger prospective study. The aim of this prospective study was to compare the image quality rating, diagnostic confidence per structure in the abdomen, overall diagnostic confidence to address the clinical question and radiation exposure between water only and positive contrast (Télébrix Gastro diluted in water) as oral contrast agent in outpatients undergoing abdominal CT
Summary
CT protocols vary by institution, equipment, setting and clinical question. the default abdominal CT protocol for outpatients regularly includes both oral contrast (either positive or negative) and an intravenous contrast administration. One study by Wang et al showed higher radiation exposure for scans performed with positive oral contrast than those with negative oral contrast in phantoms, respectively 8.7 ± 0.1 mGy, and 8.2 ± 0.2 mGy (6.1% higher than in water only, p = 0.02). To validate the hypothesis that water only as oral contrast is non-inferior to positive oral contrast preparation in abdominal CT, we performed a larger prospective study The aim of this prospective study was to compare the image quality rating, diagnostic confidence per structure in the abdomen, overall diagnostic confidence to address the clinical question and radiation exposure between water only and positive contrast (Télébrix Gastro diluted in water) as oral contrast agent in outpatients undergoing abdominal CT
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