Computed tomographic enterography is a noninvasive method that can be used to accurately evaluate small bowel lesions and extraenteric structures.1 It is performed by dilating the lumen of the gastrointestinal tract with an orally administered contrast agent and then enhancing the intestinal wall and mesenteric vessels by IV administration of a contrast agent. Protocols for CT enterography have been evaluated in humans with regard to contrast agents (type, dose, dilution ratio, and administration method), drugs for modulating gastrointestinal motility, IV administration of contrast agent (concentration and dose), and scan timing.1–6 In veterinary medicine, only a few studies2,7–9 have been performed with CT enterography, and those studies focused on the volume of orally administered contrast agent or scan timing.
For CT enterography in humans, the mural contrast enhancement pattern, length and location of lesions in the small bowel wall, and involvement of mesenteric vessels are usually assessed.3,10 When obscure gastrointestinal bleeding, bowel stricture, and vascular occlusion such as a thrombus or small bowel neoplasia are suspected, mesenteric circulation and enhancement of the small bowel wall are evaluated. In general, mesenteric circulation is assessed in the arterial phase to determine the degree of enhancement, distribution, and visualization of vascular branches, whereas enhancement of the small bowel wall is evaluated in the venous phase.3,10,11
A split-bolus technique combines the arterial and venous phases into 1 CT image after the total dose of the contrast agent is split and administered as 2 injections. This technique decreases radiation exposure to the patient and reduces the total number of CT images that must be interpreted, compared with radiation exposure and the number of images required for dual-phase scanning.12–16 Split-bolus techniques have not been widely applied in CT enterography, even in human medicine. However, in a retrospective study16 of 66 humans with active inflammatory bowel diseases, this technique allowed a significantly higher rate of detection of mucosal hyperenhancement, compared with the detection rate for single-injection CT enterography.
The purpose of the study reported here was to investigate the use of split-bolus CT enterography for the evaluation of the intestinal wall and mesenteric vessels in healthy dogs. We hypothesized that split-bolus CT enterography could be performed in dogs and would provide enhancement of the small intestinal wall and mesenteric vessels similar to that of dual-phase CT enterography.
Supported by the Animal Medical Institute of Chonnam National University and the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT, and Future Planning (grant No. NRF-2018R1A2B6006775).
The authors declare that there were no conflicts of interest.
Colyte, Taejoon Pharmaceutical Co, Seoul, Republic of Korea.
Alfaxane, Jurox Pty Ltd, Rutherford, NSW, Australia.
Terrell, Piramal Critical Care, Bethlehem, Pa.
Buscopan, Labiana Life Sciences, Barcelona, Spain.
Siemens Emotion 16, Siemens, Forchheim, Germany.
Omnipaque 300, GE Healthcare, Oslo, Norway.
Medrad Vistron CT injection system, Medrad Inc, Warrendale, Pa.
CARE Bolus, Siemens Medical Systems, Berlin, Germany.
Infinitt PACS, Infinitt Healthcare Co, Seoul, Republic of Korea.
IBM SPSS statistics, version 21, IBM Corp, Armonk, NY.
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Parameters for performance of CT enterography in dogs by use of 3 techniques.
|Variable||Dual phase||Split||Split-bolus tracking|
|No. of contrast CT scans||3||2||1|
|Test bolus||Injected||Injected||Not injected|
|Iohexol dose (mg of 1/kg)|
|Ratio of split contrast agent doses||—||60:40||60:40|
|Initiation of CT scan||Based on arterial scan delay and venous scan delay||When arterial scan delay and venous scan delay matched||When trigger point reached 100 HU|
— = Not applicable.
Scoring system used for qualitative evaluation of CT enterography in dogs.
|Visibility of peripheral vascularity||Only arcade vascularity visible; vasa recta vascularity not visible||1|
|Arcade and vasa recta vascularity somewhat visible, compared with in the intestine||2|
|Arcade and vasa recta vascularity markedly visible, compared with in the intestine||3|
|Enhancement of intestinal wall||Enhancement of artery only; no enhancement of intestinal wall||1|
|Enhancement of mucosal layer only||2|
|Transmural enhancement including entire intestinal wall||3|
|Transmural enhancement with marked mucosal enhancement||4|
|Image quality||CT images difficult to interpret because of artifacts||1|
|Moderately good CT images with some artifacts||2|
|Optimal CT images with few or no artifacts||3|
The arcade represented an arch-like structure of the cranial mesenteric artery created by a series of anastomosing arterial branches in the mesentery, and the vasa recta represented straight arteries arising from the arcades.