Final answer:
A ruptured inferior vena cava is a likely cause for abdominal swelling observed after injecting the right common carotid artery with fluid, especially if fluid is not reaching the arms and legs.
Step-by-step explanation:
If you are injecting fluid into the right common carotid artery and noticing abdominal swelling, while at the same time you are not seeing fluid distribution in the arms and legs, it is possible that a major vessel has ruptured. Given the scenario, the inferior vena cava is a likely candidate for rupture because it carries blood from the lower limbs, pelvis, and abdomen back to the heart. If this vessel is damaged or nicks during the procedure, blood could leak into the abdominal cavity, resulting in swelling.
On the other hand, if there is a maldistribution specifically to the upper limbs and the head, theoretically, the superior vena cava could be implicated as well. However, given the route you have described (injection through the common carotid artery and drainage through the jugular vein), it is less likely compared to the inferior vena cava in the context of abdominal swelling.