Vet Found Possible Mass Near Spleen on X-Ray - Looking for General Input

My 5-year-old mixed breed dog, Reese, went to the vet yesterday for moderate GI upset. He had vomited twice the night before and was showing signs of nausea (licking the floor, trying to eat random things, etc.).

His veterinarian said we could either treat symptomatically with medications or do abdominal X-rays to make sure there wasn’t an obstruction. We opted for the X-rays. She noted that there was quite a bit of gas in his intestines and that some intestinal loops appeared slightly twisted/displaced, but she did not see any obvious obstruction. She advised us to go to urgent care if he vomits again.

While reviewing the X-rays, she also noticed a gray soft-tissue opacity near the spleen. She said it could potentially be fat, but it could also be a mass, and she recommended an abdominal ultrasound with a specialist for further evaluation. I have already contacted the specialist she referred us to and am currently waiting for an appointment.

Since starting his GI medications, he seems much better. He’s eating, acting more like himself, and has not vomited again. However, I’m understandably very anxious about the finding near the spleen.

I know no one can diagnose from an X-ray alone, but I’d appreciate any thoughts on what this could potentially be and whether the appearance is more consistent with fat, a benign finding, or something more concerning. We’re keeping him calm and monitoring him closely until the ultrasound in case there is any risk of rupture or other complications.

X-rays: https://imgur.com/a/dckb7QV

Thank you for any insight.