It's just the description of what they did. Arterial phase means the contrast (dye that shows up in blood vessels on CT) was in the arteries when they captured the image.

As noted below, the radiologist saw no masses which means he didn't see cancer. Radiologists look at hundreds of Ct scans per week and are very well trained. When he says no masses, I'd trust him. He knows the machine and the type of test that was run, and he's pretty clear about that. The radiologist said he thought you had gastritis (irritation of the digestive track, i.e., upset stomach). This will absolutely explain your symptoms and you should accept that.

Also, a "low" lipase is absolutely insignificant. There is not need to worry about it. The values the lab uses to decide what is low or normal is they take thousands of healthy patients and measure their lipase. Then they use fancy math to figure out what range of values most people have. And they say that's normal. However, many of these people will have values either above or below the normal range and they're still healthy.

As physicians,we rely on the entire picture to make diagnosis since we know many values maybe outside the "normal" range. Trust your doctor.