Can a small bowel blockage be missed on a sb follow through? i know i have a mass of 13 yr old abdominal adhesions---can they mask a problem?

Yes and No: Adhesions cause obstructions by twisting the bowel like a kinked garden hose. Therefore, when the obstruction resolves, the x-rays will look entirely normal. A sbft is more useful for identifying intrinsic narrowing of the bowel that could occur due to tumors, strictures, etc.

Complex question: Here. Sbft exams can miss intestinal obstructions if they are intermittent or partial. Adhesions can cause problems and they will never go away unfortunately. I don't think the adhesions themselves would mask any problem, but the symptoms they produce might mask other conditions. Ask your surgeon or GI specialist for details.