If a doc orders a ct scan on abdomin. wouldn't it be the entire stomach? including in it the liver lungs etc. and would it catch tb?

Not necessarily: An abdominal ct scan would show the bases of the lungs, but may or may not show tuberculosis if there were no granulomas in the bases.

Lungs not visualized: An abdominal ct scan generally visualized everything from the diaphragm down to the pelvis. They often view a bit of the bottoms of the lungs, but they don't view a significant amount of lung tissue. Therefore, an abdominal ct would not be useful for diagnosing pulmonary (lung) tb.

Skin test: If you are concerned about TB exposure, I would recommend a ppd skin test. If it is positive, then a chest radiograph is ordered. Usually your local public health department can provide the screening or most primary health providers.