When would you use an upper/lower gi series instead of endoscopy/colonoscopy?

Fnctionl vs physical: The UGI can add evidence of the "function" of the GI tract vs. The physical features seen on scope. One may see evidence of active reflux or watch the process of swallowing and the timing of gastric emptying. The small bowel follow thru goes beyond where a scope can see giving the doctor info about the small intestine. Also it may be used in someone too sick to tolerate a scope proceedure.

Too sick: If you were too sick for the 2 procedures i.e. Severe end-stage COPD would put you at risk for the sedation or severe blood abnormalities in which case the non-invasiveness of both GI series would make those 2 tests more attractive. Also, sometimes endoscopes are not physically able to be performed due to anatomical variations. Gi aries could get around this problem.