How is use of upright KUB in acute abdomen?

● First test done to search for intestinal occlusion or ileus. ● KUB upright shows us air fluid level in the intestine if there is occlusion. Note: air fluid level is a pattern that shows on x-ray due to both fluid and gas collection. Air rises above fluid and there’s a flat surface at the “air-fluid” interface. ● How do we know if the occlusion is in the small intestine or colon? We do so by 3 markers: a. In SI (small intestine) we have complete circular folds while in colon we have semi-circular folds (do not complete the circumference), b. SI is in central region of abdomen while colon is in lateral region. c. Air fluid level in SI is larger than high (more width than height) while it is the opposite for colon (higher than wide).