Patient 1 has a relatively normal gas pattern, and is a good demonstration of the normal folds of the colon, called haustra.

Patient 2 has two stacked small bowel loops with folds that look too far apart and thickened. This is worrisome for edema.

patient 1

patient 2

When identifying colon on an abdominal radiograph, look for the typical scalloped margin where the bowel protrudes between the haustra, which are relatively far apart and unevenly spaced. When you see two or more loops stacked on top of one another in a horizontal orientation, this is very suggestive of small bowel, since the colon does not follow such a course through the abdomen. When an obstruction has been going on for a while, the involved bowel can become edematous, and this is a worrisome sign since it can indicate inflammation or ischemia.