Final answer:
A small bowel follow-through is considered complete when the contrast reaches the cecum, marking the transition from the small to the large intestine.
Step-by-step explanation:
To determine when a follow-through of the small bowel is complete, we look for when the contrast reaches the cecum. This is because the cecum marks the beginning of the large intestine and indicates that the contrast material has passed through the entire small intestine. Discomfort reported by the patient, the elapse of a predetermined time, or the decision of the technologist are not definitive indicators of the completion of a small bowel follow-through. Once the contrast material enters the large intestine, it begins mixing with the existing contents, which have become more solid, eventually forming feces that will be expelled through the rectum.