A lower gastrointestinal series, also called a barium enema, is a medical procedure used to examine and diagnose problems with the human colon (large intestine). X-ray pictures are taken while barium fills the colon via the rectum.

This test may be done in a hospital or clinic radiology department. The patient lies on the X-ray table and a preliminary X-ray is taken. The patient is then asked to lie on the side while a well lubricated enema tube is inserted into the rectum. As the enema enters the body, the patient might have the sensation that their stomach is being filled. The barium is then allowed to flow into the colon. A small balloon at the tip of the enema tube may be inflated to help keep the barium inside. The flow of the barium is monitored by the health care provider on an X-ray fluoroscope screen (like a TV monitor). Air may be puffed into the colon to distend it and provide better images (often called a "double-contrast" exam). The patient is usually asked to move to different positions and the table is slightly tipped to get different views.