The term Lower GI refers both to the final segment of the digestive system and to a common diagnostic medical procedure. The anatomical area encompasses the gastrointestinal tract responsible for the last stages of digestion and waste elimination. The diagnostic test, formally known as a Lower GI Series or Barium Enema, uses specialized imaging to visualize this internal structure. Physicians often request this procedure to investigate symptoms such as persistent changes in bowel habits, unexplained abdominal pain, or blood in the stool.
Anatomy and Function of the Lower GI Tract
The lower gastrointestinal tract is primarily composed of the large intestine, which includes the cecum, colon, rectum, and anus. This section begins where the small intestine ends, receiving the remaining liquid, undigested food waste. The large intestine is significantly wider than the small intestine, but it is much shorter in length.
The function of this tract is to convert liquid waste into solid stool. This is achieved through absorbing water and residual electrolytes, such as salts, from the material. Bacteria residing within the colon further break down certain nutrients and synthesize beneficial vitamins, including vitamin K.
The colon is divided into several segments—ascending, transverse, descending, and sigmoid—that propel the forming stool toward the rectum through muscular contractions called peristalsis. The rectum serves as a temporary storage vessel for the stool before it is finally eliminated from the body through the anus. Maintaining this balance of water absorption is important; too little results in diarrhea, while excessive absorption leads to constipation.
Understanding the Lower GI Procedure
The Lower GI Series, or Barium Enema, is an X-ray examination used to visualize the large intestine. The procedure is performed in a radiology department by a radiologist or a trained technologist. The goal is to detect structural abnormalities that may not be visible with standard imaging techniques.
The test utilizes a contrast agent, most commonly a white, chalky liquid called barium sulfate. The patient is positioned on an X-ray table, and a lubricated tube is gently inserted into the rectum. The barium is then carefully instilled through this tube, coating the inner lining of the colon.
The barium is an opaque substance that blocks X-rays, causing the filled colon to appear. During the filling process, the radiologist uses fluoroscopy, a continuous X-ray beam that creates a live video image on a monitor. The patient may be asked to change positions frequently, allowing the barium to evenly coat all surfaces of the colon.
In many cases, a double-contrast study is performed. Air is gently pumped into the colon after some barium has been expelled, which expands the colon and helps the remaining barium cling to the wall. This provides a more detailed view of the mucosal lining for identification of small lesions or polyps. Once the necessary images are captured, the tube is removed, and the patient is directed to expel the remaining barium.
Preparing for the Procedure and Recovery
Proper preparation is required, as the colon must be completely clear of any solid waste. Patients are instructed to follow a clear liquid diet for one to three days leading up to the procedure. This diet includes clear broth, plain tea or coffee, and strained fruit juices, while avoiding any liquids with red, blue, or purple coloring.
To ensure a clean colon, a thorough bowel preparation regimen is required, often involving a combination of oral laxatives and enemas taken the night before and possibly the morning of the test. Patients must also fast after midnight on the day of the procedure. These steps prevent residual stool from obscuring the X-ray images, which would necessitate repeating the procedure.
Immediately after the procedure, patients may experience mild abdominal cramping and bloating. Stools will appear white or light-colored for several days due to the residual barium passing through the digestive system. Patients should drink plenty of fluids to flush the remaining barium out of their system and prevent constipation. Patients should contact their healthcare provider immediately if they experience severe symptoms such as fever, severe abdominal pain, or an inability to pass gas.
Conditions Affecting the Lower GI
The Lower GI Series is a valuable diagnostic tool used to identify a range of conditions affecting the large intestine. One major category is Inflammatory Bowel Disease (IBD), which includes Ulcerative Colitis and Crohn’s disease.
The test can also detect diverticulitis, which occurs when small pouches, called diverticula, that form in the colon wall become inflamed or infected. The imaging can reveal the presence of polyps, which are small growths on the inner lining of the colon that can sometimes become cancerous. By visualizing the shape and structure of the colon, the procedure helps identify strictures, obstructions, and areas of abnormal growth, which are characteristic signs of colorectal cancer.