A lower endoscopy is a medical procedure used to examine the lining of the large intestine, including the colon and the rectum. This examination is a primary tool for both diagnosing and screening various conditions affecting the lower digestive tract. By providing a direct, magnified view of the intestinal wall, the procedure allows physicians to detect subtle changes, take tissue samples, and often treat abnormalities during the same session. This ability to visualize and intervene makes lower endoscopy a fundamental part of gastroenterological care.
Understanding the Lower Endoscopy Procedure
The term “lower endoscopy” primarily refers to two distinct procedures: the colonoscopy and the flexible sigmoidoscopy. Both involve inserting a long, flexible tube (endoscope) through the rectum. This instrument is equipped with a camera, a light source, and channels for surgical tools, allowing for detailed visualization and intervention.
The key difference lies in the extent of the examination within the large intestine. A colonoscopy is the more comprehensive procedure, designed to examine the entire length of the colon, from the rectum up to the cecum. In contrast, a flexible sigmoidoscopy only inspects the lower portion of the large intestine, specifically the rectum and the sigmoid colon.
Because a sigmoidoscopy covers a smaller area, it requires less intensive bowel preparation and may be performed without deep sedation. For both procedures, the physician uses the scope to look for lesions, inflammation, or structural changes. If an abnormal area is found, the scope’s working channels allow for the collection of a biopsy (tissue sample) and the performance of minor therapeutic actions.
Identifying Precancerous Growths and Cancer
One of the most significant applications of lower endoscopy is in the screening and prevention of colorectal carcinoma. Colorectal cancer frequently develops from small, non-cancerous growths called polyps. The detection and removal of these growths is a major focus of screening colonoscopies.
The majority of polyps that have the potential to turn cancerous are known as adenomatous polyps, which can take years to progress into malignant tumors. During a colonoscopy, the physician identifies these polyps, which appear as raised or flattened lesions. Once located, a procedure called a polypectomy involves removing the growth entirely using snares or specialized forceps passed through the endoscope.
If a suspicious lesion is too large to be removed safely or appears to be cancerous, the endoscope allows for a targeted biopsy. The tissue is then analyzed by a pathologist to confirm the presence and type of colorectal carcinoma, which guides subsequent treatment decisions.
Diagnosing Chronic Inflammatory Conditions
Lower endoscopy is an indispensable tool for the diagnosis and management of Inflammatory Bowel Diseases (IBD), which includes Ulcerative Colitis (UC) and Crohn’s Disease. The procedure allows physicians to directly visualize the distinct patterns of inflammation characteristic of each condition. Biopsies taken during the examination provide cellular-level confirmation of the diagnosis and help rule out other potential causes of inflammation, such as infections.
In Ulcerative Colitis, the inflammation is continuous and superficial, starting in the rectum and extending proximally through the colon. Endoscopic findings often show a diffuse pattern of redness, loss of the normal vascular pattern, and friability (tissue bleeds easily upon contact). This continuous nature and mucosal-layer involvement are distinguishing features of UC.
Crohn’s Disease presents a different visual pattern, often characterized by patchy, non-continuous inflammation, sometimes referred to as “skip lesions.” The inflammation in Crohn’s is also transmural, meaning it affects the entire thickness of the intestinal wall, leading to deep, linear ulcers and the potential formation of strictures, or narrowings. The ability to see the distribution and depth of these lesions allows the physician to differentiate between the two types of IBD and assess the severity and extent of the disease.
Detecting Sources of Bleeding and Structural Issues
Beyond cancer screening and IBD diagnosis, lower endoscopy investigates the source of unexplained bleeding from the lower gastrointestinal tract. Seeing the mucosal lining in real-time makes it highly effective for pinpointing the exact origin of blood loss. In many cases, the procedure offers therapeutic capabilities to stop the bleeding immediately.
One common finding is diverticular disease, where small pouches (diverticula) bulge outward from the colon wall. Bleeding can occur if a small blood vessel near the pouch erodes. Another source of bleeding is angiodysplasia, which are small, fragile clusters of dilated blood vessels.
For both diverticular bleeding and angiodysplasia, the endoscope allows the physician to apply direct treatment, such as cauterization or the injection of hemostatic agents, to seal the bleeding vessel. The procedure can also identify common causes of rectal bleeding, such as internal hemorrhoids or anal fissures, and visualize structural changes like strictures or fistulas.