A colonoscopy is an endoscopic procedure that allows a physician to look directly at the inner lining of the large intestine, which includes the colon and the rectum. Using a long, flexible tube equipped with a camera, the procedure provides a visual examination of the large bowel. It acts both as a primary screening method for asymptomatic individuals and as a detailed diagnostic tool for those experiencing symptoms.
Identifying Precancerous Polyps
The primary preventative power of a colonoscopy lies in its ability to detect and remove precancerous growths known as polyps. Polyps are small masses that form on the inner surface of the colon and rectum. While many polyps are harmless, others can develop into cancer over time.
Colonoscopy allows for the differentiation between non-threatening hyperplastic polyps and adenomatous polyps, which are considered the precursors to most colorectal cancers. Adenomas are glandular growths that exhibit dysplasia, meaning their cellular structure is abnormal. The procedure allows for immediate removal of these growths through a process called polypectomy, using instruments passed through the scope itself. This removal drastically reduces the risk of a lesion progressing to malignancy.
The characteristics of the removed polyps, such as size and type, dictate the schedule for future surveillance colonoscopies. For instance, advanced adenomas may require a shorter interval between follow-up procedures, while low-risk adenomas may permit a longer surveillance period, often five to ten years.
Detecting Colorectal Cancer
Beyond prevention, the colonoscopy is an effective method for detecting established, invasive colorectal cancer. During the examination, the physician can directly visualize masses, ulcerated lesions, or areas of thickened tissue that are suspicious for malignancy. Cancers appear as distinct growths that often bleed easily or have an irregular, firm appearance.
If a suspicious mass is found, the procedure allows for immediate biopsy, where a small tissue sample is collected using specialized forceps. This tissue is then sent to a laboratory for pathological examination to confirm the presence of cancer cells. Obtaining a biopsy is the definitive step for diagnosis, confirming whether the observed lesion is a benign mass or an invasive cancer requiring further treatment planning.
Diagnosing Inflammatory Bowel Disease
A colonoscopy is the preferred tool for diagnosing and monitoring chronic inflammatory bowel diseases (IBD), specifically Ulcerative Colitis (UC) and Crohn’s Disease. The procedure reveals characteristic patterns of inflammation that help physicians differentiate between the two conditions.
In Ulcerative Colitis, the inflammation typically begins in the rectum and extends continuously upward through the colon, affecting only the inner mucosal lining. Endoscopic signs include a diffuse, uniform redness, loss of the normal vascular pattern, and friability, where the tissue bleeds easily upon contact.
Crohn’s Disease, by contrast, is characterized by patchy areas of inflammation with segments of healthy tissue in between, known as skip lesions. Crohn’s inflammation often involves all layers of the intestinal wall (transmural involvement) and may present with deep ulcerations and a cobblestone appearance. The colonoscopy is utilized to assess the severity and extent of the inflammation, guiding treatment decisions and monitoring the disease’s response to therapy.
Revealing Structural and Vascular Issues
The visual inspection provided by colonoscopy can identify issues related to the colon’s structure and vasculature. One common finding is diverticulosis, which presents as small, outward-pouchings or sacs in the colon wall. Colonoscopy confirms their presence and location.
The procedure is also effective for locating the source of unexplained gastrointestinal bleeding. In many cases, this bleeding originates from angiodysplasia, which are small, abnormal clusters of blood vessels near the mucosal surface. These lesions appear as discrete, fern-like red spots. Once identified, the physician can apply thermal energy through the scope to cauterize the angiodysplasia and stop the bleeding.
Furthermore, colonoscopy can reveal strictures, which are narrowings or constrictions of the colon lumen. These strictures may be caused by scar tissue from previous episodes of diverticulitis, chronic inflammation from IBD, or other factors leading to obstruction. Direct visualization allows for assessment of the narrowing’s cause, and in some cases, the scope can be used to dilate the stricture.