Flexible sigmoidoscopy and colonoscopy are medical procedures used to inspect the large intestine. Understanding the distinctions between these common examinations is important for individuals considering screening or diagnostic evaluations. This article clarifies their differences to help you understand which procedure might be recommended.
Flexible Sigmoidoscopy Explained
A flexible sigmoidoscopy involves a sigmoidoscope, a thin, flexible tube equipped with a light and a small camera at its tip. This instrument is guided through the rectum into the lower large intestine. It examines the rectum, sigmoid colon, and often a portion of the descending colon.
It investigates symptoms like rectal bleeding, changes in bowel habits, or lower abdominal pain. It also screens for polyps—small growths on the inner lining of the colon—or early signs of cancer in these lower regions. If polyps or abnormal tissues are found, samples can be collected for analysis, and small polyps may be removed.
Colonoscopy Explained
A colonoscopy uses a longer, flexible tube with a camera, called a colonoscope. This allows for a more extensive examination. The colonoscope is advanced through the entire large intestine, from the rectum to the cecum, which marks the beginning of the colon where it connects to the small intestine.
This comprehensive examination screens for colorectal cancer throughout the entire colon. It also identifies and removes polyps that could develop into cancer anywhere in the large intestine. A colonoscopy also investigates symptoms originating from any part of the large bowel, such as persistent abdominal pain, unexplained diarrhea, or chronic rectal bleeding.
Key Distinctions
The most significant difference between the two procedures is the scope of examination: flexible sigmoidoscopy inspects only the rectum and lower colon, while colonoscopy examines the entire large intestine. This allows colonoscopy to detect abnormalities, including polyps and cancers, in the upper colon that a sigmoidoscopy cannot reach.
Preparation also differs considerably. Flexible sigmoidoscopy requires a less extensive bowel cleanse, often one or two enemas shortly before the procedure. Colonoscopy requires a full bowel preparation, usually a clear liquid diet for one to three days and large volumes of laxative solutions to empty the colon.
Flexible sigmoidoscopy is often performed without sedation or with minimal light sedation, allowing most individuals to return to normal activities relatively quickly. Colonoscopy usually involves moderate to deep sedation or anesthesia for comfort during the longer examination, requiring a recovery period and often assistance for transportation home.
When it comes to polyp detection and removal, both procedures can identify polyps within their respective scopes of examination. Colonoscopy can find and remove polyps throughout the entire colon in a single procedure, a significant advantage for comprehensive screening. If a sigmoidoscopy reveals polyps or suspicious findings, a full colonoscopy may be recommended to check the rest of the colon.
Screening guidelines also differentiate their roles. Flexible sigmoidoscopy may be recommended for targeted lower colon screening, often every five years, especially when combined with annual stool tests. Colonoscopy is widely used for comprehensive colorectal cancer screening, typically recommended every 10 years for individuals at average risk, starting around age 45 or 50.
Both procedures carry low risks, which vary slightly. Potential risks include bleeding, particularly if polyps are removed, and a rare chance of perforation, which is a tear in the colon wall. While these risks are generally low for both, colonoscopy’s more extensive nature means a slightly higher, though minimal, risk profile compared to a sigmoidoscopy. Recovery after sigmoidoscopy is usually immediate, with some mild bloating or cramping. After colonoscopy with sedation, recovery involves a period of drowsiness, typically lasting a few hours, before returning to normal activities.