Endoscopy and colonoscopy are not the same thing, but a colonoscopy is a type of endoscopy. “Endoscopy” is an umbrella term for any procedure that uses a thin, flexible, lighted tube with a camera to look inside the body. A colonoscopy is one specific kind of endoscopy that examines the large intestine. When most people say “endoscopy” without any qualifier, they usually mean an upper endoscopy, which looks at the throat, stomach, and the first part of the small intestine.
How the Two Procedures Differ
An upper endoscopy (sometimes called an EGD) involves passing a scope through your mouth and down your throat. It travels through your esophagus, stomach, and into the duodenum, the first section of the small intestine. The scope used for this is relatively slim, typically under 10 mm in diameter.
A colonoscopy goes in from the other end. A scope is inserted through the rectum and advanced through the entire large intestine. Because it needs to navigate the curves and length of the colon, a colonoscope is longer than a gastroscope and can bend more, up to 270 degrees compared to the gastroscope’s 180 degrees. During the procedure, air is blown into the bowel to give the doctor a clear view of the lining.
Why Each One Is Ordered
Upper endoscopy is used to investigate symptoms in the upper digestive tract: persistent acid reflux, difficulty swallowing, unexplained nausea or vomiting, upper abdominal pain, or bleeding from the upper GI tract. It can diagnose conditions like GERD, esophageal motility disorders, and esophageal cancer. Doctors can also take tissue samples or remove polyps from the esophagus during the procedure.
Colonoscopy focuses on the colon and rectum. It’s used to evaluate chronic diarrhea, constipation, rectal bleeding, or lower abdominal pain. Polyps found during a colonoscopy can be removed on the spot, which is important because some polyps can develop into colon cancer over time. Colonoscopy also serves as the gold standard for routine colorectal cancer screening. The U.S. Preventive Services Task Force recommends screening starting at age 45 for all adults, with repeat colonoscopies every 10 years if results are normal.
Preparation Is Very Different
This is where the two procedures diverge most noticeably for patients. For an upper endoscopy, preparation is relatively simple: you fast for several hours beforehand, typically overnight, so your stomach is empty.
Colonoscopy prep is far more involved. Your colon needs to be completely clean for the doctor to see anything, which means drinking a bowel-preparation solution the day before and spending significant time in the bathroom. Most people describe the prep as the worst part of the entire experience. You’ll also need to follow a restricted diet in the days leading up to the procedure, avoiding high-fiber foods, seeds, and nuts before switching to clear liquids only.
What to Expect During the Procedure
Both procedures use sedation. Most patients receive moderate sedation, which keeps you relaxed and drowsy but still able to respond to verbal cues. Some cases call for deeper sedation, where you’re essentially asleep but still breathing on your own. Full general anesthesia with intubation is rare and reserved for complex cases or patients with specific medical needs. A large German study found the overall rate of sedation-related complications was 0.3%, with serious events occurring in just 0.01% of cases.
Upper endoscopies are generally quicker, often finishing in 15 to 20 minutes. Colonoscopies typically take 30 to 60 minutes depending on whether polyps need to be removed.
Recovery and Side Effects
After an upper endoscopy, the most common complaint is a mild sore throat that resolves within a day or two. You can usually eat again within a few hours once the sedation wears off.
After a colonoscopy, bloating and mild stomach cramps are normal. These come from the air that was pumped into your bowel during the exam, and they typically settle within 24 hours. A small amount of rectal bleeding is also normal, especially if polyps were removed or biopsies were taken. If you received sedation, plan to rest at home for the remainder of the day. Most people resume normal activities within 24 hours.
Safety of Both Procedures
Both upper endoscopy and colonoscopy are considered very safe. For diagnostic upper endoscopy, perforation (a small tear) occurs in roughly 1 in 2,500 to 1 in 11,000 procedures. Clinically significant bleeding after a diagnostic upper endoscopy is exceedingly rare, even when multiple biopsies are taken. Cardiopulmonary events, like a brief drop in oxygen levels, occur in up to 0.6% of upper endoscopies.
Colonoscopy carries similar low risks. The chance of perforation or significant bleeding is slightly higher when polyps are removed compared to a purely diagnostic exam, but these complications remain uncommon. In both procedures, temporary bacteremia (bacteria briefly entering the bloodstream) can occur in a small percentage of patients but rarely causes problems.
Can You Have Both at Once?
Yes. When a doctor needs to evaluate both the upper and lower GI tract, they can perform an upper endoscopy and colonoscopy during the same session while you’re under a single round of sedation. This is sometimes called a “bidirectional endoscopy.” It saves you from going through preparation and sedation twice, and doctors often combine the procedures when symptoms could originate from either part of the digestive tract.