Most endoscopies come back completely normal or show minor, treatable conditions. In a large analysis of over 270,000 upper endoscopies, 41.5% were entirely normal. When something is found, it’s usually related to acid reflux, and in colonoscopies, polyps and small pouches called diverticula top the list. Here’s what doctors actually see when they look inside.
Upper Endoscopy: Reflux Dominates
An upper endoscopy (sometimes called an EGD) lets a doctor examine your esophagus, stomach, and the first part of your small intestine. The vast majority of abnormal findings are connected to gastroesophageal reflux disease, or GERD. Data from the NIDDK covering over 270,000 procedures breaks down the findings clearly:
- Mucosal abnormality: 38.8% of all procedures. This means the lining looks irritated, red, or irregular, often from stomach acid washing up into the esophagus or irritating the stomach itself.
- Hiatal hernia: 33.4%. A portion of the stomach pushes up through the diaphragm into the chest cavity. This is extremely common and, on its own, often causes no symptoms at all.
- Esophageal inflammation: 17.8%. Visible redness and swelling in the esophagus, typically from chronic acid exposure.
- Stricture or narrowing: 9.9%. Scar tissue from repeated acid damage can narrow the esophagus, making swallowing difficult.
- Barrett’s esophagus: 6.7%. The cells lining the lower esophagus change in response to years of acid exposure. This is monitored because it slightly raises the risk of esophageal cancer. Among people with chronic reflux symptoms, about 7% have Barrett’s. Even people without reflux symptoms can have it, at a rate of about 2.2%.
- Ulcers: 6.3%. Open sores in the stomach or upper intestine, caused by acid, certain medications (like ibuprofen or aspirin), or bacterial infection.
- Polyps: 4.5%. Small growths on the lining, usually benign.
When you add these up, the picture is clear: the overwhelming majority of abnormal findings on upper endoscopy trace back to acid reflux and its consequences.
Gastritis and H. Pylori Infection
Gastritis, a general term for inflammation of the stomach lining, is one of the most common reasons people get scoped in the first place. During the procedure, the doctor looks for diffuse redness, swelling, sticky mucus, and small bumps (nodularity), particularly in the lower portion of the stomach. These visual clues can suggest an active infection with H. pylori, a bacterium that burrows into the stomach lining and triggers chronic inflammation.
In endoscopy studies, roughly 18% of patients tested positive for active H. pylori infection. This number varies widely by region and population, but the infection remains a leading cause of stomach ulcers worldwide. If H. pylori is suspected, the doctor typically takes a small tissue sample during the procedure to confirm the diagnosis. Treatment involves a combination of antibiotics and acid-suppressing medication, and most people clear the infection successfully.
Ulcers: Less Common Than You’d Think
Peptic ulcers, the open sores that form in the stomach or duodenum, are found less often than many people expect. In a cross-sectional study of nearly 1.3 million patients who had upper endoscopies between 2009 and 2018, about 48,000 had gastric ulcers and 12,000 had duodenal ulcers. Only 17% of those ulcers tested positive for H. pylori, a proportion that has been declining over recent decades. The rest are largely attributed to long-term use of anti-inflammatory painkillers or other factors.
Colonoscopy: Polyps Are the Main Event
For lower endoscopy (colonoscopy), the single most important finding is polyps. These are small growths on the colon wall, and they’re detected in 30% to 50% of adults, depending on age, sex, and screening history. Most polyps are harmless, but a specific type called adenomas are precancerous. About two-thirds of precancerous polyps are adenomas, which can slowly develop into colon cancer if left in place. That’s exactly why they’re removed during the procedure.
Current quality benchmarks from the American Society for Gastrointestinal Endoscopy set the minimum adenoma detection rate at 35% overall, with targets of 40% for men and 30% for women. In practical terms, this means a competent doctor performing screening colonoscopies should find at least one adenoma in roughly one out of every three patients. If your colonoscopy report mentions an adenoma was removed, that’s the system working as intended.
Diverticulosis: Increasingly Common With Age
Diverticula are small pouches that form in the colon wall, and they’re among the most frequent incidental findings during colonoscopy. They rarely cause problems on their own, but their prevalence climbs sharply with age. In a U.S. screening population, 35% of patients aged 50 or younger had diverticula, 40% of those aged 51 to 60, and 58% of those over 60. The number of pouches also increases: 30% of people over 60 had more than 10 diverticula, compared to just 8% of those 50 and younger.
Most people with diverticulosis never develop symptoms. A small percentage go on to develop diverticulitis, where one or more pouches become inflamed or infected, but finding diverticula on a colonoscopy is generally not a cause for concern.
Hemorrhoids and Other Rectal Findings
Internal hemorrhoids show up in about 16% of screening colonoscopies. They’re dilated blood vessels in the anal canal, typically spotted as the scope is being withdrawn. For many people, this is the first time they learn they have them. Finding hemorrhoids during a colonoscopy is useful mainly because it can explain rectal bleeding and rule out more serious causes.
Areas of redness, swelling, or sores in the colon may indicate inflammation from infection, inflammatory bowel disease, or other causes. The location and pattern of inflammation help the doctor narrow down what’s going on, and biopsies are often taken from these areas for a closer look under a microscope.
Less Common but Notable Findings
Some findings are rarer but carry more clinical weight. Tumors are found in fewer than 1% of upper endoscopies. Varices, which are swollen veins in the esophagus or stomach caused by liver disease, appear in about 2.8% of upper endoscopy cases. Retained food or foreign bodies account for about 2.1%.
Celiac disease occasionally shows up as an unexpected finding. Endoscopic markers like scalloped folds and a mosaic pattern in the small intestine lining are visible in about 5% of patients undergoing routine upper endoscopy, though the condition itself can be present even when the lining looks normal. In one study of 150 patients scoped for general upper GI symptoms, 1 in 19 had villous atrophy, the hallmark tissue damage of celiac disease.
When ultrasound is added to upper endoscopy (a specialized technique called endoscopic ultrasound), incidental findings pop up in about 7% of cases. The most frequent surprise is gallstones that weren’t causing symptoms, accounting for roughly 40% of those incidental findings. Most of these are never treated, since only about 20% of people with silent gallstones go on to develop problems.
What a Normal Result Actually Means
If your endoscopy comes back normal, that’s genuinely reassuring. With over 40% of upper endoscopies showing no abnormality at all, a clean result is the single most common outcome. It doesn’t mean your symptoms aren’t real, but it does rule out structural problems, ulcers, and visible inflammation. Your doctor may pursue other explanations, like functional conditions that affect how the gut moves and processes signals rather than how it looks.
For colonoscopy, a clean result with no polyps typically means you won’t need another one for 10 years if you’re at average risk. If adenomas were found and removed, the recommended follow-up interval shortens to 3 to 5 years depending on the number, size, and type of polyps. Your pathology report, which comes back a week or two after the procedure, is the document that determines your next steps.