A gastroscopy looks for problems in your esophagus, stomach, and the first part of your small intestine. The most common findings are signs of acid reflux, including inflammation of the esophageal lining, hiatal hernias, and changes to the tissue that lines these organs. But the procedure can also detect ulcers, infections, pre-cancerous changes, celiac disease, swollen veins, and cancer.
Acid Reflux and Esophageal Damage
The single most common reason gastroscopies turn up abnormal results is gastroesophageal reflux disease (GERD). In a large analysis of over 270,000 procedures, esophageal inflammation appeared in nearly 18% of cases. During the exam, the doctor can see redness, swelling, or erosions where stomach acid has repeatedly damaged the lining of the esophagus. They can also spot a hiatal hernia, where the upper portion of the stomach pushes up through the diaphragm into the chest. This is one of the most frequently identified structural findings and often contributes to reflux symptoms.
If reflux has been going on for years, the esophageal lining can start to change. The normal tissue gets replaced by a different type of cell in a condition called Barrett’s esophagus. This matters because Barrett’s is considered pre-cancerous. Doctors measure the extent of these tissue changes in centimeters, noting how far the abnormal lining extends around and up the esophagus. If Barrett’s is found, biopsies are taken to check for early cellular changes that could eventually lead to esophageal cancer. Narrowing of the esophagus (strictures) from long-standing reflux is another finding the scope can identify.
Stomach and Duodenal Ulcers
Ulcers show up in about 6% of gastroscopies. These are open sores in the lining of the stomach or the duodenum, which is the first section of the small intestine. During the procedure, the doctor evaluates the ulcer’s size, shape, and edges to help distinguish a harmless peptic ulcer from something more concerning.
A typical benign ulcer has smooth, regular edges with surrounding tissue that looks swollen but symmetrical. Folds in the stomach lining radiate evenly toward the base of the ulcer. Most are less than 1 centimeter across and have a whitish or grayish base. A malignant ulcer looks different: the edges tend to be irregular, the surrounding folds are asymmetrical and may appear lumpy or clubbed, and there is often a visible mass around the ulcer. The tissue also behaves differently when biopsied. Benign ulcer tissue is firm with some flexibility and bleeds little, while cancerous tissue is stiff, crumbles easily, and bleeds more readily.
Helicobacter Pylori Infection
One of the key things a gastroscopy can do that imaging tests cannot is take tissue samples. A small piece of the stomach lining can be tested on the spot for H. pylori, the bacterium responsible for most stomach ulcers and a known risk factor for stomach cancer. The rapid urease test works by placing the tissue sample into a gel containing urea and a color indicator. H. pylori produces an enzyme that breaks down urea into ammonia, which raises the pH and triggers a color change from brown to pink, typically within minutes to hours.
For the most reliable results, two samples are usually taken: one from the lower part of the stomach (the antrum) and one from the main body of the stomach, avoiding areas that are already ulcerated or visibly abnormal. The same tissue sample can also be sent for additional testing, including checks for antibiotic resistance, which helps guide treatment if the infection is confirmed.
Pre-cancerous Changes and Cancer Screening
Tumors are found in fewer than 1% of gastroscopies, but part of the procedure’s value lies in catching problems before they become cancerous. When screening for pre-cancerous changes in the stomach, doctors follow a systematic biopsy approach. A standard protocol involves taking samples from multiple locations: the lesser and greater curves of the antrum, the lesser and greater curves of the stomach body, and a spot called the incisura angularis, which is a bend along the lesser curve where early changes tend to appear. Research suggests that even a streamlined approach using three well-placed biopsies (the lesser curve of the antrum, the lesser curve of the body, and the angularis) can accurately identify patients at higher risk for stomach cancer.
Barrett’s esophagus, mentioned earlier, is the main pre-cancerous condition found in the esophagus. If it is identified, periodic follow-up gastroscopies are typically recommended to watch for progression.
Celiac Disease
Gastroscopy is one of the primary tools for confirming celiac disease. The doctor examines the duodenum for visual clues that the immune reaction to gluten has damaged the intestinal lining. The two most recognizable signs are scalloping of the duodenal folds, which appears in about 57% of cases with confirmed tissue damage, and a mosaic pattern on the surface of the mucosa, seen in roughly 53%. These changes reflect villous atrophy, where the tiny finger-like projections that absorb nutrients have been flattened or destroyed.
However, these visual markers are not always present, so biopsies of the duodenal lining are taken even when the tissue looks relatively normal if celiac disease is suspected. The tissue samples are examined under a microscope to confirm whether damage has occurred at a level too subtle to see with the camera alone.
Esophageal Varices
In people with liver disease, gastroscopy looks for varices, which are swollen veins in the esophagus or stomach. These develop when scarring in the liver forces blood to find alternative routes, causing veins in the esophageal wall to balloon outward. Varices are dangerous because they can rupture and cause life-threatening bleeding.
Doctors grade varices by size: mild (under 3 mm), moderate (3 to 6 mm), and severe (over 6 mm). They also look for “red signs” on the surface of the veins, including red streaks and cherry-red spots, which indicate a higher risk of bleeding. Large varices that resemble the mucosal folds of the esophagus itself represent the most advanced stage. The grading determines how urgently treatment is needed and whether preventive measures should be started.
What Happens During and After the Procedure
The procedure itself typically takes 10 to 15 minutes. You can choose to have it done with just a numbing throat spray, or you can receive sedation. In the UK, most sedated procedures use a short-acting sedative from the benzodiazepine family, sometimes combined with a painkiller. An inhaled mixture of nitrous oxide and oxygen is another option that wears off quickly and allows discharge within 30 minutes of the procedure.
Recovery depends on whether you were sedated. If you had only a throat spray, you can generally leave once the numbness wears off. If you received sedation, you will need to stay in the recovery area until you are fully awake and your protective reflexes have returned. After that, staff will go over initial findings and discharge instructions. You should not drive, operate machinery, sign legal documents, or drink alcohol for 24 hours after sedation. With nitrous oxide, these restrictions do not apply.
Biopsy results, if samples were taken, usually come back within a few days to two weeks. The rapid urease test for H. pylori can give a preliminary answer the same day, but tissue sent for microscopic analysis takes longer. Your doctor will typically schedule a follow-up to discuss biopsy findings and any next steps.