Gastritis is inflammation of the stomach lining, and what it looks like depends on whether you’re talking about what a doctor sees during an endoscopy, what shows up on imaging, or what visible signs you might notice yourself. During an endoscopy, the most common appearance is a red, swollen stomach lining, sometimes with shallow breaks in the surface called erosions. From the outside, gastritis itself isn’t visible, but it can produce changes in vomit or stool that signal something is wrong.
What Gastritis Looks Like During an Endoscopy
An endoscopy is the most direct way to see gastritis. A thin, flexible camera is passed down your throat into your stomach, giving your doctor a live view of the lining. Healthy stomach tissue appears smooth and pink with visible folds. Inflamed tissue looks distinctly different.
In non-erosive gastritis, the lining appears red and swollen. The redness can be patchy or spread across a wide area. The mucosa (the inner surface layer) may look puffy or have a bumpy, cobblestone-like texture called nodularity. In some cases, a sticky, pale yellow-to-white mucus clings to the surface and can’t be easily washed away with water. This sticky mucus shows up in roughly a third of autoimmune gastritis cases.
Erosive gastritis looks more severe. The lining has visible shallow breaks, like small scrapes or raw spots, and in more serious cases, actual ulcers. Acute erosive gastritis can develop these erosions quickly, sometimes with active bleeding visible during the procedure. The tissue around erosions often appears especially red and fragile.
How Different Types Look Different
Not all gastritis looks the same through the scope. The visual pattern often points to the underlying cause.
When Helicobacter pylori bacteria are responsible, the most recognizable features include diffuse redness across the stomach lining, nodularity (a bumpy, “goose-flesh” texture), enlarged folds, and yellowish flat patches called xanthomas. A distinctive pattern called “map-like redness,” irregular red patches with clear borders, is also associated with active H. pylori infection. Nodularity and diffuse redness have especially high diagnostic accuracy for identifying an active infection.
Autoimmune gastritis has a very different appearance. Because the immune system attacks the acid-producing glands concentrated in the upper stomach (the body and fundus), those areas show the most damage while the lower stomach (the antrum) looks relatively normal. This reversed pattern is a hallmark. Over time, the lining in the affected area becomes visibly pale and thin, blood vessels underneath become more visible through the thinned tissue, and the normal stomach folds flatten out. Multiple small polyps may develop in the upper stomach. About one in five people with autoimmune gastritis develops these growths.
What Advanced Gastritis Looks Like
When gastritis persists for months or years without treatment, the stomach lining can undergo more dramatic changes. The normal glandular tissue gets replaced, a process called atrophy. According to the American Gastroenterological Association, atrophic gastritis has a characteristic pale appearance, with increased visibility of the blood vessels underneath due to thinning of the mucosa and loss of the stomach’s natural folds.
In more advanced stages, the stomach lining can develop intestinal metaplasia, where stomach cells are gradually replaced by cells that resemble intestinal tissue. Under specialized light during endoscopy, this shows up as light blue crests and white opaque fields on the surface. These changes are important because they represent a progression that doctors monitor closely over time.
What Shows Up on a CT Scan
Gastritis doesn’t always require an endoscopy to detect. It sometimes appears on CT scans done for other reasons, though the findings are less specific. The primary sign on CT is thickening of the stomach wall. Normal stomach wall thickness is relatively thin, but in H. pylori gastritis, the wall of the lower stomach (the antrum) often thickens to 1.5 to 2.0 centimeters. Wall thickening beyond 12 millimeters in the antrum is generally considered abnormal.
The limitation of CT is that wall thickening alone doesn’t confirm gastritis. Thickening can also indicate other conditions, so CT findings typically lead to further investigation with endoscopy rather than serving as a final diagnosis.
Signs You Can See Yourself
Most people with gastritis don’t see anything unusual. The condition often causes no visible external signs at all. When symptoms are present, they’re felt rather than seen: pain or discomfort in the upper abdomen, nausea, feeling full too soon during a meal, or feeling uncomfortably full afterward.
The exception is when erosive gastritis causes bleeding. If that happens, there are two visible warning signs. The first is in vomit: fresh red blood suggests active bleeding in the stomach, while dark brown material with a texture resembling coffee grounds indicates older blood where the bleeding has slowed or stopped. The second is in stool: blood from the stomach gets digested as it passes through the intestines, producing jet-black, tarry, sticky stools with a distinctly strong odor. This is called melena, and it looks completely different from the bright red blood you’d see with bleeding from the lower digestive tract.
What a Biopsy Reveals Under the Microscope
During endoscopy, doctors often take small tissue samples to examine under a microscope. This level of detail is invisible to the naked eye but tells a more precise story about what’s happening in the tissue.
In H. pylori gastritis, the biopsy shows clusters of immune cells (particularly plasma cells) concentrated near the surface, with deeper pockets of immune tissue and white blood cells infiltrating the lining of the stomach’s tiny glands. The bacteria themselves may be visible clinging to the surface layer.
Autoimmune gastritis looks different at the cellular level. The damage is concentrated deeper in the tissue, where the acid-producing glands sit. These glands are progressively destroyed and replaced by mucus-producing cells or cells that look like intestinal tissue. There’s also an overgrowth of certain hormone-producing cells that normally help regulate acid production, a response to the loss of acid-making capacity.
A less common pattern, called mid-and-deep-zone gastritis, shows inflammation concentrated in the middle and lower layers of the stomach lining rather than at the surface. In these cases, the acid-producing cells show visible injury and loss, and the regenerative zone of the tissue expands as the stomach tries to repair itself. Unlike autoimmune gastritis, this type doesn’t produce the same intestinal-type cell replacement in the stomach body.
How Doctors Grade What They See
Gastritis isn’t simply “present” or “absent.” Doctors use a standardized system called the Updated Sydney System to grade what they find. This framework combines three layers of information: where in the stomach the gastritis appears, what the tissue changes look like, and what’s causing them. Using visual reference scales, pathologists rate features like the degree of inflammation, the amount of glandular loss, and the presence of intestinal-type cell changes on a spectrum from mild to severe. The system draws a clear distinction between atrophic gastritis (where gland tissue has been lost) and non-atrophic gastritis (where inflammation is present but the glands are still intact), since these categories carry different implications for long-term monitoring.