Chronic Active Gastritis: Understanding Your Pathology Report

Section Editor: David Driman
November 10, 2026

Chronic active gastritis is a type of inflammation in the lining of the stomach. “Chronic” means the inflammation has been present for a long time, usually months or years. “Active” means immune cells called neutrophils are present and causing ongoing injury to the lining.

Chronic active gastritis is not cancer, and in most people it is caused by infection with a bacterium called Helicobacter pylori (H. pylori), which can usually be cured with medicines. This article explains what chronic active gastritis means, how the diagnosis is made, and what the other findings in your pathology report mean.

What causes chronic active gastritis?

In most cases, H. pylori infection causes chronic active gastritis. If the pathologist sees the bacteria in the biopsy, the diagnosis may be written as Helicobacter gastritis. In other cases, the report describes chronic active gastritis and notes that no bacteria were seen. When no bacteria are found, possible explanations include:

Hidden H. pylori infection. Acid-reducing medicines called proton pump inhibitors, recent antibiotics, and bismuth can reduce the number of bacteria, making them hard to detect. A breath or stool test done after stopping these medicines may still detect the infection.
Recent treatment. After H. pylori is cured, the inflammation in the stomach lining takes time to settle. Neutrophils usually disappear within a few months, while the chronic inflammation fades more slowly over a longer period.
Other Helicobacter species. Rarely, related bacteria such as Helicobacter heilmannii infect the stomach, and these bacteria are larger than H. pylori and usually cause milder inflammation.
Crohn disease. People with Crohn disease can have small, patchy areas of active inflammation in the stomach. This pattern is sometimes called focally enhanced gastritis.

Some medicines and substances, such as anti-inflammatory pain relievers, alcohol, and bile, also injure the stomach lining. However, they usually cause a different pattern with little inflammation, called reactive gastropathy or chemical gastropathy.

What are the symptoms of chronic active gastritis?

Many people with chronic active gastritis have no symptoms, and doctors find the inflammation on a biopsy taken for another reason. When symptoms do occur, they are often vague and can include:

Upper abdominal pain or burning. The pain is often felt in the upper middle part of the abdomen and may be worse when the stomach is empty.
Bloating, nausea, or loss of appetite. Some people feel full quickly, or feel bloated and uncomfortable after small meals.
Symptoms of an ulcer. Black, tarry stools, vomiting blood, or feeling faint can be signs of a bleeding ulcer and need urgent medical attention.

How is the diagnosis made?

A pathologist diagnoses chronic active gastritis by examining a tissue sample from the stomach under a microscope. The sample is usually taken as a small biopsy during an upper endoscopy, a procedure that uses a thin tube with a camera to view the inside of the stomach.

Under the microscope, the pathologist sees two types of inflammation in the mucosa, the stomach’s inner lining. The first type is chronic inflammation, made of lymphocytes and plasma cells. The second type is active inflammation, made of neutrophils, which often move into the surface cells and the small pits that open onto the stomach surface. When neutrophils are not seen, the report may say “chronic inactive gastritis” instead.

The pathologist also looks for H. pylori bacteria on the surface of the lining. When the bacteria are hard to see, the pathologist may use a special stain such as Giemsa or immunohistochemistry for H. pylori. Your report will usually state clearly whether bacteria were seen.

Grading the gastritis

Many pathologists grade chronic active gastritis using the updated Sydney System, which was published in 1996. This system rates each feature as absent, mild, moderate, or marked, based on how much of it is seen. The amount of activity is described as follows:

Mild activity. A few neutrophils are seen in the lining, with only occasional neutrophils among the surface cells.
Moderate activity. More neutrophils are present, and many have moved into the surface cells and the pits of the lining.
Marked activity. Large numbers of neutrophils are present, and they may collect inside the pits to form small pockets called pit abscesses.

The report may also grade the amount of chronic inflammation and the number of bacteria seen on the surface. Activity usually reflects how heavy the infection is, and it is often the first finding to improve after treatment. The report may also describe an erosion or an ulcer, where part of the lining has worn away.

Intestinal metaplasia, atrophy, and dysplasia

Intestinal metaplasia, atrophy, and dysplasia can develop after many years of chronic active gastritis. Your report will usually say whether each one is present:

Intestinal metaplasia. Part of the stomach lining is replaced by cells that look like the lining of the small intestine. This change is not cancer, but it raises the long-term risk of a stomach cancer called adenocarcinoma, especially when it is widespread.
Atrophy. The stomach’s normal glands are lost and replaced by scar tissue or other cell types. Extensive atrophy is described in our article on atrophic gastritis.
Dysplasia. A precancerous change in which the cells lining the stomach look abnormal under the microscope. Most reports for chronic active gastritis state that the biopsy is negative for dysplasia. If dysplasia is found, it is described as low-grade or high-grade, and closer follow-up or treatment is usually recommended.

What are the possible complications?

Most people with chronic active gastritis never develop a serious complication, especially when the cause is found and treated. When the cause is long-lasting H. pylori infection, possible complications include:

Stomach and duodenal ulcers. Open sores can form in the stomach lining or the first part of the small intestine. Curing the infection greatly reduces the chance of an ulcer returning.
Stomach adenocarcinoma. Many years of inflammation can lead to atrophy, intestinal metaplasia, dysplasia, and cancer in a small number of people. Treating the infection lowers this risk.
MALT lymphoma. A rare, usually slow-growing cancer of immune cells in the stomach lining that is strongly linked to long-lasting H. pylori infection.

What happens after the diagnosis?

Once chronic active gastritis has been confirmed, the next steps depend mainly on whether H. pylori was found in the biopsy or by another test. Your doctor may consider:

Treatment for H. pylori. When the bacteria are found by biopsy or by a breath or stool test, treatment combines an acid-reducing medicine with antibiotics for 14 days. Bismuth quadruple therapy is a recommended first choice in the Canadian (2016) and American (2024) guidelines. Our Helicobacter gastritis article describes the options in more detail.
A test of cure. A breath or stool test done at least four weeks after finishing treatment is recommended to confirm that the infection is gone.
More testing when no bacteria are seen. Your doctor may order a breath or stool test, review your medicines, or look for other causes such as Crohn disease.
Follow-up endoscopy. People with extensive intestinal metaplasia, atrophy, or dysplasia may be offered repeat endoscopy to watch the stomach lining over time.

Questions to ask your doctor

Were H. pylori bacteria seen in my biopsy?
Was a special stain or immunohistochemistry used to look for bacteria?
How active was the gastritis, and which parts of my stomach were affected?
If no bacteria were seen, what else could be causing the inflammation?
Should I have a breath or stool test, and do I need to stop any medicines first?
Did my biopsy show intestinal metaplasia, atrophy, or dysplasia?
Which treatment do you recommend, and when should I have a test of cure?
Should members of my household be tested for H. pylori?
Will I need a repeat endoscopy, and if so, when?