Active enteritis

by Jason Wasserman MD PhD FRCPC
June 13, 2025

Active enteritis refers to inflammation of the small intestine, involving specialized immune cells known as neutrophils. This finding suggests recent or ongoing irritation, infection, or injury to the intestinal lining. Pathologists identify active enteritis by examining tissue samples from your intestine under a microscope.

What are the symptoms of active enteritis?

Symptoms of active enteritis often appear suddenly and may include:

• Diarrhea, which may be watery or contain blood.

• Abdominal pain or cramping.

• Nausea or vomiting.

• Fever or chills, especially if caused by an infection.

• Reduced appetite or fatigue due to illness.

These symptoms can range from mild discomfort to more severe issues that affect daily life.

What causes active enteritis?

Active enteritis commonly results from recent or ongoing irritation or injury to the intestine. Causes include:

• Infections: Bacteria (such as Salmonella or Campylobacter), viruses (like norovirus), or parasites can trigger active inflammation.

• Medication reactions: Certain medications, especially non-steroidal anti-inflammatory drugs (NSAIDs), can irritate the intestinal lining.

• Inflammatory bowel disease (IBD): Conditions like Crohn’s disease or ulcerative colitis often cause active inflammation, particularly during flare-ups.

• Radiation therapy: Treatments involving radiation to the abdomen or pelvis may temporarily irritate the intestine, causing active enteritis.

• Reduced blood flow (ischemia): Decreased blood supply to the intestine can lead to injury and active inflammation.

Your doctor will evaluate your symptoms, medical history, and other test results to determine the most likely cause.

What is the difference between active and chronic enteritis?

Enteritis can be described as either active or chronic, based on the type of inflammatory cells seen under the microscope and the duration of symptoms:

• Active enteritis: Involves neutrophils (immune cells responding rapidly to recent injury or infection). It typically indicates recent irritation and may present with sudden symptoms, such as diarrhea and abdominal pain.

• Chronic enteritis: Involves lymphocytes and plasma cells (immune cells associated with long-lasting inflammation). Chronic enteritis usually indicates ongoing conditions like celiac disease or inflammatory bowel disease and may cause persistent symptoms like long-term diarrhea, nutrient deficiencies, and weight loss.

Sometimes, active and chronic inflammation can occur simultaneously, especially when ongoing irritation is combined with a recent injury or infection.

Why is identifying active enteritis important?

Recognizing active enteritis helps your doctor understand the underlying cause of your symptoms and choose appropriate treatment. Because active enteritis suggests recent or ongoing injury or infection, timely identification allows your doctor to provide prompt treatment to relieve symptoms, prevent complications, and help your intestine heal properly.

Questions to ask your doctor

• What is causing my active enteritis?

• Will I need additional tests to determine the exact cause?

• What treatments are available based on this diagnosis?

• How long will it take for my symptoms to improve after treatment?

• Are there dietary or lifestyle changes that can help relieve my symptoms?

• Will I require ongoing follow-up appointments or tests?

• Are there any complications I should be aware of?

• Could this condition recur in the future, and if so, how can I prevent it?