Enteritis

Enteritis means inflammation of the small intestine, the part of the digestive system between the stomach and large intestine. It absorbs nutrients and much of the water from food.

Infections are the most common cause of short-term enteritis. Viruses, bacteria, or parasites can irritate the intestine. Other causes include radiation treatment, certain medicines, reduced blood flow, Crohn’s disease, and coeliac disease.

Enteritis is related to gastroenteritis but is not exactly the same. Gastroenteritis involves the stomach and intestines and commonly causes vomiting as well as diarrhoea. Enteritis specifically refers to inflammation of the small intestine, although the terms may overlap in everyday use.

Many cases improve within several days with fluids and rest. However, diarrhoea and vomiting can cause dehydration, and some causes need specific treatment. Medical assessment is important when symptoms are severe, persistent, or linked to another health condition.

Symptoms may begin suddenly with an infection or develop gradually from another cause.

Common symptoms include:

• Loose or watery diarrhoea
• Abdominal cramps or pain
• Nausea or vomiting
• Reduced appetite
• Fever
• Tiredness
• Bloating or excess wind

Some people have mucus or blood in their bowel movements. Blood is not typical of a simple viral infection and should be medically assessed.

Signs of dehydration include a dry mouth, strong thirst, dark urine, passing less urine, dizziness, or unusual weakness. Babies, older adults, and people with certain long-term conditions can become dehydrated more quickly.

Long-lasting enteritis may interfere with nutrient absorption, leading to weight loss, vitamin or mineral deficiencies, weakness, or poor growth in children.

Viruses such as norovirus and rotavirus are frequent causes of acute enteritis. They can spread through contaminated food, water, surfaces, or close contact.

Bacterial enteritis may follow exposure to organisms such as Campylobacter, Salmonella, Shigella, or certain strains of Escherichia coli. Parasites, including Giardia, can cause longer-lasting illness and may be associated with contaminated water or travel.

Non-infectious causes include:

• Crohn’s disease
• Coeliac disease
• Radiation treatment involving the abdomen or pelvis
• Medicines that can injure the intestine, including some anti-inflammatory or cancer medicines
• Reduced blood flow to the intestine, called intestinal ischaemia
• Reactions after some types of abdominal surgery or cancer treatment

Risk is higher with unsafe food or water, poor sanitation, travel to areas where food- and waterborne infections are common, or close contact with someone who has diarrhoea.

A weakened immune system can increase the risk of severe or unusual infections. Very young children and older adults are also more vulnerable to complications from fluid loss.

A clinician may ask when symptoms began, how often you pass stool, and whether you have blood, fever, vomiting, recent travel, antibiotic use, or possible exposure to contaminated food. Your medicines and health conditions are also relevant.

An examination can check for dehydration, abdominal tenderness, fever, and signs of complications.

Testing is not always needed for a brief, mild episode. If symptoms are severe, bloody, persistent, or linked to travel or an outbreak, a stool sample may be tested for bacteria, viruses, parasites, or toxins.

Blood tests can identify dehydration, altered salt levels, anaemia, inflammation, or kidney problems. They may also help investigate coeliac disease or another underlying condition.

A CT scan may be needed for severe pain or a suspected complication. Endoscopy uses a flexible camera to examine the digestive tract. Tissue samples may be taken if Crohn’s disease, coeliac disease, chronic inflammation, or radiation injury is suspected.

Treatment depends on the cause and severity of fluid loss.

Replacing fluids is the main treatment for most short-term infectious cases. Oral rehydration solution contains water, salts, and sugar in proportions that help the intestine absorb fluid. Small, frequent drinks may be easier to tolerate than large amounts. Severe vomiting or dehydration may require fluids through a vein in hospital.

Food can usually be continued or restarted as tolerated. Small, simple meals may feel easier during active symptoms. Long periods without food are generally unnecessary, and breastfed babies can usually continue breastfeeding.

Antibiotics like amoxicillin or doxycycline do not treat viral enteritis. They are used only for selected bacterial infections when the likely benefit outweighs the risks. Certain bacterial illnesses can become worse with some antibiotics, so treatment should follow medical assessment.

Antiparasitic medicines may be prescribed when testing identifies a treatable parasite. Medicines that slow diarrhoea are not appropriate in every case, particularly when there is bloody stool, fever, or suspected invasive infection.

For non-infectious enteritis, treatment focuses on the underlying cause. This may involve treating Crohn’s or coeliac disease, adjusting a contributing medicine, or managing radiation effects. Nutrient absorption problems may require dietetic support or vitamin and mineral replacement.

Do not stop prescribed medicine or cancer treatment on your own because of bowel symptoms. Ask the treatment team whether it may be contributing and whether changes are appropriate.

Dehydration is the most common complication. Significant fluid loss can disturb sodium, potassium, and other body salts and may reduce kidney function.

Ongoing inflammation can impair absorption of calories, protein, vitamins, and minerals. Possible effects include weight loss, anaemia, weak bones, or delayed growth in children.

Less common complications include intestinal bleeding, a tear or hole in the bowel, scar-related narrowing, or infection spreading beyond the intestine. These are more likely with certain bacterial infections, reduced blood flow, radiation injury, or chronic inflammatory conditions.

Vomiting or diarrhoea can also affect medicines used for other conditions. People taking insulin, water tablets like furosemide or hydrochlorothiazide, or medicines affected by dehydration may need timely medical advice.

Not every type of enteritis can be prevented. Causes such as Crohn’s disease, coeliac disease, necessary radiation treatment, or unpredictable medicine reactions may occur despite appropriate care.

To reduce the risk of infectious enteritis:

• Wash hands with soap and water after using the toilet and before handling food
• Cook meat, poultry, seafood, and eggs thoroughly
• Keep raw foods separate from ready-to-eat foods
• Use safe drinking water, particularly during travel or outdoor activities
• Avoid preparing food for others while you have diarrhoea or vomiting
• Follow local guidance about returning to work, school, or childcare

Rotavirus vaccination helps protect infants and young children where it is part of the routine vaccination programme. It does not prevent every cause of enteritis.

Careful radiation planning and symptom monitoring can reduce the effects of radiation enteritis but cannot always prevent it.

Most infection-related enteritis is short-lived. Symptoms often settle as the immune system clears the infection and fluids are replaced, although appetite and bowel habits may take longer to return to normal.

Temporary food sensitivity can occur after an intestinal infection. The small intestine may briefly produce less lactase, the enzyme that digests milk sugar, causing bloating or loose stool after dairy products. This usually improves as the intestine heals, but persistent symptoms should be assessed.

Enteritis that lasts for weeks or repeatedly returns needs investigation. The outlook depends on the cause. A parasite may clear after targeted treatment, while coeliac-related inflammation can heal after diagnosis and removal of gluten from the diet. Crohn’s disease may alternate between active periods and remission.

Radiation enteritis can develop during treatment or months to years later. Some people have mild bowel changes, while others need longer-term medicines, nutrition support, or procedures.

For follow-up, keep track of bowel frequency, blood, fever, weight changes, recent foods, travel, and medicines. Arrange routine review if symptoms are improving but have not fully settled or if a chronic cause requires monitoring.

Arrange prompt medical advice if diarrhoea lasts more than a few days, keeps returning, or occurs with fever, weight loss, blood, or significant abdominal pain. Seek earlier assessment for babies, frail older adults, pregnant people, and anyone with a weakened immune system or serious long-term condition.

Seek urgent medical care if you cannot keep fluids down, pass very little urine, become increasingly dizzy, or have worsening signs of dehydration.

Get urgent or emergency help for:

• Severe, constant, or rapidly worsening abdominal pain
• A swollen or rigid abdomen
• A large amount of blood or black, tar-like stool
• Fainting, confusion, marked drowsiness, or difficulty waking
• Vomit containing blood or material that looks like coffee grounds
• Breathing difficulty or other signs of a severe allergic reaction

Mild symptoms that are steadily improving can often be monitored with fluids and rest. Persistent symptoms, even without emergency signs, should still be reviewed to identify the cause.

Is enteritis contagious?

The inflammation itself is not contagious, but viral, bacterial, and parasitic causes may spread between people or through contaminated food, water, or surfaces. Enteritis caused by radiation, medicines, coeliac disease, or Crohn’s disease is not contagious.

How long does enteritis last?

Many viral and mild foodborne cases improve within several days. Some bacterial or parasitic infections last longer. Enteritis caused by radiation or an ongoing inflammatory condition may continue or recur over months or years.

What can I eat with enteritis?

Eat what you can tolerate, using smaller meals if nausea or cramping makes larger meals difficult. Fluids are the priority. Very fatty foods, alcohol, and large meals may worsen symptoms. A restrictive diet is not usually needed unless a specific cause has been diagnosed.

Is enteritis the same as food poisoning?

Not always. Food poisoning can cause enteritis when food carries an infection or toxin. Enteritis can also result from contaminated water, person-to-person infection, medicines, radiation, or immune-related conditions.

Can enteritis go away without antibiotics?

Yes. Most viral cases and some mild bacterial cases resolve without antibiotics. Antibiotics help only with selected infections and can sometimes cause side effects or worsen particular bacterial illnesses.

Can enteritis become chronic?

Yes, although short-term infectious enteritis is more common. Chronic inflammation may be related to Crohn’s disease, coeliac disease, radiation injury, medicines, or an unresolved infection. Symptoms lasting for weeks or repeatedly returning need medical assessment.