Diverticulitis: symptoms, causes and when to get help

In short

• Diverticulitis means that one or more pouches (diverticula) in the colon wall have become inflamed. The classic picture is pain in the lower left belly with fever, chills, nausea and a change in bowel habits.
• The pouches themselves, called diverticulosis, are common with age and usually cause no symptoms at all.
• Uncomplicated diverticulitis is often managed at home. Severe illness, complications or a high risk of complications usually mean hospital care, and antibiotics are common but not needed by everyone.
• Get emergency help for severe belly pain with vomiting, a swollen belly, being unable to pass stool or gas, heavy bleeding from the bottom, or confusion and fast breathing.
• After recovery, a fiber-rich diet, regular activity, a healthy weight and not smoking may lower the risk of another attack.

What diverticulitis is and how common it is

Diverticula are small pouches that push outward through weak spots in the colon wall, mostly in the sigmoid colon, the lower left part of the large intestine. Having them is called diverticulosis. When the pouches cause bleeding, inflammation or other trouble, the condition is called diverticular disease, and inflamed pouches are diverticulitis.

Pouches become more likely with age. More than 30% of U.S. adults aged 50 to 59 have them, and more than 70% of adults older than 80. Most people never notice. NIDDK, the U.S. digestive disease research institute, reports that about 200,000 people in the country are hospitalized for diverticulitis each year.

Under age 50, diverticulitis is more common in men. From 50 on, it is more common in women.

Symptoms: what is typical and what is not

• Pain in the lower left belly, usually severe and sudden, though it can also start mild and build over several days. Its strength may change over time.
• Fever and chills.
• Nausea or vomiting.
• Constipation or diarrhea.
• In the UK, the NHS adds blood or mucus from the bottom and a high temperature. A few people feel the pain on the right side instead.

Many people with pouches have milder, longer-lasting complaints such as bloating, cramping in the lower belly, constipation or diarrhea. Irritable bowel syndrome can cause the same symptoms, so these complaints alone do not prove diverticular disease. Some people first learn they have it when a complication develops.

Causes and risk factors

Experts do not know the exact cause. Genes may make some people more likely to develop the disease, and researchers are looking at stool or bacteria trapped in a pouch, changes in gut bacteria, problems with the nerves, muscles and connective tissue of the colon, and immune system problems.

• A diet low in fiber and high in red meat.
• Little physical activity.
• Obesity.
• Smoking.
• Some medicines, including NSAIDs (anti-inflammatory painkillers such as ibuprofen) and steroids.
• Older age.

What to do when you think you have it

1. Call.If you have lower belly pain with fever, contact your primary care provider the same day. Do not wait to see whether it fades, particularly if this is your first attack.
2. Rest the gut.If your provider agrees, a short clear liquid diet is used to rest the colon. Solid food is then added back slowly as symptoms improve.
3. Choose pain relief carefully.Ask which painkiller is right for you. NIDDK says antispasmodics or acetaminophen are preferred over NSAIDs, which may raise the chance of complications. The NHS also advises against opioid painkillers such as codeine.
4. Take medicines as prescribed.If you receive antibiotics, follow your provider's instructions and do not change the plan on your own.
5. Watch for change.Pain that gets worse, a rising fever, vomiting or bleeding means you should be seen again, or go to the emergency room.

When to see a doctor

• Lower belly pain that is new, persistent or getting worse.
• Fever or shivering with belly pain.
• Blood or mucus in your stool.
• You cannot keep fluids down, or diarrhea lasts more than 7 days or vomiting more than 2 days (NHS advice).
• Bloating, constipation, diarrhea or lower belly pain that keeps returning.

Red flags, call 911 now: severe belly pain together with vomiting; a swollen, hard belly; being unable to pass stool or gas; heavy bleeding from the rectum; confusion, pale or blotchy skin, abnormal temperature or fast breathing, which can be signs of sepsis. These can point to perforation, peritonitis, obstruction or severe bleeding.

How a doctor confirms it

A provider takes your history, examines your belly and may order tests. Blood tests look for signs of diverticulitis or its complications. A stool test helps separate diverticular disease from problems such as irritable bowel syndrome. Imaging, most often a CT scan, can show the inflamed colon; ultrasound and MRI are other options.

A colonoscopy uses a flexible tube with a camera to view the colon. Doctors order it when needed, to confirm the diagnosis, to rule out other conditions such as cancer, or to find and treat bleeding from a pouch. Your doctor decides if and when you need one.

Treatment in general terms

• Care setting. Uncomplicated cases may be treated at home. Severe cases, complications or a high risk of complications usually call for a hospital stay.
• Antibiotics. Often used, but not for everyone.
• Diet. A brief clear liquid diet, then slowly returning to solid food.
• Pain relief. Antispasmodics or acetaminophen are preferred over NSAIDs.
• Abscess. A small abscess may be treated with antibiotics; a large one that does not respond may be drained.
• Surgery. Removal of part of the colon may be needed if the illness does not improve or leads to complications such as a fistula, blockage, perforation or peritonitis.

Rectal bleeding is treated as an urgent matter. Depending on the cause, the team may use colonoscopy to stop it, an angiogram, surgery or blood transfusion. All of these decisions belong to your doctor.

Lowering the chance of another attack

• Eat more fiber and less red meat. The Dietary Guidelines suggest 28 grams of fiber a day on a 2,000-calorie diet, and your provider may ask you to increase it gradually.
• Stay physically active and aim for a healthy weight.
• Do not smoke.
• Review your medicines with your doctor, since some raise the risk.
• After an uncomplicated attack, surgery to remove part of the colon may be considered to prevent recurrence, depending on your history and health.

Good sources of fiber include lentils, beans, chickpeas, peas, broccoli, sweet potato, apples with skin, raspberries, prunes and whole-grain cereal. Add them step by step so your body can adjust, and ask for help from a dietitian if you want a plan.

Questions and answers

Sources

1. NIDDK — Definition & Facts for Diverticular Disease
2. NIDDK — Symptoms & Causes of Diverticular Disease
3. NIDDK — Diagnosis of Diverticular Disease
4. NIDDK — Treatment of Diverticular Disease
5. NIDDK — Eating, Diet & Nutrition for Diverticular Disease
6. NHS — Diverticular disease and diverticulitis

Sources checked on 28 October 2026.