Diverticulitis: Signs, Causes, and What Actually Helps

It usually starts as a dull ache on the lower left side of your belly, the kind you might blame on something you ate. Then it sharpens. A low fever creeps in. The pain does not fade after a bathroom trip or a night's sleep, and within a day or two you are in urgent care hearing a word you may never have heard before: diverticulitis.

It is one of the most common reasons American adults end up in the hospital with abdominal pain, yet most people know almost nothing about it until it strikes them. Roughly half of Americans over 60 have the underlying condition that sets the stage for it, and most of them never have a single symptom.

What diverticulitis actually is

Your colon is a muscular tube, and like any tube under pressure, it can develop weak spots. Over years, small pouches called diverticula can bulge outward through weak points in the colon wall, most often in the sigmoid colon, the S-shaped section on the lower left side of your abdomen. Having these pouches is called diverticulosis. About 1 in 3 Americans over 50 has it, and the share rises to roughly 1 in 2 by age 60.

Diverticulitis is what happens when one or more of those pouches becomes inflamed or infected. Most flares are mild and resolve with treatment. A minority become complicated, meaning the pouch tears, forms an abscess, or leaks into the abdominal cavity, and those cases need hospital care and sometimes surgery.

The symptoms that should make you pay attention

A diverticulitis flare usually announces itself clearly. The classic picture includes:

• Pain in the lower left abdomen that is persistent and tender to the touch, often lasting days rather than hours. It may start mild and build.
• Fever, usually low-grade at first, sometimes with chills.
• Nausea, loss of appetite, or vomiting.
• A change in bowel habits: constipation is most common, but some people get diarrhea.
• Bloating and abdominal tenderness, especially when you press on the left side.

Get urgent care promptly, the same day, if you have severe or worsening abdominal pain, a fever above 101 degrees Fahrenheit, vomiting that keeps you from keeping fluids down, or blood in your stool. Go to the emergency room for sudden severe pain, a rigid or swollen abdomen, fainting, or signs of shock such as a racing heart and cold, clammy skin.

What causes a flare?

Diverticula were once blamed simply on a low-fiber diet raising pressure inside the colon. That is part of the story, but not the whole one:

• Age and colon wall changes. The colon wall naturally weakens and loses elasticity with age, which is why diverticulosis is rare before 40 and common after 60.
• Low fiber intake. A diet low in fiber produces smaller, harder stools that require more pressure to move through the colon, encouraging pouches to form.
• Obesity and inactivity. Carrying extra weight, especially around the waist, and getting little physical activity are both linked to higher flare risk.
• Smoking. Smokers face a higher risk of complications from diverticulitis.
• Certain medications. Regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, as well as steroids and opioids, has been linked to higher flare risk.
• Genetics. Diverticular disease runs in families to a degree.

One thing that does not cause flares, despite decades of warnings: eating nuts, seeds, popcorn, and corn. Generations of patients were told to avoid them for fear a seed would lodge in a pouch. Large studies have found no such link, and the advice has been formally dropped.

How doctors diagnose it

Because diverticulitis shares symptoms with appendicitis, irritable bowel syndrome, inflammatory bowel disease, and even ovarian problems, doctors rarely rely on symptoms alone. A CT scan of the abdomen and pelvis with contrast is the standard test: it confirms the inflamed pouches, shows whether there is an abscess or perforation, and rules out other causes.

A colonoscopy is not done during an acute flare, because inflating the colon while it is inflamed risks tearing it. Once the flare has settled, usually six to eight weeks later, your doctor may recommend one to confirm the diagnosis and check for anything else hiding behind the inflammation.

Treatment: most flares do not need surgery

Most cases are uncomplicated and manageable without a hospital stay.

For a mild, uncomplicated flare, treatment is usually at home: rest, a clear-liquid diet for a day or two until the pain eases, then a gradual return to soft, low-fiber foods before working back up to normal eating. Pain relief typically comes from acetaminophen; NSAIDs are often avoided because they can irritate the gut. Your doctor will tell you whether antibiotics are needed. Notably, recent clinical guidance has moved away from automatic antibiotics for every uncomplicated case, since studies show many mild flares resolve without them.

Hospital treatment is needed when there is an abscess, perforation, severe pain, high fever, vomiting that prevents drinking, or an immune system weakened by medication or illness. In the hospital, treatment means IV antibiotics and IV fluids, bowel rest, and drainage of any abscess. Surgery is reserved for complications: a ruptured pouch, an abscess that cannot be drained, a blockage, or a fistula, an abnormal connection between the colon and another organ. Emergency surgery may involve removing the damaged section of colon, sometimes with a temporary colostomy bag that is usually reversed later.

Preventing the next flare

You cannot reverse diverticula once they exist, but you can substantially lower the odds they ever inflame again:

• Eat more fiber, gradually. Aim for roughly 25 grams a day for women and 38 grams for men, from foods like beans, lentils, whole grains, vegetables, and fruit. Add fiber slowly over a few weeks, with plenty of water, to avoid gas and bloating. During an active flare, fiber is temporarily reduced; the high-fiber goal applies once you have recovered.
• Move every day. Even brisk walking 30 minutes most days is associated with lower flare risk.
• Maintain a healthy weight. Losing even modest weight if you are overweight lowers inflammation overall.
• Do not smoke. Quitting lowers the risk of complications.
• Use NSAIDs sparingly. If you take ibuprofen or naproxen regularly, ask your doctor about alternatives, especially if you have already had a flare.
• Stay hydrated. Water keeps stools soft and moving, which is the whole point of the fiber strategy.

The bottom line

Diverticulitis is common, painful, and usually treatable, but it is not something to tough out at home. Persistent lower-left abdominal pain with fever deserves a same-day call to your doctor, and severe pain, vomiting, or blood in your stool deserves urgent care. Most flares settle with rest, diet changes, and, when needed, antibiotics. And the long game is refreshingly boring: more fiber, regular movement, a healthy weight, and no smoking.

This article is for general information only and is not medical advice. If you have abdominal pain, fever, or blood in your stool, contact your doctor or seek urgent care.