Diverticulosis is the presence of small pouches in your colon wall. Diverticulitis is what happens when one or more of those pouches becomes inflamed or infected. Most people with diverticulosis never develop diverticulitis, and the two conditions feel very different in daily life.
How the Pouches Form
Your colon wall has layers of muscle with small gaps where blood vessels pass through. Over time, the inner lining of the colon can bulge outward through these weak spots, forming small pockets called diverticula. This is diverticulosis, and it’s one of the most common findings on routine colonoscopy, especially in people over 50. Having these pouches is not a disease. It’s a structural change that, for most people, causes no problems at all.
Diverticulitis occurs when small tears develop in one or more of these pouches, triggering inflammation or infection. The surrounding fat and tissue usually wall off the problem, keeping it contained. But in more severe cases, the tear can lead to an abscess, a connection between the colon and a nearby organ (called a fistula), or rarely, a rupture that spills intestinal contents into the abdominal cavity.
How Common Is the Progression
Only about 4% of people with diverticulosis ever develop diverticulitis. That number is much lower than older estimates suggested, and it means the vast majority of people with pouches in their colon will live their entire lives without an episode of inflammation. The shift in understanding matters because it means having diverticulosis on a colonoscopy report is not a reason to worry about inevitable future problems.
Symptoms of Each Condition
Diverticulosis typically causes no symptoms. Some people notice mild cramps, bloating, or constipation, but these overlap with so many other digestive issues that diverticulosis is rarely identified from symptoms alone. It’s almost always found incidentally during a colonoscopy or imaging scan done for another reason.
Diverticulitis announces itself more clearly. The hallmark symptoms are steady abdominal pain and tenderness to pressure in the lower abdomen, particularly on the left side. Beyond that, you may experience:
- Fever and chills
- Nausea or vomiting
- A change in bowel habits, either constipation or diarrhea
- Sharper pain with breathing, walking, or other jarring movements
The pain pattern is a useful distinguishing feature. Diverticulosis discomfort, when it exists, tends to be vague and comes and goes. Diverticulitis pain is persistent and localized, and pressing on the tender area makes it distinctly worse.
What Triggers an Episode
The exact trigger for a diverticulitis flare isn’t always clear. The traditional explanation is that stool or undigested food gets trapped in a pouch, causing a small tear and subsequent infection. More recent thinking points to additional factors: changes in the gut microbiome, altered immune responses in the colon wall, and chronic low-grade inflammation may all play a role. This helps explain why some people with extensive diverticulosis never have an episode while others with just a few pouches develop recurrent flares.
How Each Is Diagnosed
Diverticulosis usually requires no dedicated diagnostic workup. It shows up on colonoscopy as visible pouches in the colon wall, and the finding is simply noted in your report.
Diverticulitis, on the other hand, is typically diagnosed with a CT scan. The scan can reveal inflamed pouches, abscesses, fistulas, or other complications that determine how aggressive treatment needs to be. A colonoscopy is generally not performed during an active flare because of the risk of worsening a perforation. Instead, your doctor will typically recommend a follow-up colonoscopy six weeks or more after symptoms resolve to rule out other conditions like colorectal cancer, particularly if you haven’t had one recently or if the episode was severe.
Treatment for Diverticulitis
Diverticulosis doesn’t require treatment. It’s a structural finding, not an active problem. The focus with diverticulosis is prevention: keeping the colon healthy so those pouches don’t become inflamed.
Mild, uncomplicated diverticulitis is increasingly treated without antibiotics in otherwise healthy people. Current guidelines from the American Gastroenterological Association support using antibiotics selectively rather than routinely for patients with intact immune systems and mild symptoms. This is a significant shift from earlier practice, where antibiotics were considered standard. For people who are immunocompromised, antibiotic treatment remains strongly recommended.
During a flare, you’ll likely be advised to follow a low-fiber diet of around 10 to 15 grams of fiber per day until symptoms settle. This gives the colon time to heal without the mechanical stress of bulky stool moving through the inflamed area. Once the flare resolves, you gradually reintroduce high-fiber foods, aiming to reach 30 to 35 grams of fiber per day. That long-term fiber target is part of keeping the colon functioning well and reducing the chance of future episodes.
Complicated diverticulitis, meaning cases with an abscess, fistula, or perforation, sometimes requires drainage procedures or surgery. Most people with uncomplicated diverticulitis recover at home within a week or two.
Reducing Your Risk of Flares
If you have diverticulosis and want to minimize the chance of developing diverticulitis, the evidence points to a handful of lifestyle factors. A high-quality diet rich in fiber, maintaining a healthy body weight, staying physically active, and not smoking all reduce recurrence risk. Avoiding nonsteroidal anti-inflammatory drugs like ibuprofen and naproxen also helps, as these medications can irritate the colon lining and may increase the likelihood of a flare. Low-dose aspirin prescribed for heart protection is generally considered acceptable.
The old advice to avoid nuts, seeds, and popcorn has largely been abandoned. There’s no good evidence that these foods trigger diverticulitis, and restricting them unnecessarily can make it harder to reach your daily fiber goals.