Diverticulitis: Causes, Symptoms, and Treatment

By age 60, more than half of Americans have diverticulosis — small pouches that form in the walls of the colon. Most never cause problems. But when one or more of those pouches becomes inflamed or infected, the result is diverticulitis, a condition that accounts for roughly 200,000 or more hospital admissions in the United States each year. Diverticulitis can range from a mild, manageable flare treated at home to a serious emergency requiring surgery. Knowing the difference — and understanding your treatment options — matters. This guide is educational and is not a substitute for care from a qualified clinician. For an overview of how digestive conditions connect to broader health, visit our medical conditions guide.

Diverticulosis vs. Diverticulitis: Understanding the Difference

Diverticulosis refers simply to the presence of diverticula — small, bulging pouches that push outward through weak spots in the colon wall, most commonly in the sigmoid colon (the S-shaped section just above the rectum). According to the NIDDK, diverticulosis is extremely common and is generally considered a normal finding related to aging. Most people with diverticulosis are asymptomatic and will never need treatment. It is frequently discovered incidentally during a colonoscopy done for another reason.

Diverticulitis occurs when one or more diverticula become inflamed or infected. Older teaching held that this happens in 10 to 25 percent of people with diverticulosis, though more recent estimates suggest the lifetime risk of a symptomatic attack may be lower — on the order of 5 percent or less over many years — because so many people with pouches never develop problems. The inflammation can be uncomplicated (localized inflammation without abscess, perforation, or other structural damage) or complicated (involving abscess formation, perforation, fistula, or bowel obstruction). The large majority of acute diverticulitis cases — roughly three in four — are uncomplicated.

The umbrella term “diverticular disease” encompasses both diverticulosis and diverticulitis, as well as diverticular bleeding — a separate complication where a blood vessel adjacent to a diverticulum erodes and bleeds, sometimes profusely and usually painlessly. Understanding this spectrum helps clarify what your doctor means when discussing your diagnosis, because the pouches, an infection of the pouches, and bleeding from the pouches are three different situations with different management.

What Causes Diverticulitis?

The exact mechanism that triggers inflammation in a diverticulum is still debated. The traditional theory held that a piece of hardened stool (a fecalith) became trapped in a diverticulum, blocking its narrow opening and creating a micro-environment where bacteria could proliferate. More recent research suggests the process is more complex, likely involving alterations in the colonic microbiome, low-grade chronic inflammation, localized ischemia (reduced blood flow), and changes in colonic motility. Diverticulitis is increasingly viewed as an inflammatory process, not simply a mechanical infection — which is part of why antibiotics are no longer considered automatic for every case.

The formation of diverticula themselves is linked to increased pressure within the colon. A low-fiber diet leads to smaller, harder stools that require more forceful muscular contractions to move through the colon. Over time, this elevated intraluminal pressure pushes the inner lining of the colon through weak points in the muscular wall, creating diverticula. This helps explain why diverticular disease has historically been far more common in Western countries with low-fiber diets, although genetics and other factors clearly matter too.

Risk factors for developing diverticulitis specifically include aging, obesity (particularly abdominal obesity), physical inactivity, smoking, a diet low in fiber and high in red meat, and regular use of NSAIDs, opioids, or corticosteroids. Genetics also play a substantial role — twin studies suggest that roughly 40 to 50 percent of the susceptibility to diverticular disease is heritable, so a strong family history is a meaningful risk factor.

Recognizing the Symptoms

The hallmark symptom of diverticulitis is pain in the lower-left abdomen. Because most diverticula develop in the sigmoid colon, which sits in the left lower quadrant, this is where inflammation is typically felt. However, in people of East Asian descent, right-sided diverticula (and therefore right-sided pain) are more common, which can make the diagnosis harder to distinguish from appendicitis. The pain is usually constant rather than crampy and may develop gradually or come on suddenly.

According to the Mayo Clinic, other common symptoms include fever, nausea, vomiting, abdominal tenderness, changes in bowel habits (constipation is more common than diarrhea), bloating, and occasionally urinary symptoms if the inflamed colon irritates the bladder. Mild cases may present with only dull, persistent left lower quadrant discomfort and a low-grade fever, which is one reason mild attacks are sometimes mistaken for a passing stomach upset.

The red-flag box at the top of this article lists the warning signs that call for emergency evaluation. In short, severe or worsening pain, a high fever, a rigid abdomen, an inability to keep fluids down, or significant rectal bleeding should never be managed at home — they can indicate a perforation, an abscess, or another complication that needs urgent imaging and treatment.

How Diverticulitis Is Diagnosed

Diagnosis begins with a clinical assessment — your symptoms, physical examination findings (particularly tenderness in the left lower abdomen), vital signs, and blood work. An elevated white blood cell count and elevated C-reactive protein support the diagnosis but are not specific. The American College of Gastroenterology recommends CT of the abdomen and pelvis with intravenous contrast as the diagnostic study of choice for a suspected acute attack. CT imaging is highly sensitive for diverticulitis and, importantly, can identify complications such as abscesses, fistulas, and free air that indicates perforation — findings that directly change treatment.

Ultrasound may be used as an initial test in some settings, particularly in Europe and in patients where radiation exposure is a concern (such as younger adults or pregnant women), though it is more operator-dependent than CT. Colonoscopy is generally avoided during an acute flare because of the risk of perforation, but it is typically recommended several weeks after recovery — often around six to eight weeks — to inspect the colon and rule out colorectal cancer, which can occasionally masquerade as diverticulitis. This is especially important if you have not had a recent, up-to-date screening. For more on screening, see our guide on colorectal cancer.

Importantly, diverticulitis must be distinguished from other conditions that cause similar symptoms, including irritable bowel syndrome, inflammatory bowel disease, colorectal cancer, ovarian pathology in women, appendicitis, and urinary tract infections. The CT scan is instrumental in making this differential diagnosis accurately, which is another reason self-diagnosis of “another diverticulitis attack” can be misleading — not every episode of left-sided belly pain is diverticulitis.

Treatment of Uncomplicated Diverticulitis

Uncomplicated diverticulitis — meaning inflammation without abscess, perforation, fistula, or obstruction — is increasingly managed on an outpatient basis in people who are otherwise well, can stay hydrated, and have someone to watch for warning signs. Recent evidence has shifted treatment paradigms significantly. Randomized trials found that many patients with mild, uncomplicated diverticulitis recover without antibiotics, challenging the long-held assumption that antibiotics were always necessary.

The most important 2026 update: current guidance from the American Gastroenterological Association supports using antibiotics selectively rather than routinely for uncomplicated diverticulitis in appropriately selected patients. This does not mean you should decide on your own to skip antibiotics. It means a clinician evaluates you and decides. People who are immunocompromised, older or frail, pregnant, have significant other illnesses, show signs of systemic infection, or have more concerning imaging findings should still receive antibiotics. When antibiotics are prescribed, they are chosen and dosed by your clinician; this guide deliberately does not list specific medicines or doses, because antibiotic selection depends on your individual situation, allergies, and local resistance patterns.

Supportive care includes rest, adequate hydration, and a temporary change in diet during the acute phase (discussed below), with a gradual return to a normal diet as symptoms improve. For pain, acetaminophen is generally preferred; NSAIDs such as ibuprofen and naproxen are usually discouraged during and around a flare because they are associated with a higher risk of complications. Most patients with uncomplicated diverticulitis begin improving within a few days and recover over one to two weeks. If you are not clearly getting better after two to three days, that is a reason to be reassessed — imaging may need to be repeated.

Managing Complicated Diverticulitis

Complicated diverticulitis requires more aggressive intervention and usually hospital care. Diverticular abscesses — pockets of infected fluid near the inflamed colon — are often described using the Hinchey classification. Small abscesses may resolve with intravenous antibiotics alone. Larger abscesses typically require CT-guided percutaneous drainage, in which a radiologist inserts a thin tube through the skin to drain the infected fluid, combined with antibiotics.

Free perforation — a hole in the colon wall allowing intestinal contents to spill into the abdominal cavity — is a surgical emergency. This typically requires urgent surgery to remove the affected segment of colon. The traditional approach is a Hartmann procedure, in which the diseased segment is resected, the rectal stump is closed, and a temporary colostomy is created. In selected cases, a primary anastomosis (reconnecting the bowel ends), with or without a protective ileostomy, may be feasible; the choice depends on how sick the patient is and how contaminated the abdomen is.

Fistulas — abnormal connections between the colon and adjacent organs such as the bladder (colovesical fistula) or vagina (colovaginal fistula) — almost always require surgical repair. Colovesical fistulas classically present with recurrent urinary tract infections, air in the urine (pneumaturia), or passage of stool-like material in the urine. Bowel obstruction from diverticular strictures may require endoscopic dilation or surgical resection depending on severity and how urgently it develops.

When Surgery Is Recommended

Elective surgery for diverticulitis — specifically sigmoid colectomy (removal of the sigmoid colon) — was once recommended almost automatically after two episodes of uncomplicated diverticulitis. That rigid “number-of-episodes” rule has been largely abandoned. Current practice individualizes the surgical decision based on the severity and impact of episodes, the patient’s age, overall health, immune status, and quality of life.

The American Society of Colon and Rectal Surgeons generally reserves elective surgery for patients who have had complicated disease (such as an abscess, fistula, or stricture), immunosuppressed patients at higher risk for perforation, and patients whose recurrent episodes significantly impair their quality of life. Surgery is not recommended solely because someone has crossed a particular count of uncomplicated episodes; it is a shared decision that weighs the risks of repeated attacks against the risks of an operation.

Laparoscopic (minimally invasive) sigmoid colectomy is the preferred technique when surgery is elective, offering less pain, shorter hospital stays, and faster recovery than open surgery. The diseased sigmoid colon is removed and the remaining colon is reconnected to the upper rectum. A permanent colostomy is rarely needed in the elective setting, and long-term outcomes after planned surgery are generally excellent, though no operation eliminates every future risk.

Diet by Phase: What to Eat and When

Diet in diverticular disease is easiest to understand in phases, because the right food during an acute attack is the opposite of the right food for long-term prevention.

During an acute flare, many clinicians advise resting the bowel with clear liquids (water, broth, clear juices, gelatin) for a short period, then advancing to low-fiber, easy-to-digest foods as symptoms ease. This is a temporary measure to reduce discomfort while the inflammation settles — not a long-term diet. Follow the specific instructions your own clinician gives you, since mild cases may not need such strict restriction.

After recovery, the goal flips. A high-fiber diet is the most consistently supported strategy to reduce the risk of future problems. The NIDDK and dietary guidelines generally point toward roughly 25 to 35 grams of fiber daily from fruits, vegetables, whole grains, and legumes, though the exact target should be tailored to you. Increase fiber gradually and drink plenty of water, because adding fiber too quickly can cause gas and bloating.

A key myth, debunked: the longstanding recommendation to avoid nuts, seeds, popcorn, and corn has not held up. A large prospective study published in the Journal of the American Medical Association found that men who ate the most nuts and popcorn actually had a lower, not higher, risk of diverticulitis. There is no good evidence that these foods lodge in diverticula or trigger attacks. Modern guidelines from major gastroenterology societies no longer recommend avoiding them, so you do not need to fear a handful of nuts or a bowl of popcorn once you have recovered.

Preventing Recurrence

Beyond fiber, several lifestyle measures are linked to a lower risk of diverticulitis in observational studies. Regular physical activity — for many people, at least 30 minutes of moderate exercise on most days — is associated with meaningfully reduced risk. Maintaining a healthy weight, not smoking, limiting red and processed meat, and minimizing regular NSAID use (with your clinician’s input if you take them for another condition) are additional evidence-based strategies. Some physicians discuss daily fiber supplements or probiotics, though the evidence for probiotics specifically remains mixed and inconsistent.

Investing in prevention has a practical financial upside too. A fiber-rich diet and regular exercise cost little compared with an emergency room visit, a CT scan, a hospital stay, or surgery. If cost or coverage is a worry, our healthcare costs guide outlines options for managing medical expenses and getting proactive care before a flare becomes an emergency.

Frequently Asked Questions

Can diverticulitis go away on its own?

Mild, uncomplicated diverticulitis can improve without antibiotics in many people, with rest, hydration, a temporary diet change, and acetaminophen for pain. But that decision belongs to a clinician after an evaluation — not to self-diagnosis. A proper assessment is needed to confirm it really is diverticulitis and to rule out complications that require specific treatment. Even when antibiotics are not prescribed, medical monitoring during a flare is important.

Is diverticulitis a lifelong condition?

Diverticulosis — the underlying pouches — is permanent, because the pouches do not disappear once formed. But having diverticulosis does not mean you will get diverticulitis, and many people never do. Among those who have one episode of diverticulitis, a meaningful minority will have a recurrence, but with dietary and lifestyle management — and, in selected cases, surgery — many people go on to have few or no further flares.

What foods should I avoid with diverticulitis?

During an active flare, your doctor will likely recommend clear liquids and then low-fiber foods for a short time while symptoms settle. Once recovered, the goal is the opposite — a high-fiber diet to help prevent recurrence. You do not need to avoid nuts, seeds, popcorn, or corn, since that old restriction has been debunked. Limiting red and processed meat and heavily processed “Western” diet patterns may be beneficial based on observational studies.

How do I know if my diverticulitis is serious?

Warning signs of complicated or severe disease include a high fever, severe or worsening abdominal pain despite treatment, an inability to keep fluids down, a rigid abdomen, heavy rectal bleeding, or symptoms of a fistula (air or stool in the urine, or passage of gas or stool from the vagina). If you were diagnosed with uncomplicated diverticulitis and are not improving within two to three days, contact your clinician for reassessment — imaging may need to be repeated. When in doubt about severe symptoms, seek emergency care.

Can young people get diverticulitis?

Yes. While diverticular disease is most common in people over 50, diverticulitis has become more frequent among adults under 40 in recent decades, a trend often linked to rising obesity rates and dietary changes. Younger patients were once thought to have a uniformly more aggressive disease course, but more recent data challenge that assumption. Treatment for younger adults follows the same individualized approach used for older adults.

Does drinking more water or eating fiber help during an attack?

Staying hydrated is always sensible, but loading up on fiber in the middle of an acute flare is usually not advised — that is when clinicians often recommend resting the bowel with a lighter, lower-fiber diet. Fiber is a prevention tool for after you have recovered, not a treatment for the acute attack itself. Follow your clinician’s phase-specific instructions.

Living With Diverticular Disease: What to Do Next

If diverticulosis was found on a routine colonoscopy, there is no need for alarm — but there is an opportunity to take preventive action. Gradually increase your fiber intake, stay physically active, maintain a healthy weight, and drink plenty of water to complement the higher fiber in your diet.

If you have experienced diverticulitis, work with your doctor on a plan for managing flares and preventing new ones. Know which warning signs warrant a call to your physician versus a trip to the emergency room. Ask about scheduling a follow-up colonoscopy if one has not been done recently, and discuss whether elective surgery makes sense in your particular situation, especially if you have had complicated disease or frequent recurrences that affect daily life.

Keep the big picture in mind: diverticular disease is manageable for the vast majority of people. Most people with diverticulosis never develop diverticulitis, most people who have one episode recover fully with conservative treatment, and even those who need surgery generally do well long-term. The condition calls for awareness and proactive management — not fear.

Sources

• NIDDK (National Institute of Diabetes and Digestive and Kidney Diseases), Diverticular Disease — niddk.nih.gov
• Mayo Clinic, Diverticulitis: Symptoms and Causes — mayoclinic.org
• American Gastroenterological Association (AGA), Clinical Guidance on Acute Diverticulitis — gastro.org
• American College of Gastroenterology (ACG), Diverticulosis and Diverticulitis Guideline — gi.org
• American Society of Colon and Rectal Surgeons (ASCRS), Clinical Practice Guidelines for Left-Sided Colonic Diverticulitis — fascrs.org