Diverticulitis occurs when one or more small pouches that commonly develop in the wall of the colon become inflamed or infected. These pouches, called diverticula, are extremely common as people age and, on their own, cause no problems at all — a condition known as diverticulosis. Diverticulitis is different: it is what happens on the occasions when a pouch becomes irritated, leading to abdominal pain and sometimes a more serious infection that needs medical care. Most cases are manageable, and treatment has shifted significantly in recent years toward gentler, more individualized approaches. This guide explains what diverticulitis is, its symptoms, causes, how it is diagnosed, the treatments available, and the latest research.
What is diverticulitis?
Diverticulosis develops when small pouches, called diverticula, push outward through weak points in the muscular wall of the colon, most often in the sigmoid colon on the lower left side of the abdomen. These pouches form over time from pressure inside the colon combined with age-related changes in its wall, and they are common: more than 30 percent of US adults ages 50 to 59 have them, rising to more than 70 percent of people over 80. Diverticulosis by itself is usually silent, so most people who have it never know unless it is spotted incidentally during a colonoscopy or a scan done for another reason.
Diverticulitis is what happens when one or more of these pouches become inflamed or, in many cases, infected. Fewer than 5 percent of people with diverticulosis ever develop diverticulitis, but it happens often enough to drive roughly 200,000 hospital admissions in the United States each year. Most episodes, around 80 to 85 percent, are uncomplicated, meaning the inflammation stays confined to the colon wall. The remaining 15 to 20 percent are complicated by an abscess, a perforation, a fistula, or a bowel blockage, problems that need closer monitoring and, sometimes, more intensive treatment. Recognizing which category a flare-up falls into is central to how it is managed.
Symptoms of diverticulitis
The hallmark symptom of diverticulitis is abdominal pain, usually sudden or steadily worsening and typically felt in the lower left side of the abdomen, where the sigmoid colon sits. The area is often tender to the touch, and the pain frequently comes with fever, nausea or vomiting, and a change in bowel habits such as constipation or diarrhea. Some people also notice bloating or a general feeling of being unwell. These symptoms can build over a day or two and are usually what prompts a visit to a doctor or urgent care.
Most flare-ups are uncomplicated and improve with prompt treatment, but certain symptoms point to a more serious, complicated case and call for emergency care. Warning signs that should never be ignored include severe or rapidly worsening pain, a high fever, an inability to keep down fluids, a rigid or extremely tender belly, or a fast heart rate, confusion, or dizziness suggesting a body-wide infection. Because a ruptured abscess or perforation can cause peritonitis, a life-threatening infection of the abdominal cavity, anyone with these red-flag symptoms should go to an emergency room rather than wait to see if the pain improves.
What causes diverticulitis and its risk factors
Diverticulitis is thought to begin when a diverticulum becomes blocked or its lining is injured, allowing bacteria to multiply and trigger inflammation or infection in the surrounding tissue. Age is the biggest risk factor, since diverticula themselves become more common with each decade of life, but other factors raise the odds of a flare-up too. A long-term diet low in fiber and high in red meat, obesity, smoking, and a sedentary lifestyle are all linked to higher risk, as is regular use of nonsteroidal anti-inflammatory drugs, steroids, or opioid pain medications. A family history of diverticulitis suggests that genetics play a role as well.
It helps to know that diverticulitis has a different root cause than other conditions that can produce similar colon symptoms. Diverticulitis does not share the immune system dysfunction that produces the bowel inflammation of Crohn’s disease or causes the colon inflammation of ulcerative colitis; it stems mainly from age-related structural changes in the colon combined with diet and lifestyle factors. That distinction matters for treatment, since diverticulitis usually responds to antibiotics, diet changes, or drainage rather than the long-term immune-targeted therapies used for inflammatory bowel disease.
How diverticulitis is diagnosed
A CT scan of the abdomen and pelvis, taken with contrast, is the gold standard for diagnosing diverticulitis, correctly identifying the condition and revealing complications such as an abscess, perforation, or fistula in most cases. The scan confirms the diagnosis and shows whether the case is uncomplicated or complicated, which shapes the treatment plan that follows.
| Diagnostic test | What it shows |
|---|---|
| CT scan of the abdomen and pelvis (with contrast) | Confirms diverticulitis and identifies complications such as an abscess, perforation, or fistula; the gold standard test |
| White blood cell count | A high count supports the presence of infection or inflammation |
| C-reactive protein (CRP) | Rises with inflammation; a sharp elevation raises suspicion for complicated disease |
| Fecal calprotectin | A stool marker of gut inflammation being studied to help flag flare-ups and recurrence |
| Colonoscopy (6 to 8 weeks later) | Examines the colon lining once inflammation has settled to rule out colorectal cancer or other conditions |
Two blood tests usually accompany the scan. Checking the leukocyte count on a blood test helps confirm that infection is present and factors into decisions about antibiotics or hospital care, while measuring the CRP level in the blood shows how much inflammation is present: a sharp elevation raises suspicion for complicated disease such as an abscess, while a smaller rise is typical of milder inflammation. Doctors are also studying the fecal calprotectin test, a stool marker of gut inflammation, as a non-invasive way to flag flare-ups and recurrence risk, though it is not yet routine in US practice. A colonoscopy performed 6 to 8 weeks after symptoms resolve looks directly at the lining to rule out the possibility of colorectal cancer or other conditions; it is delayed during an active attack because of the added perforation risk.
Treatment options for diverticulitis
Treatment for diverticulitis depends on whether the case is uncomplicated or complicated, and the overall approach has shifted toward less intervention for milder cases. For selected, healthy patients with uncomplicated diverticulitis and no signs of widespread infection, growing evidence supports skipping antibiotics in favor of close observation, a shift reflected in current guidance from the American Gastroenterological Association. Many mild flare-ups are managed at home with rest, pain control, and a temporary change in diet.
| Approach | Role |
|---|---|
| Observation without antibiotics | Appropriate for selected, healthy patients with mild, uncomplicated diverticulitis |
| Diet progression | Clear liquids rest the bowel during a flare, followed by a gradual return to fiber as symptoms ease |
| Antibiotics | Used for complicated disease or when fever, significant illness, or risk factors are present |
| Drainage or surgery | Drains a larger abscess or addresses perforation, uncontrolled infection, or obstruction |
During an acute flare, doctors often recommend a short period of clear liquids to rest the bowel, then a gradual return to low-fiber and, as symptoms ease, high-fiber foods; acetaminophen is generally preferred over NSAIDs for pain relief. The old advice to permanently avoid nuts, seeds, popcorn, and similar foods has been debunked by modern research: these foods are not linked to a higher flare-up risk and are, in fact, good fiber sources. Complicated diverticulitis, or any case with fever, significant illness, or a weakened immune system, still requires antibiotics; a larger abscess may need percutaneous drainage, and generalized peritonitis from a perforation is a surgical emergency. Current guidance advises against routine elective surgery after one uncomplicated episode, reserving that discussion for repeated or complicated flare-ups.
Living with diverticulitis and long-term outlook
Most people who recover from a diverticulitis flare-up go on to live normally, especially after an uncomplicated episode treated with rest, diet changes, and medication if needed. Because diverticula do not disappear once they form, some people have another flare-up, but many others never have a second episode. Staying on top of long-term habits, such as a high-fiber diet, regular exercise, a healthy weight, and not smoking, meaningfully lowers the chance of recurrence.
For some people, the digestive tract remains sensitive for a while after inflammation resolves, and it is not unusual to notice ongoing bloating, cramping, or unpredictable bowel habits that resemble the lingering symptoms of irritable bowel syndrome. Working with a doctor on a fiber plan and revisiting symptoms that do not settle is worthwhile. For anyone with a complicated episode or recurring attacks, ongoing follow-up helps determine whether observation, dietary management, or a conversation about surgery is the right long-term path.
Latest scientific advances in diverticulitis research
According to PubMed-indexed research, a 2025 quality-improvement study from a University of Colorado emergency department found that a formal clinical pathway and provider education cut oral antibiotic use for imaging-confirmed, uncomplicated diverticulitis, with no difference in 90-day emergency department returns, hospitalizations, drainage, or emergency surgery between the antibiotic and non-antibiotic groups (Lee et al., 2025). What this means for you: real-world US data now back what earlier trials suggested, that many well-selected, healthy patients with uncomplicated diverticulitis can safely skip antibiotics under a doctor’s guidance.
A 2026 systematic review and meta-analysis pooling more than 7,000 patients who initially improved with non-surgical treatment of a diverticular abscess found that elective colectomy afterward lowered the odds of diverticulitis recurring but nearly doubled the odds of needing a stoma compared with continued observation (Akbarpoor et al., 2026). What this means for you: removing the colon after an abscess resolves is a real trade-off between fewer repeat episodes and a higher chance of a stoma, and the choice should be individualized rather than routine. Separately, a 2025 study of more than 600 emergency department patients with acute diverticulitis found that both CRP and the neutrophil-lymphocyte ratio, calculated from a routine blood count, predicted who was likely to need surgery or drainage (Ho et al., 2025). What this means for you: CRP, an inexpensive and widely available blood test, remains a legitimate way to gauge how serious a flare-up is, and newer combined-biomarker approaches may sharpen that triage further.
Glossary of key diverticulitis terms
| Term | Definition |
|---|---|
| Diverticula | Small pouches that bulge outward through weak spots in the wall of the colon. |
| Diverticulosis | The presence of diverticula without inflammation or infection, usually causing no symptoms. |
| Diverticulitis | Inflammation or infection of one or more diverticula. |
| Uncomplicated diverticulitis | Inflammation confined to the colon wall, without an abscess, perforation, or other complication. |
| Complicated diverticulitis | Diverticulitis with an abscess, perforation, fistula, or bowel obstruction. |
| Sigmoid colon | The S-shaped final section of the large intestine, on the lower left side of the abdomen, where diverticula most often form. |
| Percutaneous drainage | A needle-based procedure, guided by imaging, that drains an abscess without open surgery. |
Frequently asked questions about diverticulitis
What is the difference between diverticulosis and diverticulitis?
Diverticulosis is the presence of small pouches, called diverticula, in the colon wall; it is common after age 50 and usually causes no symptoms. Diverticulitis is what happens when one or more of those pouches become inflamed or infected, causing pain, fever, and other symptoms that need medical attention. In short, diverticulosis is the pouches themselves, and diverticulitis is a flare-up of one of them.
What blood tests or scans are used to diagnose diverticulitis?
A CT scan of the abdomen and pelvis with contrast is the main test, showing whether an abscess, perforation, or fistula is present. A white blood cell count checks for infection, and CRP measures inflammation, with a sharp rise pointing toward a more complicated case. Colonoscopy is not done during an active flare-up, but it is scheduled 6 to 8 weeks later to examine the colon and rule out other causes.
Can diverticulitis go away on its own without antibiotics?
Yes, for many people with mild, uncomplicated diverticulitis, current guidance supports careful observation without antibiotics rather than automatic treatment. This approach is reserved for healthy patients without signs of widespread infection and is decided with a doctor once imaging confirms the case is uncomplicated. Complicated diverticulitis, or any case with a high fever or significant illness, still needs antibiotics.
What foods should I avoid — and can I really eat nuts, seeds, and popcorn?
Yes, nuts, seeds, popcorn, and similar foods are safe for most people with diverticulosis or a history of diverticulitis. The old advice to avoid them permanently has been debunked by modern research, which found no increased flare-up risk; in fact, they are good fiber sources. During an active flare, doctors typically recommend clear liquids and then low-fiber foods until symptoms ease, followed by a gradual return to a high-fiber diet.
When is diverticulitis a medical emergency, and when should I go to the ER?
Go to an emergency room for severe or rapidly worsening abdominal pain, a high fever, an inability to keep down fluids, or a belly that feels rigid or extremely tender. These can signal a complication such as a perforation or a spreading infection that needs prompt evaluation and sometimes emergency treatment. It is always better to be checked than to wait out symptoms that turn out to be serious.
Do I need surgery for diverticulitis, and what is the difference between elective and emergency surgery?
Most people never need surgery for diverticulitis. Emergency surgery is reserved for life-threatening complications, such as a perforation with peritonitis or an obstruction that will not resolve on its own. Elective surgery, done later under planned conditions, is considered for repeated complicated episodes or a recurring abscess, but current guidance no longer recommends it routinely after one uncomplicated episode, since the decision weighs fewer repeat episodes against real surgical risks.
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases — Symptoms & Causes of Diverticular Disease — NIDDK, 2021 — niddk.nih.gov
- Mayo Clinic — Diverticulitis — Mayo Clinic, 2023 — mayoclinic.org
- Cleveland Clinic — Diverticulitis — Cleveland Clinic Health Library, 2024 — my.clevelandclinic.org
- Lee JS, Carmichael H, Bellen BA, et al. — Outpatient Management of Acute Sigmoid Diverticulitis: Education and a Clinical Pathway Reduced Antibiotic Use Without Compromise in Clinical Outcomes — Diseases of the Colon & Rectum, 2025 — doi.org/10.1097/DCR.0000000000004006
- Akbarpoor F, Delgado LM, Aakef K, et al. — Elective Colectomy Versus Observation Following Initial Nonoperative Success in Hinchey Ib/II Diverticulitis: A Systematic Review and Meta-Analysis — The American Surgeon, 2026 — doi.org/10.1177/00031348261423926
- Ho YT, Perera OM, Ayeni FE, et al. — A Retrospective Study on Use of Neutrophil-Lymphocyte Ratio as a Prognostic Measurement to Assess Acute Diverticulitis — ANZ Journal of Surgery, 2025 — doi.org/10.1111/ans.70220
Further reading
- Explore a more sensitive marker of hidden inflammation in this guide to the hs-CRP test for silent inflammation.
- See how doctors check for hidden bleeding in this guide to the fecal occult blood test.
- Build confidence reading test results with this guide to reference ranges, flags, and next steps on a lab report.
Understand your lab results with BloodSense
Diverticulitis care depends on more than imaging alone: the white blood cell count, CRP, and emerging markers like fecal calprotectin help your care team judge how severe a flare-up is and whether it can be watched closely or needs more active treatment. Seeing where each value sits against its reference range, and how it shifts from one test to the next, makes results easier to act on with your doctor. BloodSense translates a full lab report into plain language, showing what each marker means and helping you track changes over time instead of reading one number in isolation.
