Symptoms of Diverticulitis: What It Feels Like and What to Do

Medical Conditions · By Web Admin · · Updated · 11 min read
Symptoms of Diverticulitis: What It Feels Like and What to Do

Some diverticulitis is a medical emergency. Call 911 or go to the nearest emergency room for severe or rapidly worsening abdominal pain (usually in the lower left belly), a high fever with chills, a rigid or board-like abdomen, signs of shock (rapid pulse, low blood pressure, confusion), heavy rectal bleeding, or an inability to keep fluids down because of persistent vomiting. These can be signs of a perforation (a hole in the colon), an abscess, or peritonitis (a widespread abdominal infection), which need urgent treatment. Also seek prompt care if diverticulitis symptoms are not improving after a couple of days of treatment. Do not try to push through severe abdominal pain at home.

A sudden, sharp pain in the lower left side of your abdomen that worsens over hours — this is the calling card of diverticulitis, one of the most common gastrointestinal conditions affecting older adults. The symptoms of diverticulitis send well over 200,000 Americans to the hospital each year, making it one of the top reasons for inpatient GI care in the United States. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), diverticular disease becomes far more common with age, affecting a majority of adults by their 60s. Most people with diverticula (small pouches in the colon wall) never develop problems — but when one of those pouches becomes inflamed or infected, the result can range from a treatable nuisance to a surgical emergency. Here is what diverticulitis feels like, how it differs from other conditions like IBS and Crohn’s disease, and when to act. This article is part of our medical conditions guide and is general education, not medical advice.

Quick Summary

Diverticulitis happens when small pouches in the colon wall (diverticula) become inflamed or infected. The hallmark is lower-left-abdominal pain that builds over hours and turns constant, usually with low-grade fever, nausea, and a change in bowel habits (constipation more often than diarrhea). Most cases are uncomplicated and improve with rest, a temporary diet change, and — when a clinician decides they are needed — antibiotics. Complicated cases (abscess, perforation, peritonitis, obstruction) are emergencies. Two things have changed in recent guidance: antibiotics are now used selectively rather than routinely for mild cases, and the old warning to avoid nuts and seeds has been disproven.

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This article is for general education only and is not medical advice. Any severe or worsening abdominal pain should be evaluated in person. In an emergency, call 911.

What Is Diverticulitis?

To understand diverticulitis, you first need to understand diverticulosis. Diverticula are marble-sized pouches that bulge outward through weak spots in the colon wall, most commonly in the sigmoid colon (the S-shaped section in the lower left abdomen). Simply having these pouches is called diverticulosis — and by itself it is harmless. Most people with diverticulosis never develop symptoms.

Diverticulitis occurs when one or more of these pouches becomes inflamed or infected. The exact mechanism is debated, but the current understanding is that micro-perforations in a pouch allow bacteria to invade the surrounding tissue, triggering an inflammatory response. This can range from mild localized inflammation (uncomplicated diverticulitis) to abscess formation, perforation, peritonitis, or fistula development (complicated diverticulitis). The Mayo Clinic notes that only a minority of people with diverticulosis will ever develop diverticulitis.

Classic Symptoms of Diverticulitis

Left lower quadrant abdominal pain is the hallmark symptom, present in the large majority of Western patients. (In Asian populations, right-sided diverticulitis is more common due to differences in where diverticula tend to form.) The pain typically begins gradually, builds over several hours, and becomes constant rather than coming and going. It is often described as a deep ache or tenderness that worsens with movement, coughing, or pressing on the area.

Beyond the characteristic pain, diverticulitis commonly produces:

  • Fever — usually low-grade in uncomplicated cases, higher in complicated disease
  • Changes in bowel habits — constipation is more common than diarrhea, though both occur
  • Nausea and vomiting, particularly if the inflammation is significant
  • Abdominal bloating and increased gas
  • Loss of appetite
  • Urinary symptoms — frequency, urgency, or pain during urination if the inflamed colon irritates the adjacent bladder

Heavy rectal bleeding is uncommon in acute diverticulitis (brisk bleeding is more associated with diverticular bleeding, a separate condition), but a small amount of blood may be present. According to research indexed on PubMed, a notable minority of patients with acute diverticulitis present with atypical symptoms that can delay diagnosis, which is one more reason to get evaluated rather than self-diagnose.

Uncomplicated vs Complicated Diverticulitis

This distinction drives treatment decisions. Uncomplicated diverticulitis — the large majority of cases — involves localized inflammation without abscess, perforation, or obstruction. Symptoms are unpleasant but manageable: moderate pain, low-grade fever, and mild digestive disruption. Most uncomplicated cases resolve with conservative treatment within about 7 to 10 days.

Complicated diverticulitis is a different situation entirely. It includes abscess formation (a walled-off pocket of infection), free perforation (a hole in the colon allowing intestinal contents to leak into the abdominal cavity), peritonitis (widespread abdominal infection), fistula formation (an abnormal connection between the colon and the bladder, vagina, or skin), and bowel obstruction. These complications produce more severe symptoms: high fever, severe abdominal rigidity, a rapid heart rate, signs of sepsis, and, in the case of a colovesical fistula, air or stool in the urine. Complicated diverticulitis is the reason the emergency red flags above matter so much.

Risk Factors: Who Gets Diverticulitis?

Age remains the strongest risk factor — the likelihood increases significantly after 40, with most cases occurring in people over 50. However, diverticulitis is increasingly being diagnosed in younger adults, a trend that has risen steadily over the past two decades. Research from the NIDDK and multiple surgical studies suggests that younger patients may experience more aggressive disease with higher rates of complicated presentations. The reasons for rising diverticulitis in younger populations likely include increasing obesity rates, more sedentary lifestyles, dietary shifts toward processed foods, and greater diagnostic sensitivity from wider CT scan use.

Other established risk factors include obesity, a sedentary lifestyle, smoking (which raises the risk of complicated disease), regular use of NSAIDs (ibuprofen, naproxen) or corticosteroids, and a low-fiber diet — the “Western diet” hypothesis has been central to diverticular disease research for decades. Contrary to a persistent myth still circulated online and by some older practitioners, there is no good evidence that eating nuts, seeds, or popcorn triggers diverticulitis. A large prospective study of men, published in a major medical journal, actually found no increase — and if anything an inverse relationship — between nut and popcorn consumption and diverticulitis risk. Genetics also plays a role, with twin studies suggesting meaningful heritability for diverticular disease, indicating that familial predisposition contributes to who develops diverticula.

Diagnosis: What Your Doctor Will Do

The clinical picture — left lower quadrant pain with fever and an elevated white blood cell count — often raises immediate suspicion. However, a CT scan of the abdomen and pelvis with contrast is the gold-standard diagnostic test, with very high sensitivity and specificity for diverticulitis. The CT can confirm the diagnosis, assess severity (using the Hinchey classification for complicated disease), identify complications, and rule out alternative diagnoses including colorectal cancer, ovarian conditions, and appendicitis.

Blood work typically shows an elevated white blood cell count (leukocytosis) and elevated C-reactive protein (CRP), and markedly high CRP can point toward complicated disease. Urinalysis may be ordered if urinary symptoms are present, particularly to check for a colovesical fistula — air in the urine (pneumaturia) or stool particles in the urine (fecaluria) are telltale signs. Colonoscopy is generally avoided during the acute phase because of perforation risk, but it is commonly recommended roughly 6 to 8 weeks after recovery to rule out colorectal cancer, which can mimic diverticulitis on imaging. The American Society for Gastrointestinal Endoscopy supports this follow-up colonoscopy after a first episode, particularly for people over 50 or with other colorectal-cancer risk factors, unless a recent quality colonoscopy makes it unnecessary.

Treatment and Recovery

Uncomplicated diverticulitis is increasingly managed on an outpatient basis, with studies showing comparable outcomes to inpatient treatment for appropriately selected patients. Importantly, guidance from the American Gastroenterological Association (AGA) has moved toward selective rather than routine antibiotic use for mild, uncomplicated cases — a significant shift based on randomized trials that found no clear benefit of antibiotics over supportive care for CT-confirmed uncomplicated diverticulitis with minimal symptoms in otherwise healthy patients. That does not mean antibiotics are never used; it means the decision is individualized by a clinician based on how sick you are and your risk factors. When antibiotics are prescribed for outpatient care, typical options include a combination such as ciprofloxacin with metronidazole, or amoxicillin-clavulanate, for a course your clinician determines. Do not self-prescribe, borrow, or self-dose antibiotics — the choice, dose, and duration are medical decisions.

Supportive treatment during a flare centers on bowel rest and diet. Clinicians commonly advise starting with clear liquids and advancing to low-fiber foods as symptoms improve over a few days, using acetaminophen rather than NSAIDs for pain (NSAIDs may increase perforation risk), and resting. Once the acute episode resolves, patients gradually transition back to a high-fiber diet over several weeks. The old blanket instruction to permanently avoid nuts, seeds, and popcorn is no longer recommended.

Complicated diverticulitis requires hospitalization. Small abscesses may resolve with IV antibiotics alone; larger abscesses typically require CT-guided percutaneous drainage. Perforation with peritonitis necessitates emergency surgery — often a Hartmann procedure (removal of the diseased segment with a temporary colostomy) or, in select cases, primary resection with reconnection. Elective surgery (sigmoid colectomy) may be considered for some patients with recurrent episodes, though the threshold for operating has shifted upward in recent years and is now an individualized decision. If you are managing recurrent diverticulitis, a gastroenterologist can help develop a long-term plan.

Diverticulitis and the GI Condition Cluster

Diverticulitis exists within a broader landscape of gastrointestinal conditions that share overlapping symptoms and risk factors. Patients with diverticular disease are sometimes initially misdiagnosed with IBS, and conversely, some IBS diagnoses may actually represent symptomatic uncomplicated diverticular disease (SUDD) — a recognized entity in which diverticula cause chronic symptoms without acute inflammation. The relationship between these conditions remains an active area of research.

Crohn’s disease occasionally mimics diverticulitis, particularly when it involves the sigmoid colon. The key differentiators are the age of onset (Crohn’s typically presents younger), the pattern of inflammation (Crohn’s is transmural with skip lesions; diverticulitis is centered around diverticula), and extraintestinal features seen in Crohn’s. A follow-up colonoscopy after diverticulitis recovery helps exclude Crohn’s and colorectal cancer. For patients managing multiple GI conditions or seeking specialist evaluation, finding a gastroenterologist with expertise in diverticular disease supports the most accurate diagnosis and treatment.

Prevention: Reducing Your Risk of Recurrence

After a first episode of diverticulitis, a meaningful share of patients — roughly a fifth to a third — will have a recurrence over the following years. Lifestyle changes can reduce that risk. A high-fiber diet (aiming for roughly 25 to 35 grams daily from fruits, vegetables, whole grains, and legumes) is the most consistently supported preventive measure, best introduced gradually and with plenty of fluids. Regular physical activity — at least 150 minutes per week of moderate exercise — has been associated with lower diverticulitis risk in large observational studies.

Maintaining a healthy weight, not smoking, limiting red meat, and minimizing NSAID use are all supported by evidence. Some gastroenterologists consider probiotics or the anti-inflammatory medication mesalamine for recurrence prevention, though the evidence for these is mixed and they are not standard. Aspirin is a nuanced case: while NSAIDs in general are linked to higher risk, low-dose aspirin prescribed for cardiovascular protection involves a risk-benefit tradeoff that should be discussed with your doctor rather than stopped on your own.

Frequently Asked Questions

How long does a diverticulitis flare last?

Uncomplicated diverticulitis typically improves within 2 to 3 days of starting treatment, with fuller resolution in about 7 to 10 days. Complicated cases requiring hospitalization or drainage may take several weeks. If symptoms persist beyond roughly 72 hours of outpatient treatment, or if they worsen, contact your doctor — you may need CT imaging to check for complications.

Can I prevent diverticulitis with diet alone?

A high-fiber diet is the single most important dietary factor for prevention, but it works best combined with regular exercise, a healthy weight, and adequate hydration. There is no guaranteed way to prevent diverticulitis, but these factors together reduce risk substantially. The old advice to avoid nuts and seeds has been disproven and is no longer recommended.

Is diverticulitis the same as diverticulosis?

No. Diverticulosis simply means you have diverticula (small pouches) in your colon — a very common and usually harmless condition. Diverticulitis means one or more of those pouches has become inflamed or infected, causing symptoms that require treatment. Think of diverticulosis as the underlying anatomy and diverticulitis as the complication.

Do I always need antibiotics for diverticulitis?

Not necessarily. For mild, uncomplicated diverticulitis in otherwise healthy people, current guidance supports using antibiotics selectively rather than automatically, because trials found supportive care alone worked comparably for many such cases. Antibiotics remain important for complicated disease and for people who are more unwell or higher risk. This is a decision for your clinician — do not start or stop antibiotics on your own.

Can diverticulitis be confused with other conditions?

Yes. Left-sided diverticulitis can be confused with IBS, colorectal cancer, ovarian conditions in women, or urinary tract problems. Right-sided diverticulitis can mimic appendicitis. This is why CT imaging is important — symptoms alone are not reliable for diagnosis, particularly in younger patients where diverticulitis may not be the first condition suspected.

What to Do Next

If you are experiencing lower-left abdominal pain with fever, do not wait to see if it passes. Contact your primary care provider or visit an urgent care facility that can order blood work and a CT scan. Early diagnosis of uncomplicated diverticulitis allows for outpatient treatment and a much faster recovery. Treat the emergency red flags — severe or worsening pain, high fever, a rigid abdomen, heavy bleeding, or inability to keep fluids down — as reasons to go to the ER now. After recovery, schedule a follow-up colonoscopy if your doctor recommends one, increase your fiber intake gradually, and commit to regular physical activity. These proactive steps reduce the likelihood that diverticulitis becomes a recurring problem.

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