Diverticulitis

Diverticulosis vs diverticulitis

In Western countries, diverticula usually form in the sigmoid colon on the lower left side, which is why pain is typically on the left. In Asian populations, right-sided diverticula are more common, and diverticulitis can mimic appendicitis.

Causes and risk factors

Diverticula develop when pressure inside the colon pushes the inner lining through weak points where blood vessels pass through the muscle wall. Diverticulitis occurs when a pouch becomes inflamed, possibly from a tiny tear or changes in gut bacteria.

Risk factors include:

• Age: risk rises after 40
• Low-fiber diet and high intake of red and processed meat
• Obesity, especially abdominal fat
• Physical inactivity
• Smoking
• Medicines: NSAIDs, aspirin, opioids and steroids
• Genetics

Symptoms

• Abdominal pain: usually constant, lasting days, in the lower left abdomen. It may start as cramping and become sharper
• Tenderness when pressing the area
• Fever and chills
• Nausea and sometimes vomiting
• Change in bowel habits: constipation or diarrhea
• Bloating
• Urinary symptoms if the inflamed colon is next to the bladder

Older adults and people on steroids may have milder symptoms despite serious inflammation.

Uncomplicated vs complicated diverticulitis

Diagnosis

1. History and examination: location and duration of pain, fever, bowel changes, previous attacks.
2. Blood tests: white blood cell count and C-reactive protein (CRP) for inflammation.
3. Urine test and pregnancy test where relevant, to rule out other causes.
4. CT scan of the abdomen: the most accurate test. It confirms diverticulitis, grades its severity and detects abscess or perforation. In people with a previous confirmed diagnosis and mild typical symptoms, a scan is not always needed.
5. Colonoscopy: not done during an acute attack, but often recommended 6 to 8 weeks afterward, especially after complicated diverticulitis or if no recent colonoscopy has been done, to rule out colorectal cancer, which can look similar on CT.

Diverticulitis treatment

Uncomplicated diverticulitis at home

• Rest.
• Clear liquids for a few days if pain is significant, then gradually return to low-fiber foods, then a high-fiber diet once symptoms settle.
• Pain relief: acetaminophen (paracetamol). Avoid NSAIDs such as ibuprofen and opioids where possible, as they are linked with complications.
• Antibiotics: current guidelines from the AGA and ACP say antibiotics can be used selectively rather than routinely in healthy people with mild, uncomplicated diverticulitis. They are recommended for people who are older, frail, immunocompromised, have significant other illnesses, high fever, or do not improve.
• Follow-up within a few days to check improvement.

Hospital treatment

Needed for severe pain, inability to drink, complications, weakened immunity or failure to improve:

• IV fluids and IV antibiotics
• Bowel rest
• Abscess drainage: larger abscesses (generally over 3 to 4 cm) are drained with a needle guided by CT
• Emergency surgery for perforation with peritonitis or uncontrolled sepsis

Surgery

• Emergency surgery may involve removing the affected colon and sometimes a temporary colostomy (Hartmann's procedure), or a primary repair in suitable patients.
• Elective surgery to remove the sigmoid colon is no longer recommended automatically after 2 attacks. It is considered for people with frequent attacks affecting quality of life, persistent symptoms, fistula, stricture, or weakened immunity. It is often done by keyhole surgery.

Diverticulitis diet

During a flare

• Start with clear liquids (water, broth, clear juices, gelatin) if advised
• Progress to low-fiber foods (white bread, rice, eggs, cooked vegetables without skins) as pain eases

For long-term prevention

• High-fiber diet: aim for 25 to 35 grams a day from fruit, vegetables, whole grains, beans and lentils. Increase gradually and drink plenty of water
• Fiber supplements such as psyllium if diet alone is not enough
• Limit red and processed meat

Complications and outlook

Most people recover from an uncomplicated attack within 1 to 2 weeks. About 1 in 5 have another attack within the next several years, and recurrences are usually not more severe than the first. Complicated diverticulitis has a higher risk of recurrence and may lead to surgery.

Prevention

• Eat a high-fiber diet
• Exercise regularly
• Maintain a healthy weight
• Don't smoke
• Limit NSAIDs and opioids where possible
• Treat constipation

Frequently asked questions

What are the symptoms of diverticulitis?

The main symptoms are constant pain in the lower left abdomen, fever, nausea, and constipation or diarrhea. The area is tender to press. Severe pain, a rigid belly, high fever or rectal bleeding suggest complications and need urgent care.

What foods should I avoid with diverticulitis?

During a flare, temporarily avoid high-fiber foods and follow clear liquids, then low-fiber foods as advised. Long term, a high-fiber diet is recommended. You do not need to avoid nuts, seeds or popcorn; research shows they do not trigger attacks. Limiting red meat may help.

Do you always need antibiotics for diverticulitis?

Not always. Guidelines now say healthy people with mild, uncomplicated diverticulitis can often recover without antibiotics. They are recommended for older or frail people, those with weakened immunity, complications, high fever or symptoms that do not improve.

What causes a diverticulitis flare?

The exact trigger is uncertain. It may involve a small tear or blockage in a pouch and changes in gut bacteria. Low-fiber diets, obesity, inactivity, smoking and medicines such as NSAIDs and opioids increase the risk.

When does diverticulitis need surgery?

Emergency surgery is needed for perforation, peritonitis or uncontrolled infection. Planned surgery may be offered for frequent attacks that affect quality of life, persistent symptoms, fistulas or narrowing of the colon. It is no longer automatic after two attacks.

Is diverticulitis the same as diverticulosis?

No. Diverticulosis means having pouches in the colon, which is common and usually causes no symptoms. Diverticulitis is when those pouches become inflamed or infected, causing pain and fever.