Diverticulitis: Symptoms, Causes, Treatment & Warnings

This guide explains diverticulitis symptoms, causes, treatment and warning signs in clear language. It covers common symptoms, tests, care options, and important warnings.

Diverticulitis often causes lower-left belly pain, fever, nausea, and changes in bowel habits. Other conditions can cause similar belly symptoms.

Constant, unexplained belly pain needs medical review. This is especially important with fever or clear changes in bowel habits.

Diverticula are small pouches that push through weak spots in the colon wall ¹. The colon is also called the large intestine.

One pouch is a diverticulum, while several pouches are diverticula. Diverticulosis means these pouches are present.

Most people with diverticulosis have no symptoms ⁹. Doctors often find the pouches during imaging or a colonoscopy ⁹.

Diverticulitis starts when one or more pouches become inflamed or infected. Inflammation sends more blood, fluid, and immune cells to the area.

Diverticular disease is a broad term for symptoms or problems linked to diverticula ^1,4. These problems may include pain, bleeding, inflammation, infection, or other complications ^1,4.

Doctors divide diverticulitis into uncomplicated and complicated forms. This difference helps guide treatment and follow-up.

Uncomplicated disease causes inflammation without an abscess or spread of infection. An abscess is a pocket of pus.

About 80% of people with diverticulitis have uncomplicated disease. About 20% have complicated disease.

Complicated disease may cause an abscess, perforation, fistula, blockage, or peritonitis ^2,4. A perforation is a tear in the bowel wall.

A fistula is an abnormal path between the bowel and another organ. Peritonitis means the lining around belly organs becomes inflamed.

Inflammation can cause strong pain and other signs of illness. It may also cause the colon wall to become thicker.

CT scans may show a thick colon wall and inflamed fat near the colon. Free air, an abscess, or a fistula can point to complicated disease.

Pain from acute diverticulitis may start fast or grow worse over time. The pain site and other signs can vary ^3,7.

Lower-left belly pain is the most common symptom. It occurs in about 70% of people with acute diverticulitis.

Pain may start suddenly and feel strong. It may also begin mildly and become worse over time.

Some people have pain that changes in strength during the episode. The belly may also hurt when touched.

An exam may show swelling, guarding, or wider tenderness ^4,6. Guarding is an involuntary tightening of the belly muscles.

Left-sided pain may reach the middle or right side of the lower belly ³. Doctors use exams and tests to diagnose diverticular disease ^4,10.

Some people with acute diverticulitis have a more severe presentation ^3,7:

Blood tests may show more white blood cells or a raised inflammation marker. C-reactive protein is one marker that doctors may check.

Doctors review these results with the exam and imaging findings ^6,10. Symptoms alone cannot show whether the disease is complicated.

Inflammation near the bladder may cause pain during urination ³. It may also cause a more frequent need to urinate ³.

For related guidance, read our UTI symptoms and treatment guide.

Pneumaturia can raise suspicion of a fistula ³. Fecaluria can raise suspicion of a fistula ³.

Either sign should raise concern for a fistula ³. A fistula can be a complication of diverticulitis ^3,7.

Rectal bleeding can occur with diverticular disease ⁹. Diverticular bleeding can happen when a blood vessel near a pouch breaks ¹⁰.

The exact process behind diverticulitis remains unclear ³. Several factors can influence surgical decisions ^3,6.

An older theory linked a blocked pouch with bacteria, pressure, and tiny wall tears ^3,6. Research has challenged a related theory linking nuts, corn, and popcorn to diverticulitis ^3,6.

Tissue damage or bacterial illness may start inflammation inside a pouch. Genes and gut microbes may also play a role ^3,10.

No single process explains every case ^3,10. Research into the cause of diverticulitis continues ³.

Research links several factors with a higher risk of diverticulitis ^7,10:

Researchers have not identified a single gene responsible for recurrent diverticulitis ³. The exact cause still remains uncertain ³.

Studies found no increased risk from nuts, seeds, corn, or popcorn ^3,7,10. These foods do not need routine avoidance for diverticulitis prevention.

Past advice often told people to avoid these foods. Research has not settled all dietary questions in diverticular disease ^3,7,10.

Some nuts and seeds also provide dietary fiber. Personal food choices can follow advice from a doctor or dietitian.

Get medical care for constant, unexplained belly pain. This matters more when pain comes with fever or major stool changes.

Several diverticulitis warning signs need fast medical review. If severe pain occurs with fever, nausea, or a hard belly, see a doctor promptly.

Outpatient care applies to selected people who can drink fluids ⁸. They also need suitable support outside the hospital ⁸.

Air or stool in urine can point to a fistula ³. A clinician should consider a fistula when either sign is reported ³.

Rectal bleeding is another feature that doctors assess ⁹. Diverticular bleeding may require consultation with a gastroenterologist or surgeon for endoscopy ¹⁰.

Complicated diverticulitis may cause widespread pain, swelling, or guarding. It may also cause signs linked with inflammation across the belly.

An abscess, perforation, fistula, or blockage marks complicated disease ^2,4,6. These problems need closer medical care than mild uncomplicated disease ^3,5,6.

Doctors may consider surgery when medical treatment or abscess drainage fails ^3,6. CT imaging can help classify the severity of diverticulitis complications ^3,6.

Doctors begin with a health history and physical exam ¹. They may ask about pain, bowel habits, medicines, and past symptoms ⁹.

Blood tests can show a raised white blood cell count. They can also show increased C-reactive protein.

CT of the abdomen and pelvis is the preferred scan for acute diverticulitis ^4,6. Contrast CT is useful when the diagnosis remains uncertain ⁸.

A CT scan can show colon inflammation, an abscess, free air, or a fistula. It can also help identify a bowel blockage ⁸.

Ultrasound may be considered when CT is not available ⁸. The chosen test can depend on the clinical setting ⁸.

Doctors generally avoid colonoscopy during an acute attack. Performing it during the attack can increase the risk of a bowel perforation.

Diverticulitis treatment depends on the disease type and risk of complications ^1,3. Uncomplicated and complicated cases require different care plans.

Many people with uncomplicated disease can receive outpatient care ⁸. Medical supervision and suitable home support remain important ⁸.

Outpatient care may fit people who can drink fluids and prefer to avoid admission ⁸. Supportive care may include fluids and temporary bowel rest ⁸.

Clinicians may use acetaminophen for pain instead of an NSAID. Medicine choices should follow advice from the treating clinician.

Antibiotics are not routine for every mild uncomplicated case. Some mild cases can improve without them ^3,6.

This approach was studied in selected patients with mild disease ³. Most study patients also had few other illnesses ³.

Studies found similar complication and surgery rates with or without antibiotics ⁸. However, this finding applies to low-risk uncomplicated disease ⁸.

Antibiotics may slightly reduce ongoing disease or short-term recurrence ⁸. A clinician should decide whether antibiotics can be safely skipped ^3,8.

Close follow-up is important during the first few days. These checks help doctors spot signs of complications.

Complicated disease needs antibiotics ^5,8. People at higher risk also need them.

People with weak immune systems need antibiotics, even for uncomplicated disease ³. In some patients, symptoms may be less apparent even as the disease follows a more severe course ³.

The need for a hospital stay may depend on how severe the diverticulitis is. Close medical checks are important for this group ³.

Doctors also weigh scan findings, symptoms, exam results, and other health issues ^3,6. Care should match the needs of each case ^3,6.

Complicated disease is treated in a hospital with antibiotics. Hospital care may also include bowel rest ^3,6.

Fluids may be given to maintain hydration. Antibiotics have traditionally been used for acute diverticulitis ^3,5.

Some abscesses need drainage through the skin. Other severe cases may require surgery.

Reasons for surgery may include perforation, peritonitis, blockage, or severe spread of infection ^3,6. Doctors may remove the affected part of the colon during surgery ¹.

Hospital teams watch the person’s progress closely ³. Worsening signs or poor improvement may lead to another scan ^3,6.

Doctors offer different diet advice during acute diverticulitis. Some advise normal food or easy-to-digest meals.

Others suggest soups, liquids, or low-fiber foods for a short time. Drinking enough fluid is also part of some care plans.

Research has not shown whether avoiding solid food improves recovery. Follow the diet plan provided by the treating care team.

After recovery, doctors may suggest more fiber-rich foods ¹. Good sources include fruits, vegetables, whole grains, beans, nuts, and seeds ^1,7.

Adequate fluids help fiber support stool movement and prevent constipation. Fiber should form part of a wider bowel health plan ^1,7.

Regular exercise may help lower the risk of diverticulitis. Weight management and stopping smoking may also support prevention.

Cutting back on red meat and sweets may help. A clinician or dietitian can help set suitable goals.

Ask a clinician before using ibuprofen, naproxen, diclofenac, or another NSAID. These drugs can raise the chance of complications.

Possible NSAID-related problems include a bowel perforation. Steroids and opioids are also linked with higher risk ^7,10.

Diverticulitis can return after successful treatment. The chance of return is greater after complicated disease.

Repeated attacks do not always lead to surgery. Doctors tailor diverticulitis treatment to each case ^3,6.

The choice of procedure after colon resection is not based on a single factor ^3,6. Doctors also review complications and other health risks ^3,6.

Many uncomplicated cases improve without antibiotics. About 95 out of 100 uncomplicated cases improve within one week.

A scan should first show no abscess before antibiotics are skipped. This approach requires medical checks during the first few days.

It is best suited to selected people with mild disease ^3,6. These people should have working immune systems and few other health issues ³.

Complicated disease and higher-risk cases need antibiotics ^5,8. A clinician should decide whether antibiotics are needed ^3,8.

Uncomplicated diverticulitis often improves within one week. About 5 out of 100 people have symptoms that last longer.

Complicated disease may take longer to settle. In about 80 of 100 cases, it clears within weeks of antibiotic care.

Symptoms that raise suspicion for a fistula need medical assessment ^3,6. Doctors may repeat CT imaging when symptoms do not improve.

Regular checks are especially important during the first few days. They help the care team spot a change in the illness.

Acute diverticulitis can return after a treated episode. The risk is greater after complicated diverticulitis.

A repeat attack does not always mean surgery is needed. Current practice supports a case-by-case choice ^3,6.

Doctors may consider immune status when choosing diverticulitis care ^3,6. Planned surgery should match the needs of that person.

Knowing diverticulitis symptoms, causes, treatment and warning signs can support timely care. Common signs include lower-left pain, fever, nausea, tenderness, constipation, or diarrhea ^3,7.

The exact cause remains uncertain ³. Nuts, seeds, corn, and popcorn have not been shown to raise the risk ^3,7,10.

Get medical care for constant, unexplained belly pain. If severe pain occurs with fever, nausea, or a hard belly, see a doctor promptly. If the belly becomes rigid or pain is severe and rapidly worsening, with high fever, repeated vomiting, or faintness, seek emergency care immediately rather than waiting for a routine appointment.

CT is the preferred scan when confirmation or complication checks are needed ^4,6,8. Mild cases may not need antibiotics, but a clinician must guide that choice ^3,6,8.

Complicated disease needs antibiotics and closer care ^5,8. Some people may also need hospital care, abscess drainage, or surgery.