Diverticular Disease

Diverticular disease refers to a common digestive condition where small pouches develop in the wall of the large intestine. These pouches, called diverticula, form when weak spots in the bowel lining bulge outward under pressure. When multiple pouches are present, the condition is known as diverticulosis, and when these pouches become inflamed or infected, the term diverticulitis is used to describe the condition.

Who Develops This Condition?

This digestive condition becomes increasingly common as we age. While rare in people under 35 years, diverticulosis affects approximately one in three Australians over 45 years of age. By age 85, around two-thirds of people have developed diverticula. Many individuals remain completely unaware they have the condition, as symptoms often never appear.

What Causes Diverticula to Form?

The exact mechanism behind diverticular disease remains is unknown, though several contributing factors have been identified. A diet lacking sufficient fibre appears to play the central role. When dietary fibre intake is low, the stool becomes harder and more difficult to pass. The bowel must generate greater pressure to move this harder stool along, which over time can cause the bowel wall to thicken and develop weak spots that balloon outward.

Research has shown that people who maintain diets rich in fibre are significantly less likely to develop diverticular disease. Beyond dietary factors (such as consuming large amounts of red meat or fatty foods), smoking, excessive alcohol intake, and carrying excess weight all increase the likelihood of developing diverticula. Genetic factors may also contribute, particularly in families where the condition appears across multiple generations.

Diverticula most commonly develop in the sigmoid colon, which sits on the left side of the large bowel. However, in people with inherited forms of the condition, the pouches tend to form on the right side instead. Whilst diverticula can occasionally develop in the small intestine, this occurs much less frequently.

Recognising the Symptoms

Diverticulosis Without Inflammation

Most people with diverticulosis experience no symptoms whatsoever. When symptoms do occur, they tend to be mild and may include crampy discomfort in the abdomen, a sensation of bloating, or changes in bowel habits such as constipation or diarrhoea. These symptoms can overlap with other bowel conditions, including irritable bowel syndrome and bowel cancer, which is why proper medical assessment is important.

When Diverticula Become Inflamed

The hallmark symptom of Diverticulitis is persistent pain in the lower left side of the abdomen. This pain often arrives alongside fever, nausea, vomiting, or loss of appetite. Bowel habits may change noticeably, with some people experiencing constipation whilst others develop diarrhoea. These symptoms usually resolve once the infection and inflammation settle with appropriate treatment.

The encouraging news is that most people experience only a single episode of diverticulitis during their lifetime. Approximately one in seven people who have one attack will experience another. However, for those who do have recurrent episodes, the likelihood of further attacks increases significantly.

How Is Diverticular Disease Diagnosed?

Diverticula may be discovered incidentally during a colonoscopy or on imaging studies such as CT scans performed for other reasons. When diverticulitis is suspected, a CT scan during the acute episode typically confirms the diagnosis and can identify any complications. Blood tests often show abnormalities during an attack, with elevated white blood cell counts or raised inflammatory markers such as C-reactive protein.

Potential Complications

Whilst most episodes of diverticulitis resolve without incident, serious complications can occasionally develop. An abscess, which is a collection of pus, may form within the abdomen. In severe cases, a perforation or hole can develop in the bowel wall, allowing infection to spread into the abdominal cavity—a condition called peritonitis that requires urgent medical attention.

Some people experience severe bleeding from the bowel, usually without pain. The affected segment of bowel may narrow, potentially causing a blockage. Rarely, an abnormal channel called a fistula can form between the bowel and nearby organs such as the bladder.

Treatment Approaches

Managing Uncomplicated Episodes

Treatment focuses on resolving the infection and inflammation, managing pain, and preventing complications. Many episodes of uncomplicated diverticulitis settle within several days without requiring antibiotics. Your doctor may recommend rest, pain relief with paracetamol, and temporarily switching to a low-fibre or fluid-only diet to allow the inflamed bowel to rest.

Antibiotics may be prescribed if symptoms persist beyond three days, if you have a weakened immune system, or if symptoms are more severe. The antibiotics can usually be taken by mouth at home.

When Hospital Treatment Is Needed

More severe cases of diverticulitis, or those involving complications, typically require hospital admission. Treatment in hospital often involves antibiotics and fluids delivered intravenously (i.e. directly into a vein), along with stronger pain relief medication. Most patients respond well to this approach and can return home once symptoms improve.

Surgical Treatment

A small proportion of people with complicated diverticulitis require surgery to remove the diseased section of bowel. Surgery may also be recommended for people who experience repeated attacks or develop other complications of diverticular disease. Emergency surgery is occasionally necessary for severe complications.

Some patients require a temporary stoma, where the bowel is brought to the surface of the abdomen so that bowel contents drain into an external bag. This allows the affected bowel segment to heal properly. In most cases, the stoma can be reversed after a period of healing, and the bowel reconnected. Many Australian hospitals now offer keyhole surgery techniques that can speed recovery and reduce post-operative discomfort.

Following surgery, bowel function and general health typically return to normal, and recurrent problems with diverticular disease become uncommon.

Preventing Diverticulitis

A high-fibre diet containing at least 30 grams of fibre daily helps keep stools soft and may prevent both the formation of new diverticula and inflammation of existing ones. Building fibre intake means including generous serves of fibrous fruits like apples and pears, vegetables, and wholegrain cereals. Baked beans and legumes such as lentils provide excellent fibre sources. Contrary to outdated advice, there is no evidence that nuts, seeds, or corn trigger diverticular disease flares, so these can be enjoyed as part of a balanced high-fibre diet.

Fibre supplements or unprocessed wheat bran can provide an additional four to six grams of fibre daily if dietary sources fall short. Drinking eight cups of water throughout the day and engaging in regular physical activity both support healthy bowel function.

Maintaining a healthy weight is important, as obesity increases the risk of both diverticulitis and diverticular bleeding. Smoking also raises the risk of diverticulitis and its complications, making smoking cessation particularly valuable for people with diverticular disease. The combination of weight management, dietary improvement, smoking cessation, and regular exercise provides the best foundation for preventing future problems.

Key Points to Remember

Diverticular disease affects many Australians, particularly as we age. Most people with diverticulosis never experience symptoms or complications. When diverticula become inflamed, causing diverticulitis, typical symptoms include abdominal pain, fever, nausea, and changes in bowel habits.

Mild episodes often respond to rest and dietary modification without requiring antibiotics. Severe cases may need hospital treatment with intravenous antibiotics and fluids. Whilst serious complications can occur, requiring emergency surgery in some cases, most people recover completely with appropriate treatment.

Maintaining a high-fibre diet, staying well hydrated, exercising regularly, avoiding smoking, and managing weight all help prevent diverticulitis and its complications. If you experience persistent abdominal pain, fever, or significant changes in your bowel habits, seek medical assessment promptly.

This information has been adapted from patient education resources developed by the Gastroenterological Society of Australia (GESA).

Last reviewed: 5 December 2025