What Is Diverticulosis?

Diverticulosis is the presence of small pouches in the lining of the intestine known as diverticula (Singular: Diverticulum). They normally develop as we age. Most people with diverticulosis will never develop symptoms. 

Diverticula are usually found in the left side of the large intestine or the sigmoid colon (end of the intestine near the rectum). The presence of diverticula can lead to two related conditions known as diverticular disease and diverticulitis.


Although the terms diverticulosis, diverticular disease and diverticulitis sound similar, they are all slightly different. It is easy to get them confused and you may hear them being used interchangeably, even by medical professionals. The definitions are summarised below:1

  • Diverticulosis - The presence of diverticula, often with no symptoms. Most people with diverticula will not know they have them and they will never develop diverticular disease or diverticulitis
  • Diverticular disease (DD) - The presentation of symptoms associated with diverticula, such as pain in the lower abdomen. It may also be referred to as symptomatic diverticulosis and symptomatic uncomplicated diverticular disease (SUDD)
  • Diverticulitis - The inflammation/infection of the diverticula often resulting in more severe symptoms. It may be caused by tears in the diverticula. The majority of cases are acute diverticulitis, also known as uncomplicated diverticulitis. However, it can lead to complicated diverticulitis and result in hospitalisation

This article will explain the causes of diverticulosis and some of the factors that may lead to the development of diverticulosis, diverticular disease and diverticulitis. It will describe the signs and symptoms of each condition. It will also describe complications that may arise from these conditions alongside how the conditions may be diagnosed and managed/treated.

If you think you may be experiencing any of these complications or symptoms such as extreme stomach pain or bleeding you must seek medical advice. 

Causes of diverticulosis

We don’t really know why people develop diverticulosis and why it leads to diverticulitis. However, there are several hypotheses. It is thought that diverticulosis is caused by high pressure in the colon which leads to weak spots forming in the gut lining. This can then allow these grape-sized diverticula to protrude through the colon wall. 

Diverticulosis can be linked to a variety of factors that are described in the ‘Risk factors’ section of this article. The main ones are age, diet and genetics. Diverticulosis becomes more common as we age, particularly after 40 years of age, and this is likely caused by the weakening of the intestine lining. It is also more common in the Western world and this has been attributed to poor diet.2

Signs and symptoms of diverticulosis

Diverticulosis is usually asymptomatic and is often only discovered incidentally during a colonoscopy that is being carried out for an unrelated reason. If diverticulosis develops into diverticular disease you may experience abdominal pain in your lower left side. This may get worse during/after eating. Other possible symptoms include constipation and/or diarrhoea and occasional blood in your motions.

Diverticulitis (inflammation/infection of the diverticula) may result in more constant, severe abdominal pain. This could also be coupled with a fever, nausea or vomiting, diarrhoea and/or constipation and the presence of mucus/blood in your motions or rectal bleeding. 

Severe pain and bleeding require urgent medical treatment. 

Risk factors

Diverticulosis can be linked to a number of risk factors:3

  • Age: The largest risk factor. As you get older, the wall of your intestine naturally becomes weaker making it more likely for diverticula to form; particularly after the age of 40. However, guts UK reports that more people under the age of 45 are now being diagnosed
  • Diet: It is believed not eating enough fibre causes diverticulosis as fibre helps to soften stool and causes less pressure on the intestinal wall. However, researchers have found it difficult to prove a link between dietary fibre and diverticulosis
  • Genetics: Certain genes have been linked to the development of diverticulosis.4 You are more likely to develop diverticula if a close relative has diverticular disease, particularly if they developed it before they were 50. We also know diverticular disease is associated with people who have Ehlers-Danlos Syndrome, Williams Syndrome, and polycystic kidney disease. This is because these diseases can affect the connective tissue in the bowel
  • Lifestyle choices such as lack of physical activity, not drinking enough water, obesity, and smoking
  • Use of painkillers such as nonsteroidal anti-inflammatory drugs (NSAIDs) and steroids
  • Other factors being researched are changes in the microbiome in the intestines and problems with the immune system

Diagnosis of diverticulosis

If you are experiencing any of the symptoms described above you should visit your healthcare provider (GP). Your doctor will want to rule out certain conditions such as irritable bowel syndrome (IBS), coeliac disease or bowel cancer. They may carry out a couple of tests. These could include:

  • Colonoscopy - A thin tube with a camera at its end will be inserted in your back passage and into the bowel. The camera will be used to look for diverticula and any inflammation or infection that would indicate diverticulitis. Before the procedure, you will be given a laxative to clear out your bowels and may be offered painkillers or a sedative. The procedure itself may be uncomfortable but should not be painful
  • CT scan - CT stands for computerised tomography and is a type of X-ray scan. They also may be referred to as a CAT scan. The scan is non-invasive but will require you to take a laxative to empty your bowels beforehand

Management and treatment of diverticulosis

There is no treatment for asymptomatic diverticulosis. However, the NICE guidelines give advice on how diverticulosis and associated conditions should be diagnosed and managed. Diverticulosis is not harmful unless you are experiencing symptoms. 

Increasing your dietary fibre may help prevent diverticulitis, but is unlikely to stop diverticula from forming.2 You should always aim to eat a balanced diet, consume 30g of dietary fibre a day, and maintain an active lifestyle to promote healthy bowel movements and good digestive health. You should also avoid smoking. 

If you are experiencing abdominal pain, paracetamol can be used to ease this.1 Painkillers such as aspirin and ibuprofen should be avoided as they can cause stomach upset. Codeine should also be avoided as it can lead to constipation. A doctor may prescribe a bulk-forming laxative to treat constipation or diarrhoea. They may also recommend eating a low fibre diet whilst you are experiencing symptoms to rest your digestive system. 

Your doctor will likely prescribe antibiotics to treat diverticulitis. They may also prescribe a stronger painkiller. More serious cases of diverticular disease/ diverticulitis may require hospitalisation.


Those with diverticulitis can develop related complications but this is rare. These include:

  • Abscesses - A collection of pus in the diverticula pouches
  • Bowel Obstruction- Caused by narrowing of the bowel due to diverticula. This could be caused by scarring
  • Fistula - An abnormal passageway between different sections of the bowel or the bowel and other organs such as the bladder
  • Peritonitis - Can happen if the infected/inflamed pouches rupture allowing the contents of the intestine to leak into the abdominal cavity
  • Severe bleeding - Diverticular bleeding can happen if a blood vessel in the diverticulum bursts. This is severe if a lot of blood is lost and may require a blood transfusion

These serious complications could necessitate a surgery known as a colectomy to remove the affected area of the intestine. Most often the surgery requires a colostomy to be created where the bowel is redirected through an opening in the stomach. In most cases, this is reversible after the inflammation has been treated.


How common is diverticulosis?

Diverticulosis becomes significantly more common with age. It is thought 5% of those under 40s will develop diverticulosis and this rises to up to 65% in those over 65.2 However, these figures could be higher as often asymptomatic diverticulosis goes undetected. Amongst those diagnosed with diverticulosis, 20% will develop diverticular disease and, of these,15% develop further complications.3 Diverticulosis is thought to be more prevalent in the Western world due to dietary habits.

How can I prevent diverticulosis?

There is no guarantee that you can prevent diverticulosis as factors such as age and genetics are out of our control. But by living a healthy lifestyle: eating a balanced diet, exercising regularly and avoiding smoking, you can reduce the risk of developing diverticular disease and diverticulitis or minimise symptoms/serious complications. 

When should I see a doctor?

You should see a doctor if you have any symptoms described in this article. Your primary healthcare provider (GP) may carry out examinations and blood tests to rule out any other possible causes. They may refer you for further tests to get a diagnosis.  If you are experiencing severe pain or bleeding you should seek urgent medical attention. 


Diverticulosis is the presence of diverticula, small bulges in the wall of the large intestine. They are normal and develop with age. Diverticulosis can lead to diverticular disease, with symptoms such as pain in the lower left side; and/or diverticulitis, which is inflammation/infection of the diverticula and can result in more severe symptoms and complications. 

Diverticulosis has been linked to factors such as age, diet and genetics. We cannot prevent diverticulosis, particularly as we get older or are genetically predisposed to it. Increasing dietary fibre may help prevent the development of diverticular disease and/or diverticulitis. We should aim to maintain good digestive health by eating a balanced diet, staying physically active, avoiding smoking and drinking enough water. 

Diverticulosis by itself is nothing to worry about and you will likely never know you have it but if you think you may have diverticular disease or diverticulitis then seek medical advice. 


  1. Tursi A, Papa A, Danese S. Review article: the pathophysiology and medical management of diverticulosis and diverticular disease of the colon. Aliment Pharmacol Ther [Internet]. 2015 Sep [cited 2023 Apr 21];42(6):664–84. Available from: https://onlinelibrary.wiley.com/doi/10.1111/apt.13322
  2. Delvaux M. Diverticular disease of the colon in europe: epidemiology, impact on citizen health and prevention: diverticular disease of the colon in europe. Alimentary Pharmacology & Therapeutics [Internet]. 2003 Nov [cited 2023 Apr 20];18:71–4. Available from: http://doi.wiley.com/10.1046/j.0953-0673.2003.01720.x
  3. Tursi A. Diverticulosis today: unfashionable and still under-researched. Therap Adv Gastroenterol [Internet]. 2016 Mar [cited 2023 Apr 20];9(2):213–28. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4749857/
  4. Miuelescu A. Colonic diverticulosis. Is there a genetic component? Maedica (Bucur) [Internet]. 2020 Mar [cited 2023 Jun 23];15(1):105–10. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7221275/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Holly Morgan

PhD in Molecular and Cellular Biology, University of Leeds
MNatSci BSc Natural Sciences, University of Leeds

Holly is currently working as a scientist developing biological drugs for the pharmaceutical industry. During her PhD she worked on methods to conjugate molecules to proteins for biopharmaceutical use. Outside of work, she enjoys combining her love of science and writing to produce articles for Klarity’s health library.

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