Diverticular disease describes conditions associated with diverticula, which are small pouch-like protrusions that form through weak points in the wall of the colon. The presence of these pouches without symptoms is generally called diverticulosis. When diverticula are associated with chronic gastrointestinal symptoms, bleeding, inflammation or other complications, the broader term diverticular disease is used. Diverticula most commonly occur in the sigmoid and lower colon, although they can occur elsewhere.
They become increasingly common with age, and many people with diverticulosis never develop symptoms or complications. The existence of diverticula therefore does not automatically mean that a person has active disease or requires treatment. The terms diverticulosis, diverticular disease and diverticulitis describe related but distinct clinical situations and should not be used interchangeably.
Diverticula form where the colonic wall has areas of relative weakness, particularly around points where blood vessels penetrate the muscular wall. Pressure within the colon and changes in the structure of the bowel wall can contribute to the development of pouches. Age-related changes in connective tissue and intestinal muscle are important, although diverticular disease is multifactorial. Genetic susceptibility, altered connective-tissue properties, intestinal motility, microbiome changes and immune factors are being investigated.
Historically, diverticular disease was often attributed primarily to a low-fibre diet and high intraluminal pressure, but current understanding is more nuanced and recognises that several biological and environmental factors interact. A low-fibre dietary pattern may be associated with risk in some populations, but the formation of diverticula cannot be explained by fibre intake alone. Similarly, the presence of diverticula does not necessarily indicate poor diet or unhealthy behaviour.
Most people with diverticulosis have no symptoms and may discover diverticula incidentally during imaging, colonoscopy or another investigation. When diverticula are associated with chronic symptoms, people may experience lower abdominal pain or cramping, bloating, constipation or diarrhoea. These symptoms can overlap substantially with IBS, so symptoms alone cannot reliably establish that diverticula are responsible.
Diverticular bleeding can occur when a blood vessel adjacent to a diverticulum becomes damaged, potentially causing rectal bleeding that may range from small amounts to substantial haemorrhage. Diverticulitis occurs when diverticula become inflamed and can produce more acute symptoms, usually including abdominal pain, often in the lower left abdomen, as well as fever, chills, nausea or altered bowel habits. Thus, uncomplicated diverticulosis, symptomatic diverticular disease, diverticular bleeding and diverticulitis represent different clinical manifestations of the same anatomical condition.
Diverticulitis is distinct from diverticulosis because it involves acute inflammation of one or more diverticula and surrounding tissue. It can be uncomplicated, where inflammation remains localised, or complicated, where problems such as abscess, perforation, fistula, obstruction or widespread infection develop. Severe cases can produce systemic illness and require hospital treatment. The exact mechanism by which diverticula become inflamed is not completely established.
Proposed mechanisms include bacterial or stool material becoming trapped in a pouch, alterations in the intestinal microbiome, local pressure or mechanical injury and abnormal immune responses. Not everyone with diverticulosis develops diverticulitis; NIDDK notes that fewer than 5% of people with diverticulosis develop diverticulitis in the cited evidence base. Consequently, having diverticula is a risk state rather than a prediction that inflammation will inevitably occur.
Several factors are associated with diverticular disease or diverticulitis risk. Increasing age is strongly associated with diverticula, while obesity, smoking and physical inactivity have been linked with increased risk of diverticular complications. Dietary patterns may also influence risk, with low-fibre diets and higher red-meat consumption implicated in some evidence. Certain medicines, particularly non-steroidal anti-inflammatory drugs and corticosteroids, can increase the risk of complications in susceptible people.
These associations do not mean that any one factor is sufficient to cause diverticulitis, and individual risk is influenced by multiple variables. Earlier advice often focused on avoiding nuts, seeds or popcorn, but modern evidence does not support a blanket requirement to avoid these foods simply because diverticula are present. Prevention generally focuses on overall bowel health and modification of established risk factors rather than rigidly excluding specific foods without a demonstrated individual reason.
Management depends on which manifestation is present. People with asymptomatic diverticulosis generally do not need treatment directed at the pouches themselves. For chronic symptoms attributed to diverticular disease, clinicians may recommend dietary fibre, fibre supplements and other symptom-directed measures, while alternative diagnoses such as IBS should be considered when symptoms overlap. Diverticular bleeding requires medical assessment because gastrointestinal bleeding has multiple possible causes and can occasionally be substantial.
Diverticulitis may sometimes be managed at home when uncomplicated and the person is clinically stable, whereas severe disease, complications or high-risk circumstances can require hospital admission. Antibiotics are not necessary for every uncomplicated episode and are selected according to clinical circumstances. Pain management and temporary dietary modification may be used during an acute episode, followed by gradual return to normal eating as symptoms improve.
Complications are clinically important because diverticular disease can affect both the bowel and general health. A perforated diverticulum can allow intestinal contents to enter the abdominal cavity and cause peritonitis, while an abscess can develop when infection becomes localised. Fistulas may form abnormal connections between the colon and adjacent organs, and scarring can contribute to bowel obstruction. Diverticular bleeding can occasionally cause substantial blood loss and may require hospital-based investigation or treatment.
Recurrent or complicated diverticulitis may lead to consideration of surgical resection of the affected segment of colon. Surgery is not automatically required after a particular number of uncomplicated episodes; decisions are based on severity, complications, recurrence, individual risks and the overall clinical context. The management principle is therefore to distinguish uncomplicated symptoms from complications requiring urgent intervention rather than treating all diverticular disease in the same way.
Diverticular disease is consequently best understood as a spectrum ranging from asymptomatic diverticulosis to symptomatic disease, bleeding and diverticulitis with potentially serious complications. It is a structural condition involving pouches in the colonic wall and should not be confused with IBS, which does not create diverticula, or IBD, which involves immune-mediated intestinal inflammation. Diverticula become increasingly common with age, yet most people with diverticulosis never develop significant problems.
When symptoms occur, careful assessment is important because abdominal pain, bloating, constipation, diarrhoea and rectal bleeding have many possible causes. Current management emphasises appropriate fibre and lifestyle measures, symptom-directed treatment, recognition of acute diverticulitis, avoidance of unnecessary antibiotics in selected uncomplicated cases and prompt investigation of significant bleeding or severe abdominal symptoms.
