Diverticulitis

Diverticulitis is a digestive condition in which small bulging pouches in the wall of the colon, called diverticula, become inflamed or infected. Diverticula themselves are extremely common, particularly with increasing age, and their mere presence — a condition called diverticulosis — rarely causes any symptoms at all. Diverticulitis refers specifically to the inflamed, symptomatic form of the condition, which typically presents with sudden, often severe abdominal pain.

The great majority of diverticulitis cases are uncomplicated and respond well to conservative treatment, but the condition has a real potential to become serious. If a diverticulum ruptures, infection and inflammation can spread beyond the colon, leading to an abscess, generalised infection within the abdominal cavity (peritonitis), or a bowel obstruction — complications that require urgent, and sometimes surgical, treatment.

How Diverticulitis Develops

Diverticula are small pouches that form where the inner lining of the colon pushes through weak spots in the surrounding muscular wall, most commonly in the lower left part of the colon (the sigmoid colon). They tend to form as a result of increased pressure within the colon over time, often related to a low-fibre diet and chronic constipation, which requires more forceful straining to pass stool.

• Diverticulosis: The presence of diverticula without inflammation or symptoms. Very common, particularly from middle age onward, and in itself not a disease requiring treatment.
• Diverticulitis: Occurs when one or more diverticula become inflamed or infected, thought to result from a micro-perforation or blockage of the pouch, allowing bacteria to multiply and trigger inflammation of the surrounding colon wall.

Uncomplicated vs Complicated Diverticulitis

Diverticulitis is classified by severity, which is the single most important factor guiding treatment.

Uncomplicated Diverticulitis

Inflammation in Uncomplicated Diverticulitis is confined to the affected segment of colon, without abscess, perforation, or spread of infection. Accounts for the majority of cases and can often be managed without hospital admission or, in carefully selected patients, even without antibiotics.

Complicated Diverticulitis

Complicated Diverticulitis Inflammation has led to a further problem - an abscess, perforation, generalised peritonitis, a fistula (an abnormal connection between the colon and another organ), or bowel obstruction. Requires hospital-based treatment, and in more severe cases, surgery.

Symptoms of Diverticulitis

The hallmark symptom is sudden, often severe abdominal pain, most commonly in the lower left abdomen — though it can occur elsewhere, particularly in people of Asian descent, in whom right-sided diverticulitis is more frequently seen.

• Sudden and intense abdominal pain, typically in the lower left abdomen
• Fever, sometimes with chills
• Nausea and vomiting
• Constipation, or less commonly diarrhoea
• Bloating and abdominal tenderness
• Blood in the stool or during bowel movements
• Persistent pain that does not settle with simple measures

Causes and Risk Factors of Diverticulitis

Diverticulitis develops when a diverticulum becomes inflamed or infected, but several factors increase the likelihood of both forming diverticula and developing an inflammatory episode:

• Age: Risk rises significantly with age, as the colon wall naturally weakens over time
• A low-fibre diet: Associated with harder stool, increased straining, and higher pressure within the colon
• Obesity
• Lack of physical activity
• Use of tobacco products
• Heavy alcohol consumption
• Certain medications, including regular use of NSAIDs (such as ibuprofen) and, in some studies, opioids and steroids

Complications of Diveticulitis

While most episodes resolve with treatment and no lasting problems, diverticulitis can lead to several complications if the inflamed diverticulum perforates or infection is not controlled:

• Abscess: A localised collection of pus forming next to the inflamed segment of colon, often requiring drainage in addition to antibiotics
• Perforation and peritonitis: If a diverticulum ruptures fully, bowel contents and bacteria can spread into the abdominal cavity, causing widespread infection (peritonitis), which is a surgical emergency
• Fistula: An abnormal connecting channel that can form between the colon and a nearby organ, most often the bladder, following recurrent or complicated episodes
• Bowel obstruction: Repeated inflammation can cause scarring and narrowing (stricture) of the colon, which can partially or fully block the passage of stool
• Recurrent diverticulitis: Some patients experience repeated episodes, which may prompt a discussion about elective surgery to remove the affected segment of colon

Reducing Your Risk of Diverticulitis

• Eat a high-fibre diet: Fruit, vegetables, whole grains, seeds, and beans improve the movement of waste through the colon and reduce the pressure associated with diverticula formation
• Stay well hydrated: Fibre works by absorbing water, so adequate fluid intake is needed for it to be effective in softening stool
• Maintain a healthy weight and stay physically active: Both are associated with a lower risk of diverticulitis
• Limit red meat intake, particularly alongside a low-fibre diet
• Quit smoking and limit alcohol consumption, both of which are linked to increased risk
• Use NSAIDs sparingly where possible, and discuss alternatives with your doctor if you take them regularly
• If you have had diverticulitis before, attend your recommended follow-up colonoscopy and discuss with your doctor whether any further steps are needed to reduce your risk of recurrence

How Diverticulitis is Diagnosed

• Blood Tests: Checks for signs of infection and inflammation, such as a raised white blood cell count, and helps assess overall severity.
• CT Scan: The primary and most accurate test for diagnosing diverticulitis and determining its severity. Confirms inflammation of the diverticula and identifies complications such as an abscess, perforation, or fistula, which directly guides treatment decisions.
• Ultrasound: Can be used, particularly where CT is not readily available or suitable, to assess for inflammation and complications, though it is generally less sensitive than CT for this condition.
• X-ray: May be used in an acute presentation to look for signs of free air in the abdomen, which can indicate a perforation.
• Colonoscopy: Not performed during an acute flare, as the inflamed bowel carries a higher risk of perforation during the procedure. Instead, colonoscopy is typically recommended six to eight weeks after recovery to examine the colon and rectum directly, rule out other conditions such as colorectal cancer, and assess the extent of diverticular disease.