Diverticulosis vs diverticulitis: the difference, symptoms and treatment

The large intestine (colon) is a muscular tube. Over the years, weak spots in its wall can bulge outwards to form small pouches called diverticula. The NHS explains that diverticular disease and diverticulitis are caused by these small bulges or pouches in the walls of the intestine.

Guts UK separates the terms clearly: diverticulosis means you have diverticula in your bowel, and most people with diverticulosis do not have any symptoms and will not need treatment. Diverticulitis happens when one or more diverticular pouches become inflamed or infected. The in-between label, diverticular disease, is used for symptoms attributed to diverticula without acute infection.

The NHS says the symptoms of diverticular disease include pain in the lower left side of the tummy (a small number of people get pain on the right side), pain that gets worse after eating and better after pooing or passing wind, constipation, diarrhoea, blood in the poo and bloating. If the bowel becomes infected or inflamed, called diverticulitis, there may also be severe constant tummy pain, a high temperature, and bleeding or passing slime (mucus) from the bottom.

The NHS points out that the symptoms are similar to those of other conditions such as irritable bowel syndrome, and Guts UK adds bowel cancer and colitis to the list of conditions that can look similar, so it is important not to assume that all tummy problems are caused by diverticular disease.

Age is the biggest risk factor, according to Guts UK, with chances of developing diverticula increasing after the age of 40 and affecting around 1 in 2 people as the population gets older. It says other things that may increase the risk of symptoms or complications include not being physically active and smoking, which is linked to a higher risk of needing hospital care, and that some studies suggest eating more fibre, especially from vegetables, may lower the risk of diverticula. Some inherited connective tissue conditions such as Ehlers-Danlos syndrome and Marfan syndrome can make the bowel wall weaker.

The current theory for inflammation, per Guts UK, is that inflammation and infection occur because of an overgrowth of bacteria in the diverticula. Why one person develops diverticulitis and another does not is not fully understood.

The NHS advises asking for an urgent GP appointment or getting help from NHS 111 if there is blood or slime in your poo, tummy pain that is getting worse or does not go away, a high temperature or feeling hot, cold or shivery, you keep being sick and cannot keep fluid down, or you have diarrhoea for more than 7 days or are being sick for more than 2 days.

It says to call 999 or go to A&E if there is severe tummy pain and the person is vomiting, has a swollen tummy or cannot poo or fart, if there is heavy bleeding from the bottom, or if they are confused, have pale or blotchy skin, a very high or low temperature, or are breathless or breathing rapidly, which could be signs of sepsis.

Diverticulosis is often found incidentally when a colonoscopy, CT scan or other test is done for another reason. The NHS says that for suspected diverticular disease or diverticulitis the GP will ask questions, and you may need a blood test or a poo sample, and further tests such as a colonoscopy or flexible sigmoidoscopy or a CT scan to confirm the diagnosis and rule out other conditions.

Guts UK explains that a colonoscopy looks at the whole bowel, while a sigmoidoscopy looks only at the left side, and that you will need to empty the bowels beforehand with a laxative. Guts UK also says there is no evidence that having diverticular disease, whether or not you have symptoms, increases your risk of bowel cancer, though doctors may still examine the bowel to exclude other conditions.

The NHS says treatments that can help the symptoms of diverticular disease include painkillers such as paracetamol, bulk-forming laxatives for constipation and diarrhoea and medicines to help stomach cramps (antispasmodics). Diverticulitis is treated with antibiotics if it is caused by an infection and with painkillers such as paracetamol.

Guts UK says complicated diverticulitis requiring hospitalisation is normally treated with antibiotics and fluids. Complications include a collection of pus (abscess), which may need a needle to drain, blockage of the bowel, fistulas to organs such as the bladder or vagina, and peritonitis, which nearly always requires emergency surgery. Surgery for abscess, blockage or perforation may include removing an infected part of the bowel, and some people need a colostomy.

The NHS advises eating a healthy, balanced diet including whole grains, fruit and vegetables, noting that there are no specific foods you need to avoid, slowly increasing the amount of fibre you eat if you do not eat much, drinking plenty of water, stopping smoking and maintaining a healthy weight. It advises not taking NSAIDs such as ibuprofen or opioid painkillers such as codeine because they can cause stomach problems or constipation and increase the risk of perforation.

The old advice to avoid nuts, seeds and popcorn is not supported by the NHS statement that there are no specific foods you need to avoid. If you are being treated for an acute attack, follow the advice of the clinician looking after you.

Most people with diverticulosis never have symptoms. Some people have recurrent episodes or ongoing symptoms and are monitored by a GP or specialist. The NHS notes that rarely diverticulitis can lead to serious complications, which may be treated with antibiotics or surgery.

Because symptoms can overlap with other bowel conditions, new or persistent changes in bowel habit, blood in the stool or weight loss should be assessed rather than attributed to diverticula without examination.

On the NHS, a GP assesses symptoms and arranges blood and stool tests. Urgent attacks are managed in hospital, and persistent symptoms or recurrent attacks are referred to gastroenterology or colorectal surgery. Colonoscopy and CT are widely available through NHS endoscopy and radiology departments.

Private gastroenterologists and colorectal surgeons can offer quicker colonoscopy or CT and advice on recurrent diverticulitis. Because decisions about elective surgery are individual, a second opinion can be useful, but acute attacks with severe pain or fever should be managed urgently through NHS emergency services.