Diverticular disease: symptoms, causes, diet and treatment

The large bowel is the last part of the digestive tract. Diverticula are small pouches that stick out from its wall. Guts UK explains that they form where the bowel wall becomes weak, which can happen as we get older, and that they are most often found in the lower left part of the bowel.

The words used for the different stages are easy to mix up. The NHS says that most people will get some diverticula as they get older, but most will never have symptoms.

The NHS lists the symptoms of diverticular disease as pain in the lower left side of the tummy (a small number of people get pain on the right), tummy pain that gets worse after you eat and gets better after you poo or fart, constipation, diarrhoea, blood in your poo and bloating. Guts UK adds that the pain may come and go, and that in people of South Asian background the pain is sometimes on the right side instead of the left.

If the bowel becomes infected or inflamed, it is called diverticulitis. The NHS says you may then have severe, constant tummy pain, a high temperature, and bleeding or passing slime (mucus) from your bottom.

Symptoms can look like those of other conditions. The NHS says they are similar to irritable bowel syndrome, and Guts UK also names bowel cancer and colitis. For that reason, it is important not to assume that every bowel problem is diverticular disease, particularly if symptoms are new or change.

Guts UK says doctors are still not exactly sure why diverticula form, but some things make it more likely. Pressure inside the bowel can push the lining outwards through weak places in the wall.

• Age is the biggest risk factor. Guts UK says the chance of developing diverticula increases after the age of 40, and that more people under 45 are now being diagnosed, although this is still uncommon.

• Lifestyle factors can raise the risk of symptoms or complications: a higher than healthy body weight, not being physically active and smoking.

• Rare inherited conditions that weaken the bowel wall, including Ehlers-Danlos syndrome, Marfan syndrome and Williams syndrome, make diverticula more likely.

• Fibre and constipation: Guts UK says some studies suggest more fibre may lower the risk of diverticula but others find no clear link, and it is not proven that constipation causes them.

NICE advises people with diverticulosis or diverticular disease to eat a healthy, balanced diet including whole grains, fruit and vegetables, and to increase fibre gradually if they are not used to it, which may minimise wind and bloating. It adds that benefits of more fibre may take several weeks, and that a high-fibre diet should be maintained for life.

Guts UK suggests a fibre-rich starchy food with each meal, at least 5 portions of fruit and vegetables a day, and at least 2 litres (about 8 to 10 cups) of water or other non-caffeinated drinks. It suggests limiting red and processed meat to no more than 70 grams a day.

Older advice told people to avoid seeds, nuts, popcorn and fruit skins. NICE says there is no need to avoid them, and Guts UK says these foods do not increase the risk of diverticulitis or bleeding. Guts UK also says there is no good evidence that a low-fibre diet speeds recovery from a flare-up of diverticulitis, although people with complications may be given different advice by their doctor or dietitian.

Guts UK does not recommend probiotics for diverticular disease because there is not enough good evidence that they work.

• Do eat whole grains, fruit and vegetables, and increase fibre slowly with plenty of fluids.

• Do stop smoking, keep to a healthy weight and take regular exercise, which NICE says reduce the risk of diverticulitis and symptomatic disease.

• Do not avoid seeds, nuts, popcorn or fruit skins because of diverticular disease.

• Do not take NSAIDs such as ibuprofen or opioid painkillers such as codeine unless a doctor advises it. The NHS says they can cause stomach problems or constipation and increase the risk of a hole (perforation) in the bowel.

For diverticular disease with symptoms, the NHS lists painkillers such as paracetamol, bulk-forming laxatives for constipation and diarrhoea, and medicines to help with stomach cramps (antispasmodics). NICE recommends considering each of these where they fit your symptoms, and says that if symptoms persist or do not respond to treatment, alternative causes should be considered and investigated.

NICE says antibiotics should not be offered to people with diverticular disease. For diverticulitis, the NHS says antibiotics are used if the diverticulitis is caused by an infection, alongside painkillers. NICE says that if a person with acute diverticulitis is systemically well, a no-antibiotic strategy can be considered with paracetamol and advice to come back if symptoms persist or worsen. Antibiotics are offered if the person is systemically unwell, immunosuppressed or has significant other conditions, with co-amoxiclav for 5 days the first-choice oral course for uncomplicated acute diverticulitis.

Guts UK says that for mild symptoms your doctor may suggest a watch-and-wait approach, and that surgery is not usually needed. It may be offered after a serious episode, for example if an abscess forms around the bowel or an infection spreads into the abdomen from a perforated pouch. The operation usually removes the part of the bowel with the damaged pouches, and the surgeon may sometimes need to bring the healthy end of the bowel out through the skin as a stoma, which is often temporary.

The NHS says a GP will ask questions to find out what is causing your symptoms, and you may need a blood test or a poo sample. Further tests to confirm diverticular disease or diverticulitis and rule out other conditions can include a colonoscopy or flexible sigmoidoscopy, in which a thin tube with a small camera checks inside the bowel, or a CT scan.

Guts UK describes CT colonography as a scan that looks more closely at the bowel without putting a camera inside it, and explains that the bowel needs to be emptied with a laxative before a colonoscopy or CT colonography. NICE says people should not routinely be referred for suspected diverticular disease unless tests cannot be organised from primary care, colitis is suspected, or they meet the criteria for a suspected cancer pathway.

Guts UK says very few people have complications severe enough to need hospital admission, and that diverticulitis is the most common complication, occurring in up to a quarter of people with the condition.

The NHS lists rare serious complications: a build-up of pus (abscess), a blockage in the bowel, an opening between the bowel and another organ such as the bladder (a fistula), and a hole (perforation) in the bowel, which can cause a severe infection called peritonitis. These can sometimes be treated with antibiotics or surgery, and some people will need a colostomy.

Bleeding is another complication. Guts UK says a blood vessel in a pouch can burst, that in most people (8 out of 10) the bleeding stops on its own, and that heavy bleeding needs emergency care.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have any of the following. Call 999 or go to A&E if you have severe tummy pain and are vomiting, have a swollen tummy or cannot poo or fart, if you are bleeding heavily from the bottom, or if you are confused, have pale or blotchy skin, a very high or low temperature or are breathless, which could be signs of sepsis.

• There is blood or slime (mucus) in your poo.

• You have tummy pain that is getting worse or does not go away.

• You have a high temperature, or feel hot, cold or shivery.

• You keep being sick and cannot keep fluid down.

• You have diarrhoea for more than 7 days or have been sick for more than 2 days.

On the NHS, diagnosis and day-to-day management usually start with a GP, who can arrange blood and stool tests and, where needed, a colonoscopy, flexible sigmoidoscopy or CT scan. NICE advises same-day hospital assessment if complicated acute diverticulitis is suspected, for example with uncontrolled pain and signs of an abscess, perforation, sepsis or a blocked bowel.

Some people choose private gastroenterology for faster access to a scan or colonoscopy. The tests and the advice on diet, fluids and medicines are the same, so it is reasonable to ask which test is planned and what the result would change. Keep your GP informed so your records stay joined up.