Everything you need to know about Diverticulitis

The bowels are an incredibly important organ within the human body and play a key role in our health and wellbeing. The bowels are an organ that is part of the digestive system in the human body. The digestive system is the group of organs that allow us to eat and to use the food we eat to fuel our bodies.

The large bowel, or colon, removes water, salt and some nutrients, forming a stool. The large intestine becomes weaker with age, and the pressure of hard stools passing through the large intestine is thought to cause bulges to form, which are known as diverticula.

Diverticula are small, bulging pouches that can form in the lining of your digestive system. They are found most often in the lower part of the large intestine, the colon. According to the National Institute for Health and Clinical Excellence (NICE), the presence of diverticula in the wall of the colon is known as diverticulosis and is increasingly common with age.

Although present in only 10% of people under 40 years of age in the UK, over 50% of the population aged over 50 years are affected, rising to 70% by 80 years of age. Most people with diverticula do not get any symptoms; when there are no symptoms, it is called diverticulosis. The precise prevalence of diverticulosis is unknown, as most people are asymptomatic. When bacteria become trapped inside one of the bulges it is known as diverticulitis.

What is diverticulitis?

Diverticulitis and diverticular disease are related digestive conditions that affect the large intestine, that is the colon.

Diverticulosis occurs when diverticula pouches begin to protrude outward from the wall of the colon, but there is no infection or symptoms. When bacteria become trapped inside one or more of the diverticula bulges, the condition that describes the infection that occurs is called diverticulitis. It triggers the diverticula bulges to become inflamed and causes more severe symptoms such as lower abdominal pain, fever, general malaise, and occasionally rectal bleeding.

What causes diverticulitis?

The exact cause of the development of diverticular disease and diverticulitis is not known. What is known is that diverticular disease and diverticulitis are caused by the small diverticula bulges in the large intestine developing and becoming inflamed.

The pressure of moving hard, small pieces of stool through your large intestine creates weak spots in the outside layer of muscle. This allows the inner layer, known as the mucosa, to squeeze through these weak spots, creating the diverticula. If any of the diverticula become infected, this leads to symptoms of diverticulitis.

Diverticula are more common amongst people with an unhealthy high body weight. A lifelong diet deficient in fibre is also associated with the development of diverticula, and studies indicate that dietary fibre has a protective effect against the development of diverticulosis and diverticulitis; however, the exact role of diet is unclear. Diverticular disease and diverticulitis are both much more common in Western countries, where many people do not eat enough fibre, so lack of fibre is thought to play a role in the development of the condition.

Risk factors of diverticulitis

Men and women are equally affected by diverticulitis and a person’s genes contribute 40%–50% of diverticulitis risk.

Incidence of diverticulitis increases with age, and it is most common in people aged over 50 – 60 years. It is estimated that 10% of people have diverticula by the time they are 40 years old, and at least 70% of people have them by the time they are 80 years old. About 80 – 85% of people with diverticula remain asymptomatic, about 10 – 15% develop symptomatic diverticular disease, and the remainder develop diverticulitis.

Diets rich in red meat are associated with an increased risk of diverticulitis, and compared with meat-eaters, a vegetarian diet is associated with reduced risk of hospital admission or death due to diverticular disease.

Obesity has been associated with an increased risk of diverticulitis, complications, recurrence and diverticular bleeding.

Smoking has been linked to the development of diverticular disease and diverticulitis, and is associated with an increased risk of complications.

There is a strong association between nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen, opioid analgesic use such as tramadol, methadone, or codeine, and perforation of colonic diverticula. NSAIDs are also associated with diverticular bleeding.

People who are immunosuppressed have an increased risk of acute diverticulitis, complicated diverticulitis, and mortality from diverticulitis compared with people who are immunocompetent.

What are the diverticulitis symptoms?

About 80% of people with the condition are asymptomatic. When present, symptoms can range from intermittent mild abdominal discomfort through to life-threatening problems such as bleeding and perforation.

The signs and symptoms of diverticulitis can include:

• Pain, which may be constant and persist for several days. The lower left side of the abdomen is the usual site of the pain. Sometimes, however, the right side of the abdomen is more painful, especially in people of Asian descent.
• Nausea and vomiting.
• Fever.
• Abdominal tenderness.
• Change in bowel habit, constipation or, less commonly, diarrhoea.
• Bloating, an increase in abdominal size due to gas.
• Mucus or blood in the stool.

The pattern of symptoms differs from one person to the next, but the pain is often cramp-like, and it comes and goes. Some people may get bloating and/or cramp-like pain in the abdomen which can often start after food is eaten and which is eased by going to the toilet.

Anyone experiencing these symptoms, or a change in symptoms or developing new symptoms, especially blood in their stools, should consult their GP immediately.

How is diverticulitis diagnosed?

Because abdominal pain can indicate a number of problems, your doctor will need to rule out other causes of your symptoms. Diagnosis is made by examination of the inside of the large bowel.

During the examination the doctor will be looking for other abnormalities that could be causing your symptoms. Diagnosis is only confirmed once other conditions have been ruled out. Diverticular disease and diverticulitis can be mistaken for Irritable Bowel Syndrome (IBS) because of the similarity of symptoms.

Tests carried out by your GP will help to rule this out. Tests to help to diagnose diverticulitis may include:

• Blood and urine tests, to check for signs of infection.
• A pregnancy test for women of childbearing age, to rule out pregnancy as a cause of abdominal pain.
• A liver enzyme test, to rule out liver-related causes of abdominal pain.
• A stool test, to rule out infection in people who have diarrhoea.
• A barium enema – This is when a liquid is inserted into the intestine through the anus and an X-ray of the abdomen is taken.
• Colonoscopy or sigmoidoscopy – This is where a tube with a camera is passed into the large bowel via the back passage to view the inner surface of the large bowel. A sigmoidoscopy is a similar procedure that views less of the large bowel. Medicine can be given to make the procedure more comfortable. You will be given medicine to make you evacuate your bowel before the procedure, which ensures you completely empty your bowels. This medicine will cause diarrhoea and urgency, so it is a good idea to stay near a toilet.
• CT scan – This is a non-invasive X-ray-based test, although, as with the colonoscopy, you will be required to completely empty your bowels before the scan. The CT scan can identify inflamed or infected pouches and confirm a diagnosis of diverticulitis. A CT can also indicate the severity of diverticulitis and guide treatment.

Complications of diverticulitis

Simple diverticulitis, which accounts for 75% of cases, is not associated with complications and typically responds to medical treatment without surgery. Complicated diverticulitis occurs in 25% of cases and usually requires surgery.

Complications associated with diverticulitis can include the following:

• An abscess – This is a localised collection of pus usually caused by a bacterial infection. An abscess is the most common complication associated with diverticulitis. An abscess is a cavity within body tissue containing pus and surrounded by inflamed tissue and may arise from an infected diverticulum if the infection spreads to the neighbouring tissue. One may also form if a diverticulum perforates and rather than entering the abdominal space, the released diverticular contents become walled off. You may know that you have an abscess if you can feel a tender lump in the abdomen area and you have a persistent fever. Some small abscesses resolve by themselves; those that don’t are treated with continued antibiotics and bowel rest. Larger and persistent abscesses may need to be eliminated by drainage of the pus from the abscess which should reduce the inflammation and associated pain. This will be done in hospital. To drain, a tube will be inserted through the abdominal wall and a CT scan may be used to help locate the abscess. It is important to try and get rid of abscesses because if an abscess bursts it can create a dangerous infection
• A phlegmon – This is similar to an abscess as it contains pus but the pus is found in lots of small pockets that are spread within tissue that becomes a hardened mass of infection and inflammation. A phlegmon may be felt as a tender lump in the abdomen and is also painful. There is a risk that tissues could adhere to a neighbouring piece of intestine. This adhesion could make the intestine kink and become blocked which would lead to vomiting and it could also be painful when food is forced through the narrow intestine. There can also be an irritation caused to the bladder which can lead to a more frequent need to urinate. A phlegmon may have to be removed by surgery if it does not respond to antibiotic treatment.
• A fistula – This is an abnormal tract between two areas that are not normally connected. In relation to diverticulitis, a fistula may develop from any part of the inflamed colon. If a fistula forms, it is usually between the colon and the bladder. The fistula is created in a gradual process in which the surface of the abscess is broken and the leaking pus is quickly enclosed by tissue, forming a protruding tube. The process is repeated many times and the tube containing pus gradually extends until it reaches another hollow organ or the skin surface. On completion of the fistula, the tube remains open releasing pus. If a fistula forms between a colonic abscess and the bladder, then pus or faeces may appear in the urine. This can lead to Urinary Tract Infections. Colon-bladder fistulas are more common in men. Women may, however, develop fistulas from the colon to the vagina, particularly if they have had a hysterectomy. Fistulas may also connect with the small intestine or with the skin surface. To treat a fistula, an operation will be conducted to remove the section of the colon where the fistula has grown. Usually any holes created by the fistula will close on their own but larger holes may need to be sewn in order to close them.
• An obstruction – In very rare cases of diverticulitis, the intestine can become blocked. However, bowel obstruction does not necessarily mean a total blockage; the intestinal tube narrows so that large lumps of faeces cannot pass, but liquid faeces can dribble through. When faeces become blocked, static faeces may encourage an overgrowth of bacteria, which can lead to an infection. A blockage in the large intestine may be caused by inflammation that swells the tissues that surround the colon; this consequently narrows the colonic space. The small intestine can also be affected by an obstruction. This will happen when the small intestine becomes kinked or twisted when incorporated into an inflammatory mass in the area of the sigmoid colon. The symptoms of an obstruction will be abdominal pain, bloating and vomiting. An obstruction is usually treated by following a liquid diet. If there are several obstructions, then surgery may be something that is necessary to remove the affected area or widen the colon.
• Perforation – This is a puncture in the bowel wall. Diverticulum can perforate which will enable some of the contents of the colon into the abdominal space. A perforation is a rare occurrence but when it does happen, it is dangerous as it could cause peritonitis.
• Peritonitis – This is inflammation of the peritoneum which is triggered by its infection by bacteria. The peritoneum is a membrane that lines the whole abdominal space and also the contained organs. If peritonitis does occur, an emergency operation will be required. The main sign to look out for is severe abdominal pain which can develop quickly. Left untreated, it can become life-threatening.
• Sepsis – This is an overwhelming body-wide infection that can lead to the failure of multiple organs. It happens when your immune system overreacts to an infection and starts to damage your body’s own tissues and organs.
• Diverticular haemorrhage – This occurs in about 15% of people with diverticulosis, diverticular disease, or diverticulitis. Diverticular bleeding occurs when a small artery located within a diverticulum is eroded and bleeds into the colon. Diverticular bleeding usually causes painless bleeding from the rectum. In approximately 50% of cases, the person will see maroon or bright red blood with bowel movements. People who have right-sided diverticula have a greater likelihood of haemorrhage.

The risk of complications, such as peritonitis or perforation, is greater during the first episode of diverticulitis, and the risk reduces with each recurrence. Diverticulitis recurs in around one third of people following response to medical treatment (BMJ, 2021), about 50% of recurrences occur within one year of the initial episode, and 90% occur within 5 years.

Recurrence is:

• More common in younger people, in those with an abscess at diagnosis, and after an episode of complicated diverticulitis.
• Associated with high mortality and a less favourable response to therapy.
• More common amongst people who are immunocompromised and who have a five-fold increased risk of recurrence with complications, such as bowel perforation, compared to immunocompetent people.

How to treat diverticulitis

Diverticulitis is usually treated with antibiotics and a liquid diet for a few days while your bowel heals. Once your symptoms improve, you can gradually add solid food to your diet.

In some cases, you may need to be admitted to hospital for intravenous antibiotics. Surgery may be needed to drain an abscess, or if a diverticulum bursts (peritonitis) or causes the bowel to become blocked (obstruction). Sometimes this can be done using X-ray guidance so you can avoid an anaesthetic.

You will be more likely to need surgery to treat diverticulitis if:

• You have a complication, such as those described above.
• You have had multiple episodes of uncomplicated diverticulitis.
• You have a weakened immune system.

Where a severe bleeding episode has occurred an emergency blood transfusion may be required. Bleeding usually stops without treatment in 8 in 10 people who experience a severe bleeding episode. In those who do not stop bleeding, a special X-ray test can be used to identify the site of bleeding and stop it in the majority of cases.

Following surgical treatment, approximately 25% of people remain symptomatic (BMJ, 2021).

Final thoughts

A change in diet often helps in the management of diverticulitis. Generally, a high fibre diet is recommended; however, it is important to increase this gradually and find the best level of fibre for you, as in a few people high fibre intake can make some symptoms worse.

A healthy, balanced diet should include whole grains, fruit and vegetables with the aim of having a fibre-containing starchy food such as wholemeal, brown or granary bread or oat or rye bread with each meal, plus five portions of fruit and/or vegetables per day. Try to drink at least two litres, that is about eight to ten cups of fluid, every day to help the fibre pass through the bowel.

You should also take regular exercise, lose weight if you are overweight or obese, and stop smoking. However, the studies on which these recommendations are made are not highly definite for reducing the risk of developing a complication from diverticulitis. Also, there is no evidence that probiotics – good bacteria – are helpful in treating episodes of diverticulitis.

There are sources of advice and support for anyone suffering from diverticulitis.

These include:

• Bowel Research UK 020 3540 8694.
• Guts UK 020 7486 0341.
• My Diverticulitis.
• Polycystic Kidney Disease Charity Helpline on 0300 111 1234.
• ‘Coping with Diverticulitis’ – book by Peter Cartwright with useful information and advice (external link to Amazon books UK).