Diverticulosis is a bowel condition where small pouches of mucosa (diverticula) protrude from the muscular intestinal wall (National Institute for Health and Care Excellence (NICE), 2019). These, have been described, as ‘herniations’ of mucosa and submucosa through the muscularis, along the mesenteric border. This is seen as an area in the bowel wall where blood vessels (vasa recta) penetrate the bowel wall, leading the muscle to be weaker and more vulnerable to developing these pocket-like protrusions (Aydin and Remzi, 2010) (Figure 1).
The presence of one or more sac-like diverticula is termed ‘diverticulosis’. Most people with this condition do not have symptoms, so it is difficult to determine the level of incidence within any population and, as such, it is often diagnosed as an incidental finding on colonoscopy (Hawkins et al, 2020). Diverticulosis was rarely described in the medical literature before the 1900s, but is increasing in prevalence, particularly in western countries. Given that life expectancy has increased over the past 100 years, along with the advent of sophisticated colonic imaging and cancer screening programmes, this is unsurprising (Rustom and Sharara, 2018). It could be surmised that it has been a problem for longer than it has been discussed in the literature – life expectancy in previous centuries was shorter, making it less likely to occur, and if it did occur it was potentially not diagnosed.
Diverticula occur in the sigmoid and descending colon although 15% of diverticula are found in the ascending colon (most commonly in people of Asian origin). In fact, in Asian countries people with right-side diverticulitis outnumber those with left-side diverticulitis and this has been attributed to dietary and genetic factors. Diverticula can appear in the rectum, but patients are usually asymptomatic (Hawkins et al, 2020).
Diverticulosis is more prevalent with age, and it is postulated that those over the age of 65 years have a 65% likelihood of having diverticulosis, with some studies pointing to an incidence of up to 80% in people over the age of 85 years (Hawkins et al, 2020; Bretto et al, 2022). Incidence reported in studies vary, but all agree that by age 80 most people will have the condition. The mechanical features of the colonic wall change with age (Aydin and Remzi, 2010). It is these age-related changes within the colonic wall such as damage and breakdown of collagen and an increase in luminal pressure, that may predispose these herniations to occur (Painter, 1985; Aydin and Remzi, 2010). Although the majority of people with diverticulosis will remain asymptomatic, 15-20% develop diverticular disease and 5% develop complications such as acute diverticulitis (Carabotti et al, 2021; Bretto et al, 2022).
Diverticular disease
Diverticular disease is a condition where diverticula cause symptoms such as altered bowel habit and lower abdominal pain, but without inflammation or infection (Strate and Morris, 2019). See Box 1. It is classified as a ‘western gastrointestinal disease’ with the highest rates occurring in the USA and Europe and with up to 60-70% prevalence in those over the age of 60 years (Strate and Morris, 2019; Talutis and Kuhnen, 2021). The prevalence of symptomatic, uncomplicated diverticular disease could be lower than expected as demonstrated on a colonoscopy-based cohort study (Tursi et al, 2020) because patients' symptoms were attributed to irritable bowel syndrome (diarrhoea-predominant IBS) (IBS-D) rather than diverticular disease. A Swedish population-based study of randomly selected adults, found age as the strongest predictor of diverticulosis. The study showed that many of those found to have uncomplicated diverticular disease were symptomatic – those over age of 60 years were more likely to report IBS with symptoms of abdominal pain, diarrhoea, urgency and passage of mucus than constipation (Box 2) (Järbrink-Sehgal et al, 2016). Up to 20% of those with diverticular disease develop symptoms of abdominal pain, bloating and altered bowel habit (Järbrink-Sehgal et al, 2016). Recent data suggest that there could be a shared genetic predisposition for diverticular disease and cancer, although studies thus far are not conclusive given that lifestyle factors can increase the risk of both (Fedirko et al, 2023).
Box 1.Glossary of terms
- Diverticula: sac-like protrusions of mucosa that occur in the lining of the colon
- Diverticular disease: diverticula cause symptoms such as lower abdominal pain without inflammation or infection
- Diverticulitis: diverticula may become inflamed and can cause infection, leading to lower abdominal pain, pyrexia, malaise: and rectal bleeding
- Uncomplicated diverticulitis refers to diverticular inflammation without symptoms of acute abdomen, signs of perforation, strictures, or abscess formation
- Complicated diverticulitis refers to diverticular inflammation with complication – including abscess, peritonitis, fistula, stricture, obstruction or perforation
Source: National Institute for Health and Care Excellence, 2019
Box 2.Similarities between diverticular disease and irritable bowel syndrome
- Abdominal pain
- Bloating
- Alternating bowel pattern (constipation and diarrhoea)
- Frequency and urgency of defaecation
- Pain relieved by defaecation (not usually the case in diverticular disease)
Source: National Institute for Health and Care Excellence, 2019
Diverticulitis
Diverticulitis is described as inflammation or perforation of the diverticula, typically causing severe low abdominal pain, pyrexia, malaise, diarrhoea or constipation and at times, rectal bleeding or haemorrhage (NICE, 2019). The progression from normal colon to the presence of diverticula to diverticulitis is not understood (Hawkins et al, 2020). Studies thus far have found that approximately 4-15% of patients with diverticulosis progress to developing diverticulitis (Hawkins et al, 2020). It can be further categorised as complicated or uncomplicated (see Box 1). It can be acute or chronic and affect bowel pattern with diarrhoea, constipation or a combination of both. Risk factors are listed in Box 3.
Box 3.Risk factors for diverticulosis and diverticulitis
- Aged over 40 years
- Being overweight
- Eating a low-fibre diet
- Genetics
- Eating a diet high in fat and red meat
- Sedentary lifestyle with less exercise
- Taking non-steroidal anti-inflammatories (NSAIDS), aspirin and steroids
- Smoking
Source: Wilkins et al 2013; Strate and Morris, 2019
Diagnosis
Diagnosis of diverticulitis is confirmed by symptoms, stool tests, blood tests (particularly raised white cell count and inflammatory markers) endoscopy and abdominal computerised tomography (CT) imaging (Tursi, 2019).
Treatment
Treatment of diverticulitis depends on whether the condition is localised or more advanced. Localised disease can be treated with conservative management such as intravenous fluids and antibiotics, although, in some patients, surgery may be required depending on whether the patient has a complication such as an abscess, fistula formation or bowel obstruction (NICE, 2019). Multiple episodes of diverticulitis may also be an indication for surgery. Diverticular disease is progressive for some (Hawkins et al, 2020). Multiple episodes can lead on to the need for emergency surgery – a more precarious situation for patients than elective surgery, which includes pre-optimisation (Lohsiriwat and Jitmungngan, 2019).
The role of fibre
Historically, there has been debate over causative factors and an association with western diets – typically involving less fibre, more processed foods, more red meat and refined sugars. Although the role of fibre has been most widely studied, the studies are not considered to be of high quality (Carabotti et al, 2021). The studies' findings are not generalisable because the populations studied are different. However, from the data studied, a higher intake of fibre was associated with a decreased risk of diverticulitis and hospitalisation due to diverticular disease (Carabotti et al, 2021). It has been stated in the literature that those aged 50-70 years in the general population who eat a high-fibre diet (25 g per day) have a 40% lower chance of admission to hospital (Carabotti et al, 2021). Carabotti et al, 2021 stated that fibre produces the bulk and stool weight that allows the bowel to more easily push stool through. The theory is that if stools are less bulky, the additional peristalsis required can increase intraluminal pressure, leading to an increased likelihood of herniations being produced at weak points in the anatomy of the bowel. However, the evidence for this is weak (Jaung et al, 2017). It should be noted that the protective effects of fibre for the first episode of diverticulitis may not be the same as preventing recurrent episodes (Schultz et al, 2020). Many studies did not distinguish between patients experiencing diverticulitis, symptomatic diverticular disease and diverticular bleeding in relation to fibre intake. There seems to be a protective effect from fruit and cereal fibre but not plant-based fibre such as that derived from vegetables (Carabotti et al, 2021).
Traditionally, patients with diverticular disease were told to avoid nuts, seeds and corn and other sources of insoluble fibre – on the basis that these may obstruct or block diverticula and increase the risk of bleeding or infection. This has now been largely debunked by the Health Professionals Follow-up Study (HPFS), which showed an inverse association between these fibres and diverticulitis (Barroso and Quigley, 2015). Men who ate these foods at least twice a week were less likely to develop diverticulitis even when there were other risk factors such as obesity, smoking and use of non-steroidal anti-inflammatories. The evidence for following a low-fibre diet during an acute episode has little to support it contrary to traditional advice of low-fibre or low-residue diets. However, when one considers the purported pathophysiological similarities of diverticular disease and IBS eating high-fibre foods when a person has IBS-D symptoms of diarrhoea, urgency, and incontinence is not generally advised (NICE, 2017).
IBS and diverticular disease
Diverticular disease and IBS have similar pathophysiological mechanisms (Alamo and Quigley, 2019; Bretto et al, 2022). Symptomatic diverticular disease and IBS can both cause abdominal pain and discomfort (Spiller, 2012). Both are characterised by an erratic bowel pattern of constipation, diarrhoea, or a combination of both (Box 2). Symptomatic diverticular disease does not show a strong predominance in females, whereas IBS does (Spiller, 2012). IBS pain is usually relieved by defaecation whereas the pain from diverticular disease can be constant. Symptomatic diverticular disease may be characterised by more severe and frequent pain and IBS is likely to be more common in those with diverticular disease (Alamo and Quigley, 2019). These conditions can co-exist and acute diverticulitis may lead on to IBS. The dietary advice can be similar – avoiding caffeine, eating no more than three portions of fruit a day and limiting spicy and processed food (NICE, 2017).
Symptomatic diverticular disease patients show pathological abnormalities in the gut whereas cerebral factors such as visceral hypersensitivity are considered indicative of IBS. Both may be related to the gut microbiome and dysbiosis (Bretto et al, 2022). Dysbiosis is associated with dysmotility, altering nerve fibre activation. Probiotics are a potential treatment for both conditions given the ability to modify colonic microbiota and provide an immunomodulatory effect (Bretto et al, 2022). Thus far the understanding of the similarities between the conditions have not led onto definitive guidance of optimal management (Alamo and Quigley, 2019). One study pointed to people with diverticular disease being more prone to IBS-type symptoms as this was defined as ‘post-diverticulitis IBS’ but it has not been accepted as a formal classification (Cohen et al, 2013).
Continence and diverticular disease
Continence relies on a complex interaction between the brain, nervous system and pelvic organs. The passage of semi-formed stool in addition to the correct signalling and an optimally functioning sphincter complex optimises continence (Heitmann et al, 2021). Faecal incontinence is defined as any involuntary loss of solid or liquid stool. In some definitions involuntary loss from the anus also includes mucus and flatus (Saldana Ruiz and Kaiser, 2017; Heitmann et al, 2021). Risk factors for incontinence are age, general illness, rectal urgency and diarrhoea (Bharucha et al, 2022). Given the relationship to harder or loose stools, and age as an added risk factor, it seems logical that continence can be affected by the presence of symptomatic diverticular disease and diverticulitis, which becomes more prevalent in older adults. Prevalence is likely to be increased in symptomatic diverticular disease, where diarrhoea, stool frequency and urgency occur (Järbrink-Sehgal et al, 2016). Furthermore, some patients with diverticular disease who experience constipation can also experience stool leakage due to overflow.
Conclusion
Diverticulosis is common. The exact reason for progression to diverticular disease and diverticulitis is unknown. Diverticular disease may present with similar symptoms to IBS. Fibre may be important in preventing it but there is no definitive evidence it can reduce recurrent episodes. Further well-designed high-quality studies need to be performed to better identify preventive, causative and exacerbating factors, particularly given that it is plausible that there could be a shared genetic predisposition for diverticular disease and cancer (Fedirko et al, 2023). IBS symptoms and age are strong causative factors, but although diverticular disease shares many similar features, there is a dearth of research on its direct impact on continence.