INTRODUCTION — Diverticular disease of the colon is an important cause of hospital admissions and a significant contributor to healthcare costs in Western and industrialized societies [1,2].
This topic will review the epidemiology, risk factors, and the pathogenesis of diverticulosis and diverticular disease. The clinical manifestations, diagnosis, and treatment of diverticulitis, diverticular bleeding, and segmental colitis associated with diverticula (diverticular colitis) are discussed in detail, separately. (See "Clinical manifestations and diagnosis of acute diverticulitis in adults" and "Acute colonic diverticulitis: Medical management" and "Colonic diverticular bleeding".)
DEFINITIONS
●A diverticulum is a sac-like protrusion of the colonic wall.
●Diverticulosis is defined by the presence of diverticula. Diverticulosis may be asymptomatic or symptomatic.
●Diverticular disease is defined as clinically significant and symptomatic diverticulosis due to diverticular bleeding, diverticulitis, segmental colitis associated with diverticula, or symptomatic uncomplicated diverticular disease.
•Diverticular bleeding is characterized by painless hematochezia due to segmental weakness of the vasa recta associated with a diverticulum. (See "Colonic diverticular bleeding".)
•Diverticulitis is defined as inflammation of a diverticulum. Diverticulitis may be acute or chronic, uncomplicated or complicated by a diverticular abscess, fistula, bowel obstruction, or free perforation. (See "Clinical manifestations and diagnosis of acute diverticulitis in adults" and "Acute colonic diverticulitis: Medical management".)
•Segmental colitis associated with diverticula or diverticular colitis is characterized by inflammation in the interdiverticular mucosa without involvement of the diverticular orifices. (See "Segmental colitis associated with diverticulosis".)
•Symptomatic uncomplicated diverticular disease is characterized by persistent abdominal pain attributed to diverticula in the absence of macroscopically overt colitis or diverticulitis. This has also been described as smouldering diverticulitis, especially when wall thickening is present in the absence of inflammatory changes on computed tomography.
EPIDEMIOLOGY
●Diverticulosis – The prevalence of diverticulosis is age-dependent, increasing from less than 20 percent at age 40 to 60 percent by age 60 [3,4]. The distribution of diverticulosis within the colon varies by geography:
•Western and industrialized nations have prevalence rates of 5 to 45 percent, depending upon the method of diagnosis and age of the population [5,6]. Approximately 95 percent of patients with diverticula have sigmoid diverticula (image 1) [7]. Diverticula are limited to the sigmoid colon in 65 percent of patients; in 24 percent of patients diverticula predominantly involve the sigmoid, but are also present in other parts of the colon (image 2); in 7 percent of patients diverticula are equally distributed throughout the colon; and in 4 percent diverticula are limited to a segment proximal to the sigmoid colon. The distribution of diverticula may also vary by race. In one prospective study of 624 individuals undergoing screening colonoscopy in the United States, 260 (42 percent) had colonic diverticulosis [8]. While most diverticula in both Black patients and White patients were located in the sigmoid colon, the distribution of the diverticula in the ascending colon or hepatic flexure was higher in Black patients as compared with White patients (20 versus 8 percent).
•In Asia, the prevalence of diverticulosis is between 13 and 25 percent, and diverticulosis is predominantly right-sided [9-13].
•The prevalence of diverticulosis has increased both in the Western hemisphere and in countries that have adopted a more Western lifestyle. As an example, Japan has experienced an increase in the prevalence of right-sided diverticulosis similar to the increase in left-sided diverticula in westernized countries [14,15].
●Diverticular bleeding – Among patients with diverticulosis, bleeding occurs in approximately 5 to 15 percent and is massive in a third of those patients [16]. The right colon is the source of colonic diverticular bleeding in 50 to 90 percent of patients [17-20]. A possible explanation for this is that right-sided diverticula have wider necks and domes, exposing a greater length of vasa recta to injury. Another contributing factor may be the thinner wall of the right colon [16].
●Diverticulitis – Approximately 4 to 15 percent of patients with diverticulosis develop diverticulitis [7,21-23]. The incidence of diverticulitis increases with age. The mean age at admission for acute diverticulitis is 63 years [24]. While the incidence of acute diverticulitis is lower in younger individuals, approximately 16 percent of admissions for acute diverticulitis are in patients under 45 years of age [25]. In contrast to Asia, diverticular disease is predominantly left-sided in western countries, with right-sided diverticulitis being present in only 1.5 percent of cases [26].
The incidence of diverticulitis is increasing. A nationwide inpatient study of hospitalizations in the United States showed an increase in admissions for acute diverticulitis by 26 percent from 1998 to 2005 [24]. The largest increase was in patients aged 18 to 44 years (82 percent). Elective operations for diverticulitis also increased by 29 percent with the largest increase in patients aged 18 to 44 years (73 percent).
Although a male preponderance was noted in early series, subsequent studies have suggested either equal distribution or a female preponderance [7]. Under age 50 years, diverticulitis is more common in men; there is a slight female preponderance between the ages of 50 and 70, and a marked female preponderance over age 70 [27-30].
The prevalence of segmental colitis associated with diverticulosis (diverticular colitis) and symptomatic uncomplicated diverticular disease (SUDD) are unknown.
RISK FACTORS — Several lifestyle factors have been associated with diverticular disease. A prospective cohort study evaluated the association between lifestyle factors and the risk of diverticulitis in over 51,000 men aged 40 to 75 years [31]. There were 907 incident cases of diverticulitis over 757,791 person-years of follow-up. High dietary intake of red meat, low dietary fiber, lack of vigorous physical activity, high BMI (≥25 kg/m2), and smoking (≥40 pack-years) were all independently associated with an increased risk of diverticulitis. There was an incremental reduction in the risk of diverticulitis with an increase in the number of low-risk lifestyle factors (low red meat intake, high dietary fiber, normal BMI, vigorous physical activity, and never-smoker). Adherence to a low-risk lifestyle was associated with a 50 percent (95% CI 20-71) lower risk of diverticulitis.
Diet
Low fiber, high fat, and red meat — Low dietary fiber and high intake of fat or red meat are associated with an increased risk of symptomatic diverticular disease. Dietary fiber and a vegetarian diet may reduce the incidence of symptomatic diverticular disease by decreasing intestinal inflammation and altering the intestinal microbiota [4,32,33]. In a cohort study that included over 47,000 men, after adjustment for age, energy-adjusted total fat intake, and physical activity, total dietary fiber intake was noted to be inversely associated with the risk of symptomatic diverticular disease (RR 0.58 highest quintile versus lowest quintile for fiber intake) [32]. The risk of diverticular disease was significantly increased with diets that were low in fiber and were high in total fat or red meat as compared with diets that were low in both fiber and total fat or red meat (RR 2.35 and 3.32, respectively) [32]. (See 'Definitions' above.)
However, the role of fiber in the development of diverticulosis is unclear. Several early studies suggested that low dietary fiber predisposes to the development of diverticular disease, but other studies have been conflicting [3,32,34-42]. Fiber also does not reduce symptoms in patients with symptomatic uncomplicated diverticular disease [40,41,43,44].
Seeds and nuts — Nut, corn, and popcorn consumption are not associated with an increase in risk of diverticulosis, diverticulitis or diverticular bleeding. In a large observational study that included 47,228 men between the ages of 40 and 75 years, there was an inverse association between the amount of nut and popcorn consumption and the risk of diverticulitis (HR nuts 0.8, 95% CI 0.63-1.01; HR popcorn 0.72, 95% CI 0.56-0.92) [45]. In addition, no association was found between consumption of corn and diverticulitis or between nut, popcorn, or corn consumption and diverticular bleeding or uncomplicated diverticulosis. (See "Acute colonic diverticulitis: Medical management", section on 'Recurrent diverticulitis'.)
Physical inactivity — Vigorous physical activity appears to reduce the risk of diverticulitis and diverticular bleeding. In a prospective study of approximately 48,000 men aged 40 to 75 who were free of known colonic disease at baseline, the risk of developing symptomatic diverticular disease was inversely related to overall physical activity (RR 0.63 for highest versus lowest extremes) after adjustment for age and dietary fat and fiber [46]. Most of the decrease in risk with exercise was associated with vigorous activity such as jogging and running. Men in the lowest quintile for both dietary fiber and physical activity had an increased risk of symptomatic diverticular disease as compared with men in the highest quintile for both (RR 2.56, 95% CI 1.36-4.82).
Obesity — Obesity has been associated with an increase in risk of both diverticulitis and diverticular bleeding. In a large, prospective cohort study of 47,228 male health professionals, there were 801 incident cases of diverticulitis and 383 cases of diverticular bleeding during 18 years of follow-up [47]. The risk of diverticulitis and diverticular bleeding was significantly higher in those with the highest quintile of waist circumference as compared with the lowest (RR diverticulitis 1.56, 95% CI 1.18-2.07; RR diverticular bleeding 1.96, 95% CI 1.30-2.97).
Other — Current smokers appear to be at increased risk for perforated diverticulitis and a diverticular abscess as compared with nonsmokers (OR 1.89, 95% CI 1.15-3.10) [48]. Caffeine and alcohol are not associated with an increased risk for symptomatic diverticular disease [49].
Several medications are associated with an increased risk of diverticulitis and diverticular bleeding including nonsteroidal antiinflammatory drugs, steroids, and opiates [50-53]. In contrast, statins may be associated with a decreased risk of diverticular perforation (OR 0.44, 95% CI 0.20-0.95). In addition, higher levels of vitamin D have been associated with a reduced risk of hospitalization for diverticulitis [54]. In a study that included 9226 patients with uncomplicated diverticulosis and 922 patients with diverticulitis requiring hospitalization, patients with uncomplicated diverticulosis had significantly higher prediagnostic serum levels of 25-hydroxyvitamin D (25(OH)D) levels as compared with patients with diverticulitis requiring hospitalization (29.1 versus 25.3 ng/mL). The risk of hospitalization for diverticulitis decreased with increasing vitamin D levels (adjusted RR highest versus lowest quintile of 25(OH)D 0.49, 95% CI 0.38-0.62).
Patients with Ehler-Danlos, Marfan's, and Williams-Beuren syndromes, HIV infection and those undergoing chemotherapy are also at increased risk for developing acute diverticulitis [30,55-58].
PATHOGENESIS
Diverticulosis — Diverticula develop at well-defined points of weakness, which correspond to where the vasa recta penetrate the circular muscle layer of the colon (figure 1) [18]. A typical colonic diverticulum is a "false" or pulsion diverticulum, in which mucosa and submucosa herniate through the muscle layer, covered only by serosa (picture 1).
Abnormal colonic motility is an important predisposing factor in the development diverticula. Patients with diverticulosis have exaggerated segmentation contractions in which segmental muscular contractions separate the lumen into chambers (image 3). It is hypothesized that the increase in intraluminal pressure predisposes to herniation of mucosa and submucosa. The neural basis for the abnormal motility observed in patients with diverticulosis remains unclear, although one report found that a central event appeared to be upregulation of smooth muscle M3 receptors [59,60].
The development of diverticula specifically in the sigmoid colon can be explained by Laplace’s law according to which pressure (P) is proportional to wall tension (T) and inversely proportional to bowel radius (R), where k is a conversion factor (P = kT ÷ R). Since the sigmoid colon is the segment of the colon with the smallest diameter, it is the site of the highest pressure during segmentation of the colon [61]. Additional structural changes may also decrease resistance of the wall to intraluminal pressure. As an example, most patients with sigmoid diverticula exhibit thickening of the circular muscle layer, shortening of the taeniae, and luminal narrowing. There is no hypertrophy or hyperplasia of the bowel wall, but increased elastin deposition is found in the taeniae [62]. There are also structural changes in collagen that are similar to, but greater in magnitude than those that occur because of aging [63]. Structural changes in the wall may also be responsible for the appearance of diverticula at an early age in connective tissue disorders such as Ehlers-Danlos and Marfan's syndromes and in autosomal dominant polycystic kidney disease [64]. (See "Clinical manifestations and diagnosis of Ehlers-Danlos syndromes" and "Genetics, clinical features, and diagnosis of Marfan syndrome and related disorders" and "Autosomal dominant polycystic kidney disease (ADPKD): Extrarenal manifestations".)
Diverticular bleeding — As a diverticulum herniates, the penetrating vessel responsible for the wall weakness at that point becomes draped over the dome of the diverticulum, separated from the bowel lumen only by mucosa (picture 2) [18]. Over time, the vasa recta is exposed to injury along its luminal aspect, leading to eccentric intimal thickening and thinning of the media. These changes may result in segmental weakness of the artery, predisposing to rupture into the lumen. Diverticular bleeding typically occurs in the absence of diverticulitis [18]. (See "Colonic diverticular bleeding", section on 'Clinical manifestations'.)
Diverticulitis — The underlying cause of diverticulitis is micro- or macroscopic perforation of a diverticulum. It was previously believed that obstruction of diverticula (eg, by fecaliths) increased diverticular pressure and caused perforation. However, such obstruction is now thought to be rare (picture 3 and picture 1) [36]. The primary process is thought to be erosion of the diverticular wall by increased intraluminal pressure or inspissated food particles. Inflammation and focal necrosis ensue, resulting in perforation. (See "Clinical manifestations and diagnosis of acute diverticulitis in adults" and "Acute colonic diverticulitis: Medical management".)
The inflammation is frequently mild, and a small perforation is walled off by pericolic fat and mesentery. This may lead to a localized abscess or, if adjacent organs are involved, a fistula or obstruction. Poor containment of the inflamed diverticulum or abscess results in free perforation and peritonitis.
Segmental colitis associated with diverticula — The pathogenesis of segmental colitis associated with diverticula (SCAD) or diverticular colitis is incompletely understood. The cause may be multifactorial, related to mucosal prolapse, fecal stasis, or localized ischemia [65]. Other theories suggest that alterations in the gut microbiota and chronic inflammation result in SCAD. (See "Segmental colitis associated with diverticulosis".)
Symptomatic uncomplicated diverticular disease — Altered colonic motility may be one of the underlying causes of abdominal pain and constipation in patients with symptomatic uncomplicated diverticular disease (SUDD). In one study, patients with SUDD displayed an increase in duration of rhythmic, low-frequency contractile activity particularly in segments of the colon with diverticula [66]. In another study, patients with diverticulosis were demonstrated to have a significantly reduced density of interstitial cells of Cajal as compared with controls, suggesting that abnormal colonic motility may be the underlying basis of symptoms in patients with SUDD [67].
It has also been hypothesized that visceral hypersensitivity plays an important role in the pathogenesis of SUDD. A study compared colonic visceral pain perception in response to luminal distention in patients with SUDD, asymptomatic diverticulosis, and healthy controls. In this study, patients with SUDD but not asymptomatic diverticulosis and healthy controls demonstrated a heightened pain perception both in the sigmoid colon with diverticula and in the unaffected rectum. The mechanism of hypersensitivity in patients with SUDD may relate to increased neuropeptides and alterations in enteric innervation following an episode of diverticulitis [68].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Colonic diverticular disease".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Diverticulitis (The Basics)")
●Beyond the Basics topics (see "Patient education: Diverticular disease (Beyond the Basics)")
SUMMARY
●A diverticulum is a sac-like protrusion of the colonic wall. Diverticulosis merely describes the presence of diverticula. These may not be symptomatic or complicated. Diverticular disease is defined as clinically significant and symptomatic diverticulosis. Diverticular symptoms may be due to diverticular bleeding, symptomatic uncomplicated diverticular disease, diverticulitis, or segmental colitis associated with diverticulosis. (See 'Definitions' above.)
●The prevalence of diverticulosis increases with age from less than 20 percent at age 40 to 60 percent by age 60. In the Western hemisphere, diverticulosis is predominantly left-sided, with prevalence rates of 5 to 45 percent. In contrast, in Asia, the prevalence of diverticulosis is lower and diverticulosis is predominantly right-sided. Among patients with diverticulosis, bleeding occurs in approximately 5 to 15 percent, with the right colon being the source of colonic diverticular bleeding in 50 to 90 percent of patients. Approximately 5 to 15 percent of patients with diverticulosis develop diverticulitis. (See 'Epidemiology' above.)
●Dietary fiber is associated with a decreased risk of symptomatic diverticular disease. A diet high in total fat and red meat is associated with an increased risk of symptomatic diverticular disease. There is no association between nut, corn, and popcorn consumption and the risk of diverticulosis and diverticular bleeding.
Vigorous physical activity appears to reduce the risk of diverticulitis and diverticular bleeding. Obesity and several medications (eg, nonsteroidal anti-inflammatory drugs, steroids, and opiates) are associated with an increased risk of diverticulitis and diverticular bleeding. Statins may be associated with a decreased risk of diverticular perforation. (See 'Risk factors' above.)
●Diverticula occur at points of weakness in the bowel wall where blood vessels penetrate (figure 1). The development of diverticula is probably multifactorial, involving both increases in intraluminal pressure caused by abnormalities in motility and histologic abnormalities in the bowel wall, which decrease tensile strength. (See 'Diverticulosis' above.)
●Segmental weakness of the artery in the diverticular wall predisposes to rupture into the lumen, resulting in a diverticular bleed (picture 2). In contrast, the underlying cause of diverticulitis is micro- or macroscopic perforation of the diverticulum itself. The inflammation is frequently mild, and a small perforation is walled off by pericolic fat and mesentery. This may lead to a localized abscess or, if adjacent organs are involved, a fistula or obstruction. Poor containment of the inflamed diverticulum or abscess results in free perforation and peritonitis. (See 'Diverticular bleeding' above and 'Diverticulitis' above.)
●Alterations in the gut microbiome, chronic inflammation, and visceral hypersensitivity have been implicated in the pathogenesis of segmental colitis associated with diverticula and symptomatic uncomplicated diverticular disease. (See 'Segmental colitis associated with diverticula' above and 'Symptomatic uncomplicated diverticular disease' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Tonia Young-Fadok, MD, who contributed to an earlier version of this topic review.
