Diverticulosis is a clinical condition in which multiple sac-like protrusions (diverticula) develop along the gastrointestinal tract. Though diverticula may form at weak points in the walls of either the small or large intestines, the majority occur in the large intestine (most commonly the sigmoid colon).
The majority of individuals with diverticulosis are asymptomatic. Diverticular disease occurs when there is symptomatic diverticulosis (e.g., diverticular bleeding); diverticulitis (e.g., acute or chronic inflammation that may or may not is complicated by abscess formation, fistula formation, bowel obstruction or perforation); or associated segmental colitis (e.g., inflammation in segments of the mucosal segments of colon in between diverticula).
Diverticulosis is thought to occur as a result of peristalsis abnormalities (e.g., intestinal spasms), intestinal dyskinesia, or high segmental intraluminal pressures. Although the exact cause of these abnormalities is unknown, some environmental and lifestyle risk factors have been linked to this condition.
Several studies have suggested that a diet low in fiber and high in red meat may be associated with an increased risk of diverticulosis, although a diet high in fiber will not reduce the symptoms of an uncomplicated diverticular disease. In patients with symptomatic complicated diverticular disease (e.g., inflammation or bleeding) there may be benefit from a diet high in fiber by decreasing overall inflammation and favorably changing the intestinal microbiota.
The risk of diverticulitis and bleeding is significantly higher in patients with obesity or a larger waist circumference.
Smokers have been noted to have an increased incidence of diverticular abscess formation or perforation.
Medications associated with an increased risk of diverticular bleeding or diverticulitis include nonsteroidal anti-inflammatory drugs, opiates, and steroids.
The prevalence of diverticulosis is highest in the Western world and in countries that follow a more Western lifestyle. Diverticulosis affects 5% to 45% of individuals in the Western world, depending on both the method of diagnosis and age of the individual. In general, the prevalence of diverticulosis increases with age from under 20% of individuals affected at the age of 40, to 60% of individuals affected by the age of 60. Approximately 95% of patients in the Western world with diverticulosis have diverticula in the sigmoid colon. Of all of the patients with diverticulosis, 24% have diverticula involving mainly the sigmoid colon, 7% have diverticula spread evenly throughout the colon, and 4% have diverticula located only proximally to the sigmoid colon.
In Asia, diverticulosis has a prevalence of approximately 13% to 25%. Individuals with diverticulosis in this region also tend to have predominantly right-sided colonic diverticula (unlike the Western world where left-sided diverticula are much more common).
Approximately 5% to 15% of patients with diverticulosis experience bleeding. A third of which experience massive bleeding. In 50% to 60% of patients experiencing diverticular bleeding, the source is right-sided diverticula, possibly due to the thinner wall of the right-sided colon or the wider neck and domes of right-sided diverticula (e.g., increased surface area of exposure of the vasa recta to potential injury).
Diverticulitis occurs in approximately 4% to 15% of patients with diverticula, and the incidence increases with age. On average, patients admitted for diverticulitis are about 63 years old. The overall incidence of diverticulitis continues to rise, with a 26% jump from 1998 to 2005, and the largest increases were seen in patients between the ages 18 to 44 years.
Under the age of 50, diverticulosis is more common in males, whereas between the ages of 50 to 70, the disease is seen slightly more often in females. Over the age of 70, there is a significantly greater incidence of diverticulosis in females.
Diverticula occur in weaker portions of the colonic wall where the vasa recta infiltrate the circular muscular layer. The vast majority of colonic diverticula are typically “false” diverticula which are mucosa and submucosa herniating through a defect or weakness in the muscularis layer, covered externally only by serosa. True diverticula are much more uncommon (e.g., Meckel’s diverticulum) and involve outpouching of all layers of the intestinal wall (e.g., mucosa, muscularis, and serosa).
A major predisposing factor for the formation of colonic diverticula is abnormal colonic motility (e.g., intestinal spasms or dyskinesis) resulting in exaggerated segmental muscle contractions, elevated intraluminal pressures, and separation of the colonic lumen into chambers. The increased incidence of diverticula in the sigmoid colon is explained by Laplace’s law, such that pressure is proportional to wall tension and inversely proportional to bowel radius. As the sigmoid colon is the segment of colon with the smallest diameter, it is also the segment with highest intraluminal pressures.
Connective tissue disorders such as Marfan syndrome, Ehlers-Danlos syndrome, or autosomal dominant polycystic kidney disease may additionally predispose an individual to the formation of colonic diverticula as these diseases often involve structural changes (e.g., weakness) in the intestinal wall.
Diverticula are prone to bleeding due to the proximity of the vasa recta to the intestinal lumen as a result of herniation of the mucosa and submucosa through the muscularis layer. With diverticula formation, the vasa recta become separated from the intestinal lumen by a layer of mucosa alone and are therefore exposed to a greater amount of injury. This results in eccentric intimal thickening, thinning of the media, and ultimately segmental weaknesses along these arteries which predispose the vasa recta to rupture and bleeding into the intestinal lumen. Diverticular bleeding typically occurs in the absence of diverticular inflammation or infection (i.e., diverticulitis).
Diverticulitis typically results from micro- or macroscopic perforation of a diverticulum, and this may or may not result from obstruction (e.g., by a fecalith). Increased intraluminal pressures or inspissated (thickened and condensed) food matter, with resultant inflammation and focal necrosis, are what ultimately result in diverticular perforation. Associated inflammation is usually mild, and pericolic fat and mesentery tend to wall off the perforations of diverticula. This may or may not result in abscess or fistula formation, or intestinal obstruction. In rare cases, perforations may be large and uncontained and lead to peritonitis.
Most individuals with diverticulosis do not have any symptoms, and the condition itself is not dangerous. Some patients, however, may experience unexplained abdominal pain or cramping, alterations in bowel habits, or notice blood in the stool. Any bleeding associated with diverticulosis is painless.
A diagnosis of diverticulosis is suspected when a patient presents with a history of painless rectal bleeding or unexplained abdominal pain or cramping, or alterations in bowel function.
Acute diverticulitis (e.g., inflammation, infection, or perforation) is typically suspected when a patient presents with lower abdominal pain (particularly on the left side). Patients may additionally present with abdominal tenderness to palpation and an elevated white blood cell count (leukocytosis). An abdominal CT will help differentiate between complicated versus uncomplicated disease in this case.
A diagnosis of diverticulosis is suspected based on clinical presentation (e.g., history of painless rectal bleeding or unexplained abdominal pain and cramping, or altered bowel movements) and may be confirmed by colonoscopy or an x-ray following a barium enema. If the patient presents with extreme abdominal pain, however, the test of choice is typically a CT of the abdomen to avoid the risk of intestinal rupture in the setting of intestinal infection or inflammation.
A colonoscopy remains the best test to identify the source of bleeding if blood is present in the stool. If a colonoscopy is inconclusive, however, angiography or radionuclide scanning may be considered to locate the source.
Patients presenting with acute diverticulitis may require additional treatment. Uncomplicated diverticulitis is treated non-operatively, with either intravenous (IV) or oral (PO) antibiotics. Complicated diverticulitis (e.g., with an associated fistula, abscess, obstruction, or perforation) may, in addition to antibiotic therapy, require hospitalization and/or surgery, to treat the associated complication. Similarly, patients presenting with sepsis, immunosuppression, advanced age, significant comorbidities, high fever (greater than 39.2°C), significant leukocytosis, inability to tolerate oral intake, non-compliance, or failed outpatient treatment, may require hospitalization for proper treatment.
Treatment is typically aimed at reducing intestinal spasms which may be achieved by increasing fiber and fluids in the diet. Greater intestinal bulk reduces the number of spasms, and as a result decreases intestinal pressures. Most bleeding associated with diverticulosis is self-limiting and does not require intervention. In some cases, however, endoscopic, radiologic, or surgical intervention may be required to stop persistent bleeding ((e.g., injection, coagulation (cautery, argon plasma coagulator), or mechanical devices (clips, bands, loops)). In the case of recurrent bleeding, or if a source cannot be determined, surgery may be considered to remove portions of affected intestine (e.g., colectomy). Similarly, in the case of a giant diverticulum, with an increased risk of infection and rupture, surgery is more likely to be considered.