Introduction
Background
Diverticular disease of the colon begins as diverticulosis (colonic outpouchings), which may develop into diverticulitis (diverticular inflammation and perforation).1
For excellent patient education resources, visit eMedicine's Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education article Diverticulosis and Diverticulitis.
Pathophysiology
Diverticula can be either acquired or congenital, and they can affect either the small intestine or the large intestine. Acquired diverticula are more common and consist of herniation of the mucosa and submucosa through the muscularis, usually at the site of a nutrient artery. Congenital diverticula are outpouchings of the entire thickness of the intestinal wall. The exact mechanism of formation of acquired diverticula is unknown, but they may be related to an increase in intramural pressure. Diverticula usually occur adjacent to the vasa recta, the small vessels that extend into the submucosa, because these are the weakest areas of the colonic wall. Therefore, diverticula usually occur on the mesenteric side of the colon.
Because colonic diverticula are rare in the populations of underdeveloped nations, in contrast to the frequent occurrence in Western countries, theories propose that diverticula result from the highly refined Western diet that is deficient in dietary fiber. This diet results in decreased fecal bulk, narrowing of the colon, and increased intraluminal pressure for moving the smaller fecal mass. The major complications of diverticulosis are diverticulitis and hemorrhage.
Diverticulitis is inflammation in and around a diverticulum. The cause of diverticulitis is probably mechanical. The stagnation of nonsterile inspissated fecal material, termed a fecalith, within the diverticulum may compromise the blood supply to the thin-walled sac and render it susceptible to invasion by colonic bacteria, causing inflammatory erosion of the mucosal lining with perforation. This sequence of events can involve perforation into the colonic wall, with the formation of an intramural abscess. However, perforation usually occurs into the pericolic fat, leading to fibrinous exudate, abscess formation, local adhesions, or peritonitis. Most patients develop sealed-off abscesses or contained sinus tracts and fistulas. Fistulas usually involve adjacent structures, such as the bowel, urinary bladder, vagina, and anterior abdominal wall. Other potential complications include bowel obstruction and peritonitis.2
Frequency
United States
Diverticular disease is the most common colon disease in Western nations. In the West, colonic diverticula occur in 5% of the population by the time individuals are aged 40 years. They affect 33-50% of the population older than 50 years and more than 50% of the population older than 80 years.
Diverticulitis is the most common complication of diverticulosis, and it has been reported in 10-20% of patients with diverticulosis. The incidence of diverticulitis increases if the diverticula are numerous, if they have been present for more than a decade, and if they are distributed throughout the colon.
International
In underdeveloped nations in Asia and Africa, diverticulosis occurs in less than 0.2% of the population. This low rate is probably the result of a high-fiber diet. In immigrants to Western nations from Asia and Africa, the frequency of diverticulitis increases within 10 years.
Mortality/Morbidity
Approximately 20% of patients with diverticulitis require surgical treatment. In a study by Belmonte et al, patients with diverticulitis with pelvic abscesses or generalized peritonitis had a mortality rate of 7.7%.3 Of patients treated for diverticulitis, 5% experience a second occurrence within 2 years of the initial episode.
Race
The incidence of diverticulosis and diverticulitis is related primarily to diet rather than race. However, right-sided diverticula, which are usually congenital, occur most commonly in Asians.
Sex
The incidences of both diverticulosis and diverticulitis are similar in males and females.
Age
The incidence of diverticulosis and diverticulitis increases with age, and it is particularly common in patients older than 50 years.
Anatomy
Diverticula involve the sigmoid colon in as many as 95% of patients with diverticulosis. The cecum is involved in 5% of patients. The sigmoid is the narrowest portion of the colon, and it generates the highest intrasegmental pressures. The combination of numerous haustra and dehydrated stool in the sigmoid colon leads to segmentation in which it functions as multiple small compartments. These features account for the high incidence of diverticulosis in the sigmoid colon.
In Japan, right-sided diverticulosis is 5 times more common than left-sided diverticulosis. Sigmoid diverticula are usually acquired false diverticula and multiple. Right-sided diverticula are usually congenital and solitary.
Presentation
Typical features of sigmoid diverticulitis include fever, leukocytosis, and left lower quadrant pain. Other clinical features include nausea, vomiting, flatulence, palpable masses, muscle guarding, and partial obstruction. Patients with diverticulitis also may have elevated C-reactive protein (CRP) levels and erythrocyte sedimentation rates (ESRs). Mild bleeding occurs in as many as 25% of patients.
Diverticulitis is clinically more severe in younger patients, particularly in patients younger than 40 years. Complications of diverticulitis include pericolic abscess and fistulas within the small bowel, vagina, urinary bladder, and abdominal wall.4
Preferred Examination
The preferred examination is CT scanning of the abdomen and pelvis. CT findings can help in confirming clinical suspicion of diverticulitis and in excluding other abdominal or pelvic disease. CT can help in evaluating and in staging inflammatory disease. CT can also be used to accurately plan a percutaneous intervention.
Ultrasonography is occasionally useful in diagnosing acute diverticulitis. Ultrasonography is inexpensive, noninvasive, and readily available. Sonography could be used if CT is not available.
Traditionally, barium enema imaging has been the primary method of examining patients in whom diverticulitis is suspected. Barium studies superbly depict diverticula, the colonic mucosa and lumen, spasm, and muscle hypertrophy.5
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CME Diverticulitis Increasingly Diagnosed in Young, Obese Individuals
Limitations of Techniques
The major limitation of CT scanning is the potential difficulty in differentiating diverticulitis from colon carcinoma. Other limitations of CT are the high cost of the examination and its limited availability in certain regions of the world.
Ultrasonography might not be helpful in excluding diverticulosis or diverticulitis because of interference due to bowel gas.
Related Medscape topic:
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Differential Diagnoses
Other Problems to Be Considered
Epiploic appendagitis
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References
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Heise CP. Epidemiology and Pathogenesis of Diverticular Disease. J Gastrointest Surg. Feb 16 2008;[Medline].
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Kori T, Nemoto M, Maeda M, et al. Sonographic features of acute colonic diverticulitis: the "dome sign". J Clin Ultrasound. Sep 2000;28(7):340-6. [Medline].
Oudenhoven LF, Koumans RK, Puylaert JB. Right colonic diverticulitis: US and CT findings--new insights about frequency and natural history. Radiology. Sep 1998;208(3):611-8. [Medline].
Pradel JA, Adell JF, Taourel P, et al. Acute colonic diverticulitis: prospective comparative evaluation with US and CT. Radiology. Nov 1997;205(2):503-12. [Medline].
Hussain A, Mahmood H, Subhas G, El-Hasani S. Complicated diverticular disease of the colon, do we need to change the classical approach, a retrospective study of 110 patients in southeast England. World J Emerg Surg. 2008;3:5. [Medline].
Peppas G, Bliziotis IA, Oikonomaki D, Falagas ME. Outcomes after medical and surgical treatment of diverticulitis: a systematic review of the available evidence. J Gastroenterol Hepatol. Sep 2007;22(9):1360-8. [Medline].
Kassab A, El-Bialy G, Hashesh H, Callen P. Magnetic resonance imaging and hysteroscopy to diagnose colo-uterine fistula: A rare complication of diverticulitis. J Obstet Gynaecol Res. Feb 2008;34(1):117-20. [Medline].
Further Reading
Keywords
diverticulum, diverticulosis, diverticulitis, diverticular disease, diverticular disease of the colon, outpouching, diverticula, colonic diverticula, intestinal disease, diverticular hemorrhage, bowel obstruction, gastrointestinal hemorrhage, GI tract hemorrhage
