Introduction
Background
Ulcerative colitis is a type of inflammatory bowel disease (IBD) that characteristically involves the large bowel. It is a multifactorial polygenic disease; the exact etiology is unknown. Included in the etiologic theories are environmental factors, immune dysfunction, and a likely genetic predisposition. Some have suggested that children of below-average birth weight who are born to mothers with ulcerative colitis have a greater risk of developing the disease.
Single-contrast enema study in a patient with total colitis shows mucosal ulcers with a variety of shapes, including collar-button ulcers, in which undermining of the ulcers occurs, and double-tracking ulcers, in which the ulcers are longitudinally orientated.
Postevacuation image obtained after a single-contrast barium enema study shows extensive mucosal ulceration resulting from Shigella colitis.
Histocompatibility human leukocyte antigen (HLA)–B27 is identified in most patients with ulcerative colitis, though this finding is not associated with the condition. Immune dysfunction has been postulated as a cause, although the clear evidence of this is limited. Ulcerative colitis might also be linked to diet, though diet is thought to play a secondary role. Food or bacterial antigens might exert an effect on the already damaged mucosal lining, which has increased permeability.
For excellent patient education resources, visit eMedicine's Crohn Disease Center and Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education articles Crohn Disease and Crohn Disease FAQs.
Ulcerative Colitis (from Gastroenterology)
Ulcerative Colitis: Surgical Perspective
Pathophysiology
Ulcerative colitis involves only the mucosa; it is characterized by the formation of crypt abscesses and a coexisting depletion of goblet cell mucin. In severe cases, the submucosa may be involved; in some cases, the deeper muscular layers of the colonic wall is also affected.
Acute severe colitis may result in a fulminant colitis or toxic megacolon, which is characterized by a thin-walled, large, dilated colon that may eventually become perforated. Chronic disease is associated with pseudopolyp formation in about 15-20% of cases. Chronic and severe cases can be associated with areas of precancerous changes, such as carcinoma in situ or dysplasia.
Anatomically, the large majority of cases involve the rectum; some patients develop terminal ileitis caused by an incompetent ileocecal valve. In these cases, about 30 cm of the terminal ileum is usually affected.
The following immunologic changes have been documented:
- Subsets of T cells accumulate in the lamina propria of the diseased colonic segment. In patients with ulcerative colitis, these T cells are cytotoxic to colonic epithelium. This change is accompanied by an increase in the population of B cells and plasma cells, with increased production of immunoglobulin G (IgG) and immunoglobulin E (IgE).1
- Colonic biopsy samples from patients with ulcerative colitis may show significantly increased levels of platelet-activating factor (PAF). PAF release, stimulated by leukotrienes, endotoxin, or other factors, may be responsible for the mucosal inflammation; however, this process is not clear.
- Anticolonic antibodies have been detected in patients with ulcerative colitis.
- A small proportion of patients with ulcerative colitis have smooth muscle and anticytoskeletal antibodies.
The bowel wall is thin or of normal thickness, but the presence of edema, the accumulation of fat, and hypertrophy of the muscle layer may give the impression of a thickened bowel wall. The disease is largely confined to the mucosa and, to a lesser extent, the submucosa. Muscle-layer and serosal involvement is rare; such involvement is seen in those with severe disease, particularly toxic dilatation. Early disease manifests as hemorrhagic inflammation with loss of the normal vascular pattern; petechial hemorrhages; and bleeding. Edema is present, and large areas become denuded of mucosa. Undermining of the mucosa leads to the formation of crypt abscesses, which are the hallmark of the disease.
Microscopic changes include inflammation of the crypts of Lieberkuhn and abscesses. These findings are accompanied by a discharge of mucus from the goblet cells, the number of which is reduced as the disease progresses. The ulcerated areas are soon covered by granulation tissue. Excessive fibrosis is not a feature of the disease. The undermining of mucosa and an excess of granulation tissue lead to the formation of polypoidal mucosal excrescences, which are known as inflammatory polyps or pseudopolyps.
Frequency
United States
In the Western world, ulcerative colitis has a prevalence of 3-10 cases per 100,000 population. Ulcerative colitis is 3 times more common than Crohn disease.
International
Geographically, ulcerative colitis is more common in the Western and Northern hemispheres; the incidence is low in Asia and the Far East.
Mortality/Morbidity
Ulcerative colitis may result in disease-related mortality. However, overall mortality is not increased in patients with ulcerative colitis, as compared with the general population. An increase in mortality may be observed among elderly patients with the disease. Mortality is also increased in patients who develop complications (eg, shock, malnutrition, anemia). Evidence suggests that mortality is increased in patients with ulcerative colitis who undergo any form of medical or surgical intervention.
- The most common cause of death of patients with ulcerative colitis is toxic megacolon.
- Colonic adenocarcinoma develops in 3-5% of patients with ulcerative colitis. The risk increases as the duration of disease increases. The risk of colonic malignancy is higher in cases of pancolitis and in cases in which disease occurs before the age of 15 years.
- Benign stricture rarely causes intestinal obstruction.
Race
Ulcerative colitis is more common in individuals living in temperate climates and in whites. There are sporadic increases in some Jewish populations. The disease is uncommon in the Far East.
Sex
Ulcerative colitis is slightly more common in men than in women.
Age
Ulcerative colitis is uncommon in persons younger than 10 years. Most patients are 20-40 years of age at diagnosis. Another peak occurs at 60 years of age.
Anatomy
Ulcerative colitis predominantly affects the colon and, occasionally, the terminal ileum. In terms of anatomic distribution, ulcerative colitis may be classified as colonic or extracolonic. As a rule, ulcerative colitis involves the rectum, even when the rest of the colon is spared. In some patients with pancolitis, the terminal ileum displays a superficial mucosal inflammation called backwash ileitis.
Carcinoma is a known complication of ulcerative colitis in the small group of patients who have had the disease for approximately 10 years. The cancer tends to be multicentric, atypical in its appearance, and rapidly metastasizing.
Presentation
Patients with ulcerative colitis predominantly complain of increasing fresh bleeding from the rectum, with frequent stools and mucus discharge from the rectum. In severe cases, purulent rectal discharge causes lower abdominal pain and severe dehydration, especially in the elderly population. Some patients also describe tenesmus.
Findings from abdominal examination are usually unremarkable. The diagnosis is best made with endoscopy; findings include an abnormal erythematous mucosa, with or without ulceration. Contact bleeding may also be observed, with mucus identified in the lumen of the bowel.
Biopsy of the mucosa is recommended to identify the extent of the disease with respect to the thickness of the bowel wall. A barium enema may also be administered to identify a tubular colon. Routine blood tests to be performed include assays for C-reactive protein and serum albumin. In cases of toxic megacolon, perforation is always a risk; this renders the patients acutely unwell.
The severity of ulcerative colitis can be graded as follows:
- Mild — Bleeding per rectum and fewer than 4 bowel motions per day
- Moderate — Bleeding per rectum with more than 4 bowel motions per day
- Severe — Bleeding per rectum, more than 4 bowel motions per day, and a systemic illness with hypoalbuminemia (<30 g/L)
Preferred Examination
Plain abdominal radiographs are a useful adjunct to imaging in cases of ulcerative colitis of acute onset. In severe cases, the images may show colonic dilatation, suggesting toxic megacolon; evidence of perforation; obstruction; or ileus. Radiographic imaging has an important role in the workup of patients with suspected IBD and in the differentiation of ulcerative colitis and Crohn disease. Because of its ability to depict fine mucosal detail, double-contrast barium enema examination is a valuable technique for diagnosing ulcerative colitis and Crohn disease, even in patients with early disease. Traditionally, barium enema examination has been the mainstay of radiologic investigation for suspected ulcerative colitis.2,3,4,5
Transabdominal ultrasonography (US) is a noninvasive modality that may be helpful in the diagnosis of IBD, but it cannot be used to distinguish between ulcerative colitis and Crohn disease. US is also a useful technique in the investigation of biliary complications of the disease.
Generally, CT has a limited role in the diagnosis of uncomplicated ulcerative colitis. However, CT plays an important role in the differential diagnosis of ulcerative colitis, and it is an excellent modality in the diagnosis of complications associated with the disease. Biliary dilatation suggests primary sclerosing cholangitis.
Cross-sectional imaging studies such as CT, MRI, and US are useful for showing the effects of these conditions on the wall of the bowel and for demonstrating intra-abdominal abscesses and other extraluminal findings in patients with more advanced disease. Thus, barium studies and cross-sectional imaging studies have complementary roles in the evaluation of ulcerative colitis.
Radionuclide studies are useful in cases of acute fulminant colitis when colonoscopy or barium enema examination is contraindicated. Radionuclide studies are also useful in depicting disease activity and the extent of disease and in monitoring the response to therapy.
Limitations of Techniques
All imaging techniques lack specificity. Mucosal ulceration depicted on barium studies is nonspecific and is encountered in a variety of colitides. In severe cases, barium enema may precipitate toxic megacolon. Generally, barium enemas may be performed safely only in mild cases. Thickening of the bowel wall, as seen on cross-sectional imaging (CT, MRI, and US), is a nonspecific finding seen in a variety of bowel conditions besides IBD. Increased radionuclide focal activity may be related to a variety of physiologic and pathologic conditions unrelated to ulcerative colitis. Motion artifacts may interfere with cross-sectional imaging. Although this is not a major problem with modern scanners, some investigators still use a hypotonic agent to decrease bowel peristalsis.
Differential Diagnoses
Other Problems to Be Considered
Radiologic findings in cases of acute infective enterocolitis from infection caused by Entamoeba histolytica (amebiasis), cytomegaloviral colitis, and Isospora, Salmonella, Shigella, or Yersinia may be similar to the findings seen in cases of ulcerative colitis; this is especially true with CT scans.
Prolonged use of cathartics, especially cascara, over many years may lead to a condition known as cathartic colon. The radiologic appearance of cathartic colon is similar to that of ulcerative colitis. In cathartic colon, the changes are more marked in the right hemicolon than in the left. The bowel is distensible, and there are inconstant areas of bowel narrowing and loss of haustra.
More on Ulcerative Colitis |
 Overview: Ulcerative Colitis |
| Imaging: Ulcerative Colitis |
| Follow-up: Ulcerative Colitis |
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Further Reading
Keywords
ulcerative colitis, UC, inflammatory bowel disease, IBD, ulcerative proctocolitis, crypt abscesses, fulminant colitis, toxic megacolon, Crohn disease, Crohn's disease, CD
