Ulcerative colitis is one of the 2 major types of inflammatory bowel disease (IBD), along with Crohn disease. Unlike Crohn disease, which can affect any part of the gastrointestinal tract, ulcerative colitis characteristically involves the large bowel .
The exact etiology of ulcerative colitis is unknown, but the disease appears to be multifactorial and polygenic. Proposed causes include 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.
Ulcerative colitis is a lifelong illness that has a profound emotional and social impact on affected patients.
Grossly, the colonic mucosa appears hyperemic, with loss of the normal vascular pattern. The mucosa is granular and friable. Frequently, broad-based ulcerations cause islands of normal mucosa to appear polypoid, leading to the term pseudopolyp
The bowel wall is thin or of normal thickness, but 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 very rare; such involvement is seen in patients with severe disease, particularly toxic dilatation, and reflects a secondary effect of the severe disease rather than primary ulcerative colitis pathogenesis. 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.
The diagnosis of ulcerative colitis is best made with endoscopy and mucosal biopsy for histopathology. Laboratory studies are helpful to exclude other diagnoses and assess the patient's nutritional status, but serologic markers can assist in the diagnosis of inflammatory bowel disease. Radiographic imaging has an important role in the workup of patients with suspected inflammatory bowel disease and in the differentiation of ulcerative colitis from Crohn disease by demonstrating fistulae or the presence of substantial coexisting more proximal small bowel disease in a patient who turns out to actually have Crohn disease.
Ulcerative colitis extends proximally from the anal verge in an uninterrupted pattern to involve part or the entire colon. The rectum is involved in more than 95% of cases; some authorities believe that the rectum is always involved in untreated patients. Rectal involvement occurs even when the rest of the colon is spared.
Ulcerative colitis occasionally involves the terminal ileum, as a result of an incompetent ileocecal valve. In these cases, which may constitute as many as 10% of patients, the reflux of noxious inflammatory mediators from the colon results in superficial mucosal inflammation of the terminal ileum, called backwash ileitis.. About 30 cm of the terminal ileum is usually affected.
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