The physician may elect to limit the extent of the initial exam if severe colitis is encountered to minimize the risk of perforation of the colon. However, a complete colonoscopy with entry into the terminal ileum should be performed to rule out Crohns disease, and assess extent and severity of disease. Endoscopic findings in ulcerative colitis include: erythema (redness of the mucosa), friability of the mucosa, superficial ulceration, and loss of the vascular appearance of the colon. When present, ulcerations may be confluent. Pseudopolyps may be observed.Ulcerative colitis is usually continuous from the rectum, with the rectum almost universally being involved. Perianal disease is rare. The degree of involvement endoscopically ranges from proctitis (rectal inflammation) to left sided colitis (extending to descending colon), to extensive colitis (extending proximal to descending colon). Histologic
Biopsies of the mucosa are taken during endoscopy to confirm the diagnosis of UC and differentiate it from Crohns disease, which is managed differently clinically. Histologic findings in ulcerative colitis includes: distortion of crypt architecture, crypt abscesses, and inflammatory cells in the mucosa (lymphocytes, plasma cells, and granulocytes). Unlike the transmural inflammation seen in Crohns disease, the inflammation of ulcerative colitis is limited to the mucosa. Laboratory tests
Blood and stool tests serve primarily to assess disease severity, level of inflammation and rule out causes of infectious colitis. All individuals with suspected ulcerative colitis should have stool testing to rule out infection.A complete blood count may demonstrate anemia, leukocytosis, or thrombocytosis. Anemia may be caused by inflammation or bleeding.
Other findings may include colonic dilation and stool buildup evidencing constipation.Similar to xray, in mild ulcerative colitis, double contrast barium enema often shows nonspecific findings. Conversely, barium enema may display small buildups of barium in microulcerations. Severe UC can be characterized by various polyps, colonic shortening, loss of haustrae (the small bulging pouches in the colon),and narrowing of the colon. It is important to note that barium enema should not be conducted in patients exhibiting very severe symptoms as this may slow or stop stool passage through the colon causing ileus and toxic megacolon.Other methods of imaging include computed tomography (CT) and magnetic resonance imaging (MRI). Both may depict colonic wall thickening but have decreased ability to find early signs of wall changes when compared to barium enema. In cases of severe ulcerative colitis, however, they often exhibit equivalent ability to detect colonic changes.Doppler ultrasound is the last means of imaging that may be used. Similar to the imaging methods mentioned earlier, this may show some thickened bowel wall layers. In severe cases, this may show thickening in all bowel wall layers (transmural thickness). Differential diagnosis
Several conditions may present in a similar manner as ulcerative colitis, and should be excluded. Such conditions include: Crohns disease, infectious colitis, nonsteroidal anti-inflammatory drug enteropathy, and irritable bowel syndrome. Alternative causes of colitis should be considered, such as ischemic colitis (inadequate blood flow to the colon), radiation colitis (if prior exposure to radiation therapy), or chemical colitis. Pseudomembranous colitis may occur due to Clostridioides difficile infection following administration of antibiotics.