Endoscopic image of<unk>  affecting the left side of the colon. The image shows confluent superficial ulceration and loss of mucosal architecture. Crohn's disease may be similar in appearance, a fact that can make diagnosing<unk>  a challenge. H&E stain of a colonic biopsy showing a crypt abscess, a classic finding in<unk>  The initial diagnostic workup for<unk>  consists of a complete history and physical examination, assessment of signs and symptoms, laboratory tests and endoscopy. Specific testing may include the following: * A complete blood count is done to check for anemia; thrombocytosis, a high platelet count, is occasionally seen * Electrolyte studies and kidney function tests are done, as chronic diarrhea may be associated with hypokalemia, hypomagnesemia and kidney injury. * Liver function tests are performed to screen for bile duct involvement: primary sclerosing cholangitis. * Imaging such as x-ray or CT scan to evaluate for possible perforation or toxic megacolon * Stool culture and Clostridioides difficile stool assay to rule out infectious colitis * Inflammatory markers, such as erythrocyte sedimentation rate or C-reactive protein * Lower endoscopy to evaluate the rectum and distal large intestine (sigmoidoscopy) or entire colon and end of the small intestine (colonoscopy) for ulcers and inflammation Although<unk>  is a disease of unknown causation, inquiry should be made as to unusual factors believed to trigger the disease. The simple clinical colitis activity index was created in 1998 and is used to assess the severity of symptoms. Endoscopic Colonic pseudopolyps of a person with intractable<unk> , colectomy specimen The best test for diagnosis of<unk>  remains endoscopy, which is examination of the internal surface of the bowel using a flexible camera. Initially, a flexible sigmoidoscopy may be completed to establish the diagnosis. 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 Crohn's disease, and assess extent and severity of disease. Endoscopic findings in<unk>  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.<unk>  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 Biopsy sample (H&E stain) that demonstrates marked lymphocytic infiltration (blue/purple) of the intestinal mucosa and architectural distortion of the crypts. Biopsies of the mucosa are taken during endoscopy to confirm the diagnosis of<unk>  and differentiate it from Crohn's disease, which is managed differently clinically. Histologic findings in<unk>  includes: distortion of crypt architecture, crypt abscesses, and inflammatory cells in the mucosa (lymphocytes, plasma cells, and granulocytes). Unlike the transmural inflammation seen in Crohn's disease, the inflammation of<unk>  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<unk>  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. Chronic blood loss may lead to iron deficiency as a cause for anemia, particularly microcytic anemia (small red blood cells), which can be evaluated with a serum ferritin, iron, total iron-binding capacity and transferrin saturation. Anemia may be due to a complication of treatment from azathioprine, which can cause low blood counts, or sulfasalazine, which can result in folate deficiency. Thiopurine metabolites (from azathioprine) and a folate level can help.<unk>  may cause high levels of inflammation throughout the body, which may be quantified with serum inflammatory markers, such as CRP and ESR. However, elevated inflammatory markers are not specific for<unk>  and elevations are commonly seen in other conditions, including infection. In addition, inflammatory markers are not uniformly elevated in people with<unk> . Twenty five percent of individuals with confirmed inflammation on endoscopic evaluation have a normal CRP level. Serum albumin may also be low related to inflammation, in addition to loss of protein in the GI tract associated with bleeding and colitis. Low serum levels of vitamin D are associated with<unk> , although the significance of this finding is unclear. Specific antibody markers may be elevated in<unk> . Specifically, perinuclear antineutrophil cytoplasmic antibodies (pANCA) are found in 70 percent of cases of<unk> . Antibodies against Saccharomyces cerevisiae may be present, but are more often positive in Crohn's disease compared with<unk> . However, due to poor accuracy of these serolologic tests, they are not helpful in the diagnostic evaluation of possible inflammatory bowel disease. Several stool tests may help quantify the extent of inflammation present in the colon and rectum. Fecal calprotectin is elevated in inflammatory conditions affecting the colon, and is useful in distinguishing irritable bowel syndrome (noninflammatory) from a flare in inflammatory bowel disease. Fecal calprotectin is 88% sensitive and 79% specific for the diagnosis of<unk> . If the fecal calprotectin is low, the likelihood of inflammatory bowel disease are less than 1 percent. Lactoferrin is an additional nonspecific marker of intestinal inflammation. Imaging Imaging tests, such as x-ray or CT scan, may be helpful in assessing for complications of<unk> , such as perforation or toxic megacolon. Bowel ultrasound (US) is a cost-effective, well-tolerated, non-invasive and readily available tool for the management of patients with inflammatory bowel disease (IBD), including<unk> , in clinical practice. Imaging is otherwise of limited use in diagnosing<unk> . Magnetic resonance imaging (MRI) is necessary to diagnose underlying PSC. Differential diagnosis Several conditions may present in a similar manner as<unk> , and should be excluded. Such conditions include: Crohn's 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. Entamoeba histolytica is a protozoan parasite that causes intestinal inflammation. A few cases have been misdiagnosed as<unk>  with poor outcomes occurring due to the use of corticosteroids. The most common disease that mimics the symptoms of<unk>  is Crohn's disease, as both are inflammatory bowel diseases that can affect the colon with similar symptoms. It is important to differentiate these diseases since their courses and treatments may differ. In some cases, however, it may not be possible to tell the difference, in which case the disease is classified as indeterminate colitis.
Ulcerative colitis
Crohn's disease
Diversion colitis
Dysentery
Collagenous colitis
Ischemic colitis
Microscopic colitis
Chemical colitis