Crohn's Disease: Background and Diagnosis
Crohn’s disease can attack any portion of the digestive tract, although inflammation most commonly occurs in the lower portion of the small intestine, known as the ileum. The disease can cause ulcerations within the intestine that can erode into surrounding tissues such as the bladder (Sato 1999), vagina (Feller 2001), or even the surface of the skin (Tavarela 2004). Inflammation in Crohn’s disease is not limited to the intestine—some people who have Crohn’s disease have inflammation of the eyes and joints as well.
The most common symptoms of the disease include severe abdominal pain with or without diarrhea. Diarrheal stool may be mixed with blood, mucus and/or pus. Bowel movements are often painful. Cramping in the right lower side of the abdomen is common, especially after meals. People with Crohn’s disease often have chronic low-grade fever, poor appetite, fatigue, and weight loss. Skin rashes may also occur. People who have Crohn’s disease often have some degree of anemia, related to poor iron, folic acid, and/or vitamin B12 absorption and due to chronic blood loss. Those with mild Crohn’s can eat and function reasonably normally, while those with severe disease often fail to respond to conventional treatment and have persistent gastrointestinal symptoms, as well as fevers, and infections. Blood tests for ferritin, which measures iron storage, and vitamin B12 and folate can help detect deficiencies due to malabsorption.
Diagnosis of Crohn’s disease is usually based on a patient’s medical history and symptoms. Diagnostic tests may be used to confirm the disease and to distinguish it from ulcerative colitis. Such tests include x-rays (with contrast material such as barium), colonoscopy, and endoscopy.
No blood test can diagnose Crohn’s disease, but routine testing is usually done to detect anemia, infection, degree of inflammation, and determine liver function. Certain markers of inflammation, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) may be used to follow a patient’s course over time. The anti-Saccharomyces cerevisiae antibody (ASCA) blood test is sometimes used to help differentiate Crohn’s disease from ulcerative colitis (Vermeire 2001).
There is a high prevalence of Celiac disease in people with Crohn’s disease (Tursi 2005). Celiac disease blood testing such as tissue transglutaminase and anti-gliadin antibodies should be considered in Crohn’s.
Ulcerative Colitis: Background and Diagnosis
Ulcerative colitis is characterized by inflammation of the large intestine (colon) that leads to episodes of bloody diarrhea, abdominal cramping, and even fever. Unlike Crohn’s disease, ulcerative colitis usually does not affect the full thickness of the intestine and rarely affects the small intestine. The disease usually begins in the rectum or sigmoid colon and spreads partially or completely through the large intestine.
Ulcerative colitis typically begins gradually, with abdominal pain and diarrhea that is sometimes bloody. In more serious cases, diarrhea is severe and frequent. Fever, loss of appetite, and weight loss occur. The severity of the disease depends on how much of the colon is involved. For many patients, there may be long periods with no symptoms at all, followed by flare-ups.
A definitive diagnosis can be made by direct examination of the colon by sigmoidoscopy (examination of the lower portion only) or colonoscopy (examination of the entire colon, the preferred approach). Both procedures can be used to take a biopsy of intestinal tissue, which can reveal important information about the degree and extent of inflammation and help rule out other causes of symptoms. A barium enema x-ray of the colon may also be required at some point in the course of colitis to determine the extent of involvement. Once diagnosed, ulcerative colitis can be categorized based on disease severity as follows:
- Severe. Severe ulcerative colitis, which involves the whole colon, is the least common form of the disease. Symptoms consist of profuse bloody diarrhea (occurring six or more times per day), often with a sustained fever and tachycardia (rapid heart rate). Severe anemia, increased white blood cell count, and decreased serum albumin levels are also characteristic symptoms.
- Moderate. Symptoms consist of recurrent diarrhea, small amounts of blood in the stool, possible low-grade fever, mild anemia, and minimal signs of inflammation. Moderate ulcerative colitis responds quickly to appropriate therapies. However, repeated attacks of equal or increased severity can occur, which can significantly increase the risk of developing colon cancer later.
- Mild. Mild ulcerative colitis is the most common form of the disorder, occurring in about 50 percent of patients. In most cases, ulcerative colitis will be limited to the lower portion of the colon and the rectum. Systemic complications are uncommon and the primary symptom is rectal bleeding.