What is ulcerative colitis?
Ulcerative colitis is a chronic inflammation of the large intestine (colon). The colon is the part of the digestive system where water is removed from undigested material, and the remaining waste material is stored. The rectum is the end of the colon adjacent to the anus. In patients with ulcerative colitis, ulcers and inflammation of the inner lining of the colon lead to symptoms of abdominal pain, diarrhea, and rectal bleeding.
Ulcerative colitis is closely related to another condition of inflammation of the intestinescalled Crohn's disease. Together, they are frequently referred to as inflammatory bowel disease (IBD). Ulcerative colitis and Crohn's diseases are chronic conditions. Grohn's disease can affect any portion of the gastrointestinal tract, including all layers of the bowel wall. It may not be limited to the GI tract (affecting the liver, skin, eyes, and joints). UC only affects the lining of the colon (large bowel). Men and women are affected equally. They most commonly begin during adolescence and early adulthood, but they also can begin during childhood and later in life.
UC found worldwide, but is most common in the United States, England, and northern Europe. It is especially common in people of Jewish descent. Ulcerative colitis is rarely seen in Eastern Europe, Asia, and South America, and is rare in the black population. For unknown reasons, an increased frequency of this condition has been observed recently in developing nations.
First degree relatives of people with ulcerative colitis have an increased lifetime risk of developing the disease, but the overall risk remains small.
What causes ulcerative colitis?
The cause of ulcerative colitis is not known. To date, there has been no convincing evidence that it is caused by infection or is contagious.
Ulcerative colitis likely involves abnormal activation of the immune system in the intestines. This system is supposed to defend the body against harmful bacteria, viruses, fungi, and other foreign invaders. Normally, the immune system is activated only when the body is exposed to harmful invaders. In patients with ulcerative colitis, however, the immune system is abnormally and chronically activated in the absence of any known invader. The continued abnormal activation of the immune system causes chronic inflammation and ulceration portions of the large intestine. This susceptibility to abnormal activation of the immune system is genetically inherited. First degree relatives (brothers, sisters, children, and parents) of patients with IBD are therefore more likely to develop these diseases.
There have been multiple studies using genome wide association scans investigating genetic susceptibility in ulcerative colitis. These studies have found there to be approximately 30 genes that might increase susceptibility to ulcerative colitis including immunoglobulin receptor gene FCGR2A, 5p15, 2p16, ORMDL3, ECM1, as well as regions on chromosomes 1p36, 12q15, 7q22, 22q13, and IL23R. At this early point in the research, it is still unclear how these genetic associations will be applied to treating the disease, but they might have future implications for understanding pathogenesis and creating new treatments.
What are the symptoms of ulcerative colitis?
Common symptoms of ulcerative colitis include rectal bleeding, abdominal pain, and diarrhea, but there is a wide range of symptoms among patients with this disease. Variability of symptoms reflects differences in the extent of disease (the amount of the colon and rectum that are inflamed) and the intensity of inflammation. Generally, patients with inflammation confined to the rectum and a short segment of the colon adjacent to the rectum have milder symptoms and a better prognosis than patients with more widespread inflammation of the colon. The different types of ulcerative colitis are classified according to the location and the extent of inflammation:
- Ulcerative proctitis refers to inflammation that is limited to the rectum. In many patients with ulcerative proctitis, mild intermittent rectal bleeding may be the only symptom. Other patients with more severe rectal inflammation may, in addition, experience rectal pain, urgency (sudden feeling of having to defecate and a need to rush to the bathroom for fear of soiling), and tenesmus (ineffective, painful urge to move one's bowels caused by the inflammation).
- Proctosigmoiditis involves inflammation of the rectum and the sigmoid colon (a short segment of the colon contiguous to the rectum). Symptoms of proctosigmoiditis, like that of proctitis, include rectal bleeding, urgency, and tenesmus. Some patients with proctosigmoiditis also develop bloody diarrhea and cramps.
- Left-sided colitis involves inflammation that starts at the rectum and extends up the left colon (sigmoid colon and descending colon). Symptoms of left-sided colitis include bloody diarrhea, abdominal cramps, weight loss, and left-sided abdominal pain.
- Pancolitis or universal colitis refers to inflammation affecting the entire colon (right colon, left colon, transverse colon and the rectum). Symptoms of pancolitis include bloody diarrhea, abdominal pain and cramps, weight loss, fatigue, fever, and night sweats. Some patients with pancolitis have low-grade inflammation and mild symptoms that respond readily to medications. Generally, however, patients with pancolitis suffer more severe disease and are more difficult to treat than those with more limited forms of ulcerative colitis.
- Fulminant colitis is a rare but severe form of pancolitis. Patients with fulminant colitis are extremely ill with dehydration, severe abdominal pain, protracted diarrhea with bleeding, and even shock. They are at risk of developing toxic megacolon (marked dilatation of the colon due to severe inflammation) and colonic rupture (perforation). Patients with fulminant colitis and toxic megacolon are treated in the hospital with potent intravenous medications. Unless they respond to treatment promptly, surgical removal of the diseased colon is necessary to prevent colonic rupture.
While the intensity of colon inflammation in ulcerative colitis waxes and wanes over time, the location and the extent of disease in a patient generally stays constant. Therefore, when a patient with ulcerative proctitis develops a relapse of his or her disease, the inflammation usually is confined to the rectum. Nevertheless, a small number of patients (less than 10%) with ulcerative proctitis or proctosigmoiditis can later develop more extensive colitis. Thus, patients who initially only have ulcerative proctitis can later develop left-sided colitis or even pancolitis.