context: Ulcerative colitis ( UC) is an inflammatory bowel disease. It causes irritation, inflammation, and ulcers in the lining of your large intestine, or colon. UC is different from other diseases with similar symptoms, like Crohn's disease and irritable bowel syndrome. There's no cure, and people usually have symptom flare-ups off and on for life. But the right treatments can help you keep a handle on the disease. Ulcerative colitis happens when your immune system makes a mistake. Normally it attacks invaders in your body, like the common cold. But when you have UC, your immune system thinks food, good gut bacteria, and the cells that line your colon are the intruders. White blood cells that usually protect you attack the lining of your colon instead. They cause the inflammation and ulcers. Doctors aren't sure why people get the condition. Your genes may play a role -- the disease sometimes runs in families. Other things in the world around you may make a difference, too. So far, research hasn't discovered one clear cause for UC. Food and stress don't cause it, but they can trigger a flare of symptoms. The main symptom of ulcerative colitis is bloody diarrhea. There might be some pus in your stools, too. Other problems include: Cramping belly pain Sudden urges to empty your colon right away Not feeling hungry Weight loss Feeling tired Fever Dehydration Joint pain or soreness Canker sores Eye pain when you look at a bright light Too few red blood cells, called anemia Skin sores Feeling like you haven't completely emptied your colon after you use the bathroom Waking up at night to go Not being able to hold your stool in Your symptoms can flare up, go away, and come back. Sometimes they might not bother you for weeks or years at a time. Other gut diseases can have some of the same symptoms. Crohn's disease causes inflammation, too, but it affects other places in your digestive tract. Ulcerative colitis involves only your large intestine and its lining. Irritable bowel syndrome has some of the same symptoms as UC, but it doesn't cause inflammation or ulcers. Instead, it's a problem with the muscles in your intestines. Your doctor will use tests to tell if you have UC instead of another gut disease. Blood tests can show if you have anemia or inflammation. Stool samples can help your doctor rule out an infection or parasite in your colon. They can also show if there's blood in your stool that you can't see. Flexible sigmoidoscopy lets a doctor look at the lower part of your colon. He will put a bendable tube into your lower colon through your bottom. The tube has a small light and camera on the end. Your doctor might also use a small tool to take a piece of the lining of your lower colon. This is called a biopsy. A doctor in a lab will look at the sample under a microscope. Colonoscopy is the same process as flexible sigmoidoscopy, only your doctor will look at your whole colon, not just the lower part. X-rays are less common for diagnosing the disease, but your doctor may want you to have one in special cases. The type of ulcerative colitis you have depends on where it's located in your body: Ulcerative proctitis is usually the mildest form. It's confined to the area closest to your anus (rectum). Rectal bleeding may be the only sign of the disease. Proctosigmoiditis involves your rectum and the lower end of your colon (you may hear the doctor call it the sigmoid colon). You'll have bloody diarrhea, belly cramps and pain, and you'll have the urge to poop, but you won't be able to (the doctor will call this tenesmus). Left-sided colitis causes cramps on that side of your belly. You'll also have bloody diarrhea and you might lose weight without trying. You'll have inflammation from your rectum up through the sigmoid and descending colon. Pancolitis often affects your entire colon. It can cause severe bouts of bloody diarrhea, belly cramps and pain, fatigue, and major weight loss. Acute severe ulcerative colitis is rare. It affects the entire colon and causes severe pain, heavy diarrhea, bleeding, and fever. You won't be able to eat. UC treatment has two main goals. The first is to ease your symptoms and give your colon a chance to heal. The second is to prevent more flare-ups. You may need a mix of diet changes, medication, or surgery to reach those goals. Diet. Food doesn't cause ulcerative colitis, but some types can make your symptoms worse. You might find that soft, bland food doesn't bother you as much as spicy or high-fiber dishes. If you can't digest the sugar in milk called lactose (meaning you're lactose intolerant), your doctor may tell you to avoid dairy products. A balanced diet with plenty of fiber, lean protein, fruits, and veggies should provide enough vitamins and nutrients. Medicine. Your doctor may prescribe a few different kinds of drugs, including: Antibiotics to fight infections and let your large intestine heal Medicine to lower inflammation in your colon and control your symptoms. You may start by taking one type, called aminosalicylates. If those don't work or your symptoms are more severe, your doctor may prescribe another type of anti-inflammatory drug, a corticosteroid. Meds to help stop your immune system's attack on your colon Biologics are drugs made from proteins in living cells instead of chemicals. They are for people with severe ulcerative colitis. Surgery. If other treatments don't work or your UC is severe, you might need surgery to remove your colon. The doctor will call this a colectomy. For most people, ulcerative colitis is a chronic, or long-term condition. You'll have flares and periods with no symptoms at all (your doctor will call this remission). A small number of people have one attack and are never troubled again. If you get ulcerative proctitis, you probably won't need surgery and can live a normal life. A small number of people, about 10% of those with UC, have an initial attack and quickly get worse, with serious complications. For about 20% to 30% of people who have it, the disease spreads to the large intestine over time. This can turn into colon cancer, but about half the people who get it survive if doctors catch the disease early enough and remove their colon.