DEAR DOCTOR K: I’ve recently been diagnosed with ulcerative colitis. What causes it, and how is it treated?

DEAR READER: Ulcerative colitis is an inflammatory disease of the colon. (The colon is also called the large intestine.) UC can cause debilitating abdominal pain and diarrhea, and it substantially increases your risk of colon cancer.

Our large intestines contain trillions of bacteria. Normally, tissue lining the intestine prevents these bacteria from infecting the intestinal wall. But when the intestine’s lining fails, bacteria that usually are harmless can activate your immune system.

UC is an autoimmune disease. In such diseases, the immune system – which is there to defend us against foreign invaders – instead attacks our own tissues. In the case of UC, the immune system mistakenly attacks the intestine, causing inflammation and injury. Over time, UC wears away the lining of the rectum and colon; it leaves ulcers that may bleed or ooze mucus or pus.

UC can cause abdominal cramping, bloody diarrhea and urgent bowel movements. You may be able to ease your symptoms by avoiding foods that trigger your symptoms. Common culprits include spicy foods and dairy products.

Medications can often control symptoms. Most patients begin with anti-inflammatory drugs that are related to aspirin. These drugs take time to work; you may need to take them for several weeks before you are symptom-free.

If these drugs don’t work, you may be prescribed more powerful anti-inflammatory drugs: corticosteroids. Unfortunately, they can have worrisome side effects, including increased risk of infection.

In the past decade, powerful new medicines called “biologics” have been developed. They often are successful when other treatments for UC have failed, but they can also have serious side effects.

When drugs don’t work or are too difficult to tolerate, your doctor may suggest surgery to remove the colon. Surgery is also an option if your risk of colon cancer is particularly high.