Ulcerative colitis symptoms can vary, depending on the severity of inflammation and where it occurs. Signs and symptoms may include:

• Diarrhea, often with blood or pus
• Abdominal pain and cramping
• Rectal pain
• Rectal bleeding — passing small amount of blood with stool
• Urgency to defecate
• Inability to defecate despite urgency
• Weight loss
• Fatigue
• Fever
• In children, failure to grow

Most people with ulcerative colitis have mild to moderate symptoms. The course of ulcerative colitis may vary, with some people having long periods of remission.

Types

Doctors often classify ulcerative colitis according to its location. Types of ulcerative colitis include:

• Ulcerative proctitis. Inflammation is confined to the area closest to the anus (rectum), and rectal bleeding may be the only sign of the disease. This form of ulcerative colitis tends to be the mildest.
• Proctosigmoiditis. Inflammation involves the rectum and sigmoid colon (lower end of the colon). Signs and symptoms include bloody diarrhea, abdominal cramps and pain, and an inability to move the bowels in spite of the urge to do so (tenesmus).
• Left-sided colitis. Inflammation extends from the rectum up through the sigmoid and descending colon. Signs and symptoms include bloody diarrhea, abdominal cramping and pain on the left side, and unintended weight loss.
• Pancolitis. Pancolitis often affects the entire colon and causes bouts of bloody diarrhea that may be severe, abdominal cramps and pain, fatigue, and significant weight loss.
• Acute severe ulcerative colitis. This rare form of colitis affects the entire colon and causes severe pain, profuse diarrhea, bleeding, fever and inability to eat.

The exact cause of ulcerative colitis remains unknown. Previously, diet and stress were suspected, but now doctors know that these factors may aggravate but don't cause ulcerative colitis.

One possible cause is an immune system malfunction. When your immune system tries to fight off an invading virus or bacterium, an abnormal immune response causes the immune system to attack the cells in the digestive tract, too.

Heredity also seems to play a role in that ulcerative colitis is more common in people who have family members with the disease. However, most people with ulcerative colitis don't have this family history.

Ulcerative colitis affects about the same number of women and men. Risk factors may include:

• Age. Ulcerative colitis usually begins before the age of 30. But, it can occur at any age, and some people may not develop the disease until after age 60.
• Race or ethnicity. Although whites have the highest risk of the disease, it can occur in any race. If you're of Ashkenazi Jewish descent, your risk is even higher.
• Family history. You're at higher risk if you have a close relative, such as a parent, sibling or child, with the disease.

Possible complications of ulcerative colitis include:

• Severe bleeding
• A hole in the colon (perforated colon)
• Severe dehydration
• Liver disease (rare)
• Bone loss (osteoporosis)
• Inflammation of your skin, joints and eyes
• An increased risk of colon cancer
• A rapidly swelling colon (toxic megacolon)
• Increased risk of blood clots in veins and arteries