What is ulcerative colitis?

Ulcerative colitis¹ (UC) is a subtype of inflammatory bowel disease (IBD) that causes inflammation and damage to the colon and rectum.

Ulcerative colitis is known for its symptoms coming and going in a “flare-like” manner. Flares² (also called flare-ups) can last for variable amounts of time, from days to weeks. Periods of time in between flares, also known as remission, can last anywhere from months to years.

There are several types of ulcerative colitis, classified by their locations in the colon and rectum:

• Ulcerative proctitis: A very mild form of UC that affects the rectum and can cause rectal bleeding.
• Proctosigmoiditis: A form of UC that affects the rectum and lower portion of the colon (known as the sigmoid colon).
• Left-sided colitis: Affects the rectum, sigmoid colon, and descending colon. People with this form of colitis may experience unintended weight loss.
• Pancolitis: A severe form of UC that affects the entirety of the colon.
• Acute severe ulcerative colitis: The rarest form of UC that affects the entirety of the colon and causes severe, sometimes life-threatening symptoms.

UC can cause severe symptoms that affect a person’s daily life, and, in some cases, can lead to complications that may become life-threatening. While UC cannot be cured, healthcare providers can manage the symptoms of the condition through medications, diet changes, and, in some cases, surgical procedures.

Crohn’s disease vs. ulcerative colitis

Ulcerative colitis and Crohn’s disease are two subtypes of inflammatory bowel disease (IBD)³. The conditions differ primarily in the areas they affect within the gastrointestinal (GI) tract.

Ulcerative colitis typically affects only the colon, rectum, and inner lining of the large intestine. Crohn’s disease can affect the entire gastrointestinal system, all the way from the mouth to the anus. Crohn’s is also known to affect all layers of the intestinal wall.

How common is ulcerative colitis?

Ulcerative colitis affects about 70 to 150 people per 100,000⁴ (0.07–0.15% of people) in the United States.

While a person may be diagnosed with UC at any point in their life, diagnosis most commonly occurs after the age of 30⁵. Men and women are diagnosed with the condition at equal rates.

The risk of developing UC increases if one has a first-degree relative who also has UC (or another form of inflammatory bowel disease). People of Ashkenazi Jewish descent also tend to have a higher risk of developing UC compared to other racial or ethnic groups.

Ulcerative colitis causes

The causes⁶ of ulcerative colitis, while not fully understood by researchers, are thought to be multifactorial. Scientists have suggested that UC may be caused⁷ by an immune response mounted by the body in reaction to a viral or bacterial infection in the colon.

In typical immune responses, the body triggers inflammatory processes to fight off foreign bodies. After the infection has been cleared, the inflammation subsides.

For people with ulcerative colitis, the inflammatory processes continue even after the infection has cleared. White blood cells can then flood the intestinal lining, causing long-lasting inflammation and ulcers.

Risk factors for ulcerative colitis

Some factors⁸ may increase your risk of developing ulcerative colitis, including:

• Age: Most people diagnosed with ulcerative colitis receive their diagnosis before the age of 30. In some cases, however, people may not show symptoms of or be diagnosed with the disease until after the age of 60.
• Race and ethnicity: People of Ashkenazi Jewish descent have the highest risk of developing ulcerative colitis when compared to other ethnic groups. Caucasians, in general, tend to develop UC more commonly than other races.
• Family history: Having a blood relative who has UC—particularly a close relative, such as a parent or sibling—can increase your risk of developing UC.

Ulcerative colitis symptoms

Symptoms of ulcerative colitis can differ from person to person. In addition, not all people with UC experience the same level of symptom severity. An estimated 50% of people with UC experience only mild symptoms of the condition.

Common signs and symptoms⁹ of ulcerative colitis include¹⁰:

• Abdominal cramping
• Abdominal pain
• Loose bowel or urgent bowel movements
• Blood in the stool
• Recurring episodes of diarrhea (loose, watery stools) that include abdominal pain and bloody stool
• Rectal pain
• Unintended weight loss
• Fatigue
• Fever

Ulcerative colitis is characterized by its symptoms arising during episodes known as flares. Some people with UC have flares every few months, while others may go years without experiencing a symptomatic UC episode.

The period of time between flares is known as remission. Flares tend to be unpredictable in both frequency and duration, meaning it may sometimes be difficult for healthcare providers to determine which treatments are the most effective for long-term symptom management.

Complications from ulcerative colitis

Complications¹¹ from ulcerative colitis can occur either in and around the intestinal system (local) or in other organs not associated with the gastrointestinal system (systemic).

Some potential complications from UC include¹²:

• Bowel perforation or rupture: Chronic inflammation of the bowel can lead to weakening of the intestinal wall. If the intestinal wall bursts (perforates), bacteria can fill the abdominal cavity and lead to peritonitis, or infection of the peritoneal cavity.
• Fulminant colitis: Fulminant colitis, which occurs in less than 10% of UC cases, involves inflammation and damage of the intestinal wall and colon.
• Toxic megacolon: In rare cases, UC can cause inflammation that results in gas becoming trapped in the colon. The colon then becomes swollen due to gas pressure, which can lead to rupture and subsequent sepsis (blood infection), which can be very dangerous or fatal.
• Primary sclerosing cholangitis (PSC): PSC, a progressive disease of the gallbladder and liver, occurs rarely in people with UC as the result of inflammation and subsequent damage of the bile ducts.
• Colorectal cancer: Between 5–8% of people with ulcerative colitis subsequently develop colorectal cancer. The more severe a person’s cases of ulcerative colitis is, the more likely it is that their condition will progress to colorectal cancer.
• Severe bleeding: Inflammation of the bowels and intestinal walls may cause bleeding. In some cases, tissue perforation can cause severe bleeding.
• Dehydration: Ulcerative colitis can lead to diarrhea. During flares, a person may be at risk of becoming dehydrated if they lose too many fluids to diarrhea.
• Osteoporosis: People who have UC are at an increased risk of having weakened bones as a result of the corticosteroids that are typically prescribed to manage the condition.
• Liver disease: Some people with ulcerative colitis develop liver diseases, the most common of which is fatty liver disease¹³ (hepatic steatosis). This condition occurs when excess fat is deposited in the liver, leaving less room for liver cells themselves.

• Joint, eye, or skin inflammation: UC has been associated with serious eye conditions¹⁴ (such as corneal disease and scleritis [inflammation of the sclera]), skin conditions¹⁵ (such as erythema nodosum and pyoderma gangrenosum), and joint inflammation (which manifests as various forms of arthritis).

• Blood clots: People with UC are said to have a nearly three times greater risk of developing a blood clot¹⁶ (thrombosis) compared to those without inflammatory bowel disease. Researchers do not know the exact cause for this but believe it is related to genetic factors.