Ulcerative Colitis vs. Crohn’s Disease - what's the difference?

Inflammatory bowel disease (IBD) is an umbrella term that primarily covers two chronic conditions affecting a person’s digestive tract: ulcerative colitis and Crohn’s disease. While they share many similarities, they also have distinct differences that impact diagnosis, treatment, and daily life. If you or someone you love is learning to navigate an IBD diagnosis, understanding these differences may help you feel more informed.

What Is IBD anyways?

For starters, IBD is not the same as IBS (which stands for irritable bowel syndrome). They sound similar, but IBS affects bowel function, while, as the same suggests, IBD involves chronic inflammation of the gastrointestinal (GI) tract due to an abnormal immune response. In people with IBD, the immune system mistakenly attacks healthy tissue in the digestive tract, leading to symptoms like abdominal pain, diarrhea, fatigue, and weight loss. IBS may have similar signs and symptoms, but is commonly caused by stress, nervous system changes, usage of antibiotics, or other changes in the gut.

Under the IBD umbrella, ulcerative colitis (UC) and Crohn’s disease differ in several ways:

Location of Inflammation

UC affects only the colon and rectum, and the inflammation is continuous. Crohn’s disease, on the other hand, can affect any part of the GI tract, from the mouth to the anus. The inflammation of Crohn’s tends to be patchy in nature with sections of healthy tissue in between the inflamed areas.

Inflammation depth

In UC, inflammation is limited to the innermost lining of the colon. Crohn’s disease affects all layers of the bowel wall, which can lead to complications like strictures (narrowing of the intestines) and fistulas (abnormal connections between organs).

Pattern of disease

UC typically presents with a predictable pattern, starting in the rectum and extending upward. This is why some UC medicines are designed to be administered rectally, for closer targeting of inflammation. Crohn’s disease is more variable, with inflammation that can skip areas and appear in multiple parts of the GI tract.

Shared experiences

Despite their differences, UC and Crohn’s disease share many symptoms:

• Abdominal pain and cramping
• Diarrhea (sometimes bloody)
• Fatigue
• Weight loss
• Urgent need to use the bathroom
• Anemia due to blood loss or poor nutrient absorption

Symptoms can come and go, with flare-up periods followed by spans of remission. Since both conditions are auto-immune in nature they can also affect other parts of the body, leading to joint pain, skin issues, and eye inflammation.

Getting a diagnosis

Both UC and Crohn’s disease are most commonly diagnosed in teenagers and young adults, though they can occur at any age. Having a family history of IBD increases an individual’s risk as does some modifiable factors such as smoking and high intake of processed foods.

Frequently the process of diagnosing IBD can be complex as there is no single test that confirms UC or Crohn’s disease. Instead, doctors must try and solve “the puzzle” using a combination of:

• Medical history and physical exam
• Blood tests to check for inflammation, anemia, or infection
• Stool tests to rule out infections
• Endoscopic procedures, such as colonoscopy or sigmoidoscopy, to view the colon and collect tissue samples
• Imaging tests, like CT or MRI scans, to assess inflammation and rule out complications

Even with testing, it may occasionally difficult to distinguish between UC and Crohn’s. In a small percentage of cases, patients are diagnosed with what is called indeterminate colitis, where features of both conditions are present.

Whether you’re newly diagnosed or supporting someone with IBD, becoming educated on the condition is a first step towards setting expectations and managing for better quality of life. For people quietly living with ongoing digestive issues, it is important to talk to a doctor about the timing, severity, and potential triggers of any pain or episodes. It may feel uncomfortable but is the only way to get answers and feel better again. Even if the diagnosis is IBD, there are many newer treatment approaches that can help someone feel more at ease and in control