Inflammatory bowel disease (IBD) is an umbrella term for two main conditions, ulcerative colitis and Crohn's disease. Both cause inflammation in the digestive tract and are considered chronic conditions, which means they are long-term conditions. Ulcerative colitis and Crohn's disease tend to flare and calm down over time. Both are treatable with medicines.

Ulcerative colitis and Crohn's disease can look similar at first, with symptoms such as diarrhea, belly pain and fatigue. But where they occur in the intestines and how deep the inflammation goes, known as transmural involvement, are different. Those differences help explain the symptoms and help your healthcare team decide which tests to order and what treatments or surgeries might be recommended. Some of the main differences between ulcerative colitis and Crohn's disease include:

	Ulcerative colitis	Crohn's disease
Where it occurs	Ulcerative colitis is only in the large intestine, called the colon. It usually starts in the rectum and extends upward in a continuous line with no gaps.	Crohn's disease can affect any part of the digestive tract, from the mouth to the anus. It often skips areas, meaning there are often healthy areas of tissue between inflamed spots.
Transmural involvement	Inflammation that affects all layers of the bowel wall, known as transmural involvement, is not a hallmark of ulcerative colitis. In ulcerative colitis, the inflammation is limited to the mucosal layer. This is the innermost lining of the colon.	Transmural involvement is a feature of Crohn's disease. In Crohn's disease, inflammation can involve deeper layers of the intestinal wall. This can lead to narrowing of the intestine, tunnels in the tissue, known as fistulas, and pockets of infection, called abscesses.
Symptoms	Symptoms that point toward ulcerative colitis include bloody diarrhea, a sudden, urgent need to use the bathroom, and feeling like you still have to go even after a bowel movement. Because ulcerative colitis is limited to the colon and starts at the rectum, cramps and bleeding centered in the lower abdomen or rectum are common. Fatigue and fever may happen during serious flares.	Symptoms that point toward Crohn's disease include belly pain with often nonbloody diarrhea and unintended weight loss, especially when the small intestine is involved. Issues in the area around the anus, known as the perianal area, can occur. They include drainage, painful fissures and tunnels in the tissues, called fistulas. Mouth sores also suggest Crohn's disease. Narrowing in the intestines, called strictures, can cause nausea, vomiting or bloating.
Granulomas	Granulomas are clusters of immune cells that form in response to chronic inflammation. They can be seen on biopsy samples. Granulomas are not a classic feature of ulcerative colitis.	Granulomas may sometimes be found on biopsy in Crohn's disease. They're considered a supportive finding for diagnosing Crohn's disease, but they're not always present.
Malnutrition	Because the colon does not absorb nutrients and calories, malnutrition can occur in ulcerative colitis. It typically only develops if the condition is severe or lasts a long time.	Malnutrition is more common and often more severe in Crohn's disease. This is because Crohn's can affect any part of the digestive tract, including the small intestine. This is where most nutrients are absorbed. When inflammation or surgery affects this area, it can lead to malabsorption. This means the body doesn't take in enough nutrients from food. People with Crohn's may experience: Weight loss. Vitamin and mineral deficiencies. Bone loss. Anemia.
Cancer risk and screening	There is a higher risk of colon cancer with long standing, extensive ulcerative colitis. Your risk is higher if you also have a liver condition called primary sclerosing cholangitis (PSC).  The risk begins to rise 8 to 10 years after diagnosis, especially if inflammation has been ongoing. With ulcerative colitis, regular colonoscopies are recommended. People with PSC and IBD should immediately begin and continue colonoscopy exams.	People with Crohn's disease that affects the colon also have an increased risk of colon cancer. But the risk is generally lower than in ulcerative colitis. The risk is mainly present when Crohn's disease involves most of the colon and has been active for many years. Like ulcerative colitis, inflammation over time is a key factor. With Crohn's disease, colon cancer risk rises when the colon is involved. There's also a small risk of small bowel cancer if the small intestine is affected.
The role of surgery in treatment	Surgically removing the colon and rectum, known as proctocolectomy, can cure ulcerative colitis.	Surgery does not cure Crohn's disease. It can come back at the site of the operation. But surgery may be used to fix complications, such as blockages, anal fistulas or abscesses. Surgery also may be used to remove badly diseased segments of the intestine. With newer therapies, Crohn's disease can be prevented from returning.

These four conditions are often confused because they all affect the digestive system, but they're quite different in terms of cause, symptoms and treatment. Crohn's disease and ulcerative colitis are both forms of inflammatory bowel disease (IBD).

Irritable bowel syndrome (IBS) is a separate, noninflammatory condition. IBS causes symptoms such as abdominal pain, bloating and changes in bowel habits. But IBS doesn't involve damage or inflammation in the digestive tract.

Both ulcerative colitis and Crohn's disease can be serious, lifelong conditions. They each come with their own challenges. The severity of each condition depends on the person and how the disease affects the person.

Because Crohn's disease can involve more areas of the digestive system and cause complications such as fistulas, strictures and abscesses, it's often considered more complex and unpredictable in its course.

Ulcerative colitis also can be very serious. In rare cases, it can lead to life-threatening complications such as toxic megacolon, where the colon becomes severely inflamed, swollen and stretched out. Ulcerative colitis also may cause a hole in the colon, called a perforation. There is a higher risk of these complications during severe flares.

The risk of dying of either ulcerative colitis or Crohn's disease is rare. Most people with IBD live full lives with proper treatment and monitoring. That said, both conditions carry an increased risk of colorectal cancer, especially in people with long-standing, extensive disease.

You cannot have both conditions at the same time. And one doesn't lead to the other. Ulcerative colitis and Crohn's disease are considered distinct types of inflammatory bowel disease (IBD), each with its own patterns of inflammation and clinical features.

Sometimes there are situations where it's not clear which condition a person has. This may be early in the disease or when inflammation is limited to the colon. In these cases, healthcare professionals may use the term "indeterminate colitis." Indeterminate colitis means the inflammation in the colon doesn't clearly match the typical features of either ulcerative colitis or Crohn's disease.

The diagnosis may change over time as more information becomes available through biopsies, imaging or surgery.

Ulcerative colitis and Crohn's disease don't cause other conditions. But the inflammation behind them can affect areas of the body outside the digestive tract, leading to extraintestinal manifestations. These include:

• Joint pain or arthritis. This is one of the most common shared complications, especially in large joints such as the knees, hips and elbows.
• Skin conditions. People with IBD may experience skin conditions, including erythema nodosum and pyoderma gangrenosum. Erythema nodosum causes painful red bumps that usually appear on the legs. Pyoderma gangrenosum can lead to deep, ulcerating skin sores.
• Eye conditions. This is another shared issue, with conditions such as uveitis and episcleritis causing redness, discomfort and, in some cases, vision changes.
• Kidney stones. People with IBD have up to a 10% risk of having kidney stones.
• Liver conditions. Ulcerative colitis and Crohn's disease can be linked to liver conditions, most notably steatotic liver disease, formerly known as fatty liver disease, and primary sclerosing cholangitis (PSC). PSC is a chronic liver disease involving inflammation and scarring of the bile ducts. PSC is more common in people with ulcerative colitis but also can occur in people with Crohn's disease.

Ulcerative colitis vs. Crohn's disease

Yes, certain medicines can make ulcerative colitis or Crohn's disease worse or may even play a role in triggering the disease in people who are at risk. They include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs). Taking nonprescription NSAIDs, such as ibuprofen (Advil, Motrin IB, others) or naproxen sodium (Aleve, others), may trigger flares in people who already have ulcerative colitis or Crohn's disease.
• Antibiotics. Taking antibiotics has been linked to a higher risk of developing IBD, especially Crohn's disease, but it's not clear if antibiotics directly cause it. Some studies show that people who have taken antibiotics are more likely to be diagnosed with IBD than those who haven't.

If you have IBD, it's important to talk with your healthcare professional before starting any new medicine, even nonprescription medicines.

ANA is typically associated with autoimmune diseases such as lupus, not inflammatory bowel disease (IBD). Some people with IBD may have a positive ANA test, especially if they're taking certain medicines such as biologics or immunomodulators. But this is not a standard marker used to diagnose or monitor ulcerative colitis or Crohn's disease.

Yes, both Crohn's disease and ulcerative colitis are considered leukocytic conditions. In leukocytic conditions, white blood cells, also called leukocytes, are part of the disease process.

In both types of inflammatory bowel disease (IBD), the immune system becomes overactive and sends leukocytes into the lining of the digestive tract. These cells release inflammatory chemicals that damage tissues and cause symptoms such as pain, diarrhea and bleeding.

This leukocyte-driven inflammation is a hallmark of IBD and is why many treatments aim to block or calm down white blood cell activity.

No, neither ulcerative colitis nor Crohn's disease is caused by a virus. They are both types of inflammatory bowel disease (IBD). They are chronic immune-mediated conditions. The conditions happen because the immune system mistakenly attacks parts of the digestive tract, causing inflammation.

Viruses, bacteria and environmental factors may play a role in triggering IBD for some people. But ulcerative colitis and Crohn's disease are not infections and cannot be spread from person to person.

Ulcerative colitis vs. Crohn's disease

Smoking increases the risk of developing Crohn's disease and leads to a more aggressive disease course. Quitting smoking is strongly recommended if you have Crohn's disease.

Smoking does not cause ulcerative colitis and may even lower the risk of developing it. But the overall health risks of smoking far outweigh any potential protective effect for ulcerative colitis, and quitting smoking is still recommended.

Oct. 28, 2025

Original article: https://www.mayoclinic.org/diseases-conditions/inflammatory-bowel-disease/in-depth/ulcerative-colitis-vs-crohns-disease/art-20590269