If you’re living with chronic gastrointestinal (GI) problems, you may have Crohn’s disease or ulcerative colitis (UC), two forms of inflammatory bowel disease (IBD) that together affect approximately three million Americans.

Both inflammatory conditions involve the digestive system, and people often struggle to distinguish between them.

“The most basic difference is that Crohn’s disease can involve the entire GI tract, from the mouth all the way down to the anus, whereas ulcerative colitis is restricted to the colon,” says Louis Cohen, MD, an assistant professor of gastroenterology at Icahn School of Medicine at Mount Sinai in New York City.

Read on to learn more about the subtle yet significant differences between these two diseases and how your treatment options can vary.

Crohn’s disease is an autoimmune disorder and a form of IBD that causes inflammation in the gastrointestinal tract. The inflammation can lead to lesions, such as sores and ulcers, which are most commonly found in the small intestine and large intestine, but they can occur anywhere in the digestive tract. Crohn’s disease causes a range of symptoms, including abdominal pain, diarrhea, rectal bleeding, fatigue, and weight loss. Inflammation can also lead to complications like a bowel obstruction, which may require surgery.

Because Crohn’s can occur in different parts of the digestive tract, there are several different types of the disease, categorized by the specific area of the digestive system that is affected, and whether or not there is “stricturing,” or narrowing, of the GI tract.

Types of Crohn’s disease include:

• Ileocolitis affects the end of the small intestine (terminal ileum), and the large intestine.

• Ileitis affects only the ileum.

• Gastroduodenal Crohn’s disease affects the stomach and the beginning of the small intestine (duodenum).

• Jejunoileitis affects the small intestine.

• Crohn’s (granulomatous) colitis affects the large intestine (colon).

The exact cause of Crohn’s disease remains unclear, but it is believed to be a combination of genetic, environmental, and immune system factors. Certain triggers such as diet, stress, and smoking can exacerbate symptoms of the disease.Ulcerative colitis is another form of IBD that mainly affects the large intestine (colon). Telltale symptoms of ulcerative colitis are blood in the stool with mucus, frequent diarrhea, loss of appetite, and tenesmus, or a strong urge to use the bathroom without necessarily having a bowel movement.Like Crohn’s, ulcerative colitis comes in different forms. These are named according to the part of the colon that is affected, including:

• Ulcerative proctitis, in which inflammation only affects the rectum.

• Left-sided colitis, which extends from the rectum through the sigmoid colon to the descending colon (located on the left side of the large intestine).

• Pan-ulcerative or total colitis, which affects the entire colon.

As with Crohn’s disease, we don’t know exactly what causes ulcerative colitis, but genetics and immune system malfunction both seem to play a role.

Both UC and Crohn’s are inflammatory conditions involving the digestive tract and present with similar symptoms, including diarrhea, abdominal pain, rectal bleeding, and severe weight loss in kids. Because both tend to develop in teenagers and young adults, and affect men and women equally, it can be difficult to tell which disease you have. Only a doctor can properly diagnose you, using a combination of imaging and endoscopic evaluation, and sometimes the diagnosis of Crohn’s versus UC is unclear in the beginning. If you suspect that you may have Crohn’s or ulcerative colitis, pay close attention to your symptoms, so that you can describe them to a GI specialist.People with ulcerative colitis experience continuous inflammation that only occurs in the colon, and they have a higher risk of colorectal cancer. However, Crohn’s can also involve large parts of the colon and increase the risk of colorectal cancer. People with UC may also experience rectal bleeding or blood in their stool more often than those with Crohn’s disease.Crohn’s disease usually results in healthy stretches of the intestine between inflamed areas. (These are also referred to as skip lesions.) Some common symptoms of Crohn’s include mouth sores, fistulas, ulcers, infections, and stricturing, or narrowing of the intestine.

The gold standard of IBD diagnosis is a colonoscopy, in which a small camera attached to a thin tube is inserted into the colon, allowing a doctor to see the entire colon and part of the small intestine and take biopsies. If the doctor sees that the inflammation starts at the rectum and moves continuously up the colon and then stops, this could be a sign of ulcerative colitis. If, however, the doctor sees inflammation in the digestive tract, with patches of healthy tissue interspersed with patches of inflamed tissue, this could be a sign of Crohn’s.Crohn’s sometimes creates clusters of immune cells called granulomas, whereas ulcerative colitis typically does not. Granulomas are the result of your body’s attempt to get rid of foreign material, and the cells are visible under a microscope.If the doctor suspects that the small intestine is involved in Crohn’s, they can use an imaging test, such as magnetic resonance imaging, a computed tomography scan, or a bowel ultrasound, to get a better look. If part of the upper GI tract, such as the stomach, is involved, your doctor may perform an upper endoscopy to determine where the inflammation is. Stool samples can also help doctors rule out other issues, like pathogens or bacteria.While a gastroenterologist is usually able to distinguish if a person has Crohn’s disease or ulcerative colitis, there are some cases where it is not totally clear which one is causing the inflammation. This is called indeterminate colitis and may affect around 10 percent of people with IBD.

People living with IBD often experience periods of flare-ups where symptoms are at a high, and periods of remission where symptoms may go away completely. Symptoms can be mild or severe and may gradually appear or start suddenly. Be on the lookout for the following signs:

• Abdominal pain

• Diarrhea

• Gas and bloating

• Loss of appetite

• Unexplained weight loss

• Mucus or blood in stool

• Upset stomach

Crohn’s disease and ulcerative colitis are generally treated with the same types of medication, however patients may respond differently to the same drug. The goal of treatment is to reduce the inflammation, which in turn reduces symptoms, allows your body to repair damaged tissue, and helps slow the progression of the disease.

Medications

Today, many people living with IBD take a class of drugs called biologics, which are protein-based therapies that target specific parts of the immune system that are inappropriately activated. Other classes of drugs include immunomodulators, which tamp down the immune system’s inflammatory response, corticosteroids, and aminosalicylates, the oldest class of drugs, which are used to keep the disease in remission.A newer type of drug, called Janus kinase inhibitors, or JAK inhibitors, consists of small molecule compounds that are absorbed into the bloodstream and can block multiple pathways of inflammation. “JAK inhibitors are being used most frequently in patients with moderate to severe disease that have failed other therapies,” Dr. Cohen says. “There is an active area of research considering the potential use of JAK inhibitors as first-line therapies, especially in patients with more severe disease, due to their rapid onset of action.”

Dietary Changes

Diet is another important factor in flare-ups of both diseases. While everybody is different, high-fiber vegetables like broccoli and cauliflower, uncooked produce, and unpeeled fruit are foods that people with IBD, particularly those with intestinal narrowing, have difficulty digesting. Dairy and fatty or greasy foods can also trigger symptoms in some people. The American Gastroenterological Association (AGA) recommends following a Mediterranean diet, which is rich in fruits, vegetables, whole grains, and lean proteins, unless contraindicated. The AGA also advises minimizing salt, sugar, and ultra-processed foods. Work with a dietitian to determine which foods you can safely eat and which ones you should avoid.

Surgery

Surgery presents an additional avenue for symptom relief in both Crohn’s and ulcerative colitis cases. For ulcerative colitis, procedures such as a colectomy or J-pouch surgery offer relief when medication fails. Meanwhile, in Crohn’s disease, surgery is often necessary to remove damaged sections of the intestine or repair fistulas. Though it is an effective option, research shows that surgery for IBD is declining due to medical advancements like biologics.

• Ulcerative colitis and Crohn’s disease are both inflammatory bowel diseases that affect the digestive system, but they have notable distinctions.

• Crohn’s disease can impact any part of the GI tract, while ulcerative colitis is confined to the colon.

• If you experience symptoms like diarrhea, abdominal pain, or blood in your stool, consult a gastroenterologist for an accurate diagnosis and a specialized treatment plan.