Nearly 1 in 100 Americans experience inflammatory bowel disease (IBD), according to the Crohn's & Colitis Foundation. Crohn's disease is one of the most-common forms of IBD. We're taking a look at Crohn's disease, including symptoms and when you should seek help.

What is Crohn's disease?

Crohn's disease is a chronic, lifelong, condition that causes gastrointestinal (GI) tract inflammation.

"Crohn's disease is a condition in which individuals who are genetically susceptible develop inflammation in the gastrointestinal tract anywhere from the mouth to the anus," says Dr. Kerri Glassner, a gastroenterologist with Houston Methodist. "Crohn's disease can affect the colon, the small intestine, both the small intestine and colon, or even the perianal area, esophagus, stomach and mouth."

The chronic inflammation from Crohn's disease can cause strictures, a narrowing or blockage in the intestines called stricturing disease. Crohn's can also cause abnormal connections from the bowel to another area, such as skin, bladder, vagina or another portion of the bowel, called fistulas or fistulizing disease. Crohn's that doesn't have strictures or fistula is referred to as inflammatory disease.

Crohn's disease symptoms

A person with Crohn's disease doesn't experience the same symptoms all the time. There will be periods of no symptoms (remission) and periods with symptoms called flares. People can go weeks, months or even years without experiencing a flare, also sometimes called a flare-up. It's hard to predict when a person will experience symptoms, or why.

"A Crohn's flare-up may be experienced differently by each specific person depending upon the location of their inflammation and whether or not they have fistulizing, stricturing or inflammatory disease," Dr. Glassner says.

Symptoms can include:

• Diarrhea
• Abdominal pain
• Fever
• Blood in the stool
• Fatigue
• Feeling bloated
• Loss of appetite
• Mouth sores
• Vomiting
• Urgency to move bowels
• Weight loss

"Symptoms of Crohn's vary based on the type," Dr. Glassner says. "For example, with stricturing Crohn's disease, symptoms of obstruction such as abdominal pain and bloating, nausea, vomiting after eating can occur. Those with inflammatory disease affecting the rectum and colon may have bloody stool, urgency and diarrhea."

For people living with Crohn's disease, it's possible to have symptoms or conditions that happen outside of the GI tract, called extraintestinal manifestations. Dr. Glassner says the most common of these include skin conditions, joint pains caused by inflammation and ulcers in the mouth.

Types of Crohn's disease

Crohn's disease has various subtypes named after the affected areas of the GI tract. Ileocolitis, which affects both the small intestine (ileum) and large intestine (colon), is the most common. Other types include:

• Ileal: Swelling and inflammation develop in the small intestine
• Upper gastrointestinal: Inflammation affects the stomach and the upper small intestine
• Colonic: Inflammation affects the large intestine only

What causes Crohn's disease?

What causes Crohn's disease can't be pinned down to a single issue. There may be a genetic component — about 15% of people with Crohn's have a first-degree relative, whether a parent or sibling, that has the condition — but that's only a partial explanation.

"Just being genetically susceptible is not enough," Dr. Glassner says. "Environmental factors including diet, antibiotic exposure and other toxins such as smoking can lead to changes in the way the immune system and microbes that live in the gut interact."

Autoimmune conditions, where the immune system's defenses attack healthy cells in your GI tract, may play a factor. In addition, habits such as smoking can almost double a person's chances of developing Crohn's disease.

Tests for Crohn's disease diagnosis

Typically, Dr. Glassner says patients will make an appointment with a gastroenterologist when they are having symptoms such as diarrhea, need to use the restroom urgently, blood in the stool, abdominal pain and weight loss.

To be diagnosed with Crohn's disease, your gastroenterologist will need to perform tests: a colonoscopy or an upper endoscopy with biopsy. Other tests can also be helpful in diagnosing Crohn's, including:

• Fecal calprotectin, a stool test that evaluates for inflammation
• MRI/CT enterography
• Bowel ultrasound and video capsule endoscopy

"Tissue obtained via colonoscopy, small bowel enteroscopy or upper endoscopy is necessary to establish the diagnosis," Dr. Glassner says. "IBD serologic testing can be helpful in predicting a more aggressive disease course but should never be relied on to make a diagnosis of IBD."

Treatments for Crohn's disease

"Thankfully, there are numerous options available for the treatment of Crohn's disease," Dr. Glassner says. "This is in stark contrast to just a few years ago when we had only limited options for treatment."

Treatments for Crohn's disease can vary from periods of bowel rest up to surgery. Your gastroenterologist will suggest treatments based on affected areas of the GI tract and the person's current condition.

Treatments can include:

• Immune modulators, such as azathioprine or 6-MP — medicines that can lower inflammation by suppressing an overactive immune system.
• Biologic medications, such as infliximab, adalimumab, certolizumab, vedolizumab, ustekinumab and rizankizumab — medicines that use monoclonal antibodies to suppress the immune response.

New, promising treatments continue to enter the market for Crohn's disease.

"The small molecule upadacitinib was just approved in [May 2023]," Dr. Glassner says. "These medications work by modulating the immune system to help decrease inflammation. So far, studies on probiotics for Crohn's have not been promising, but there are studies investigating medications that specifically target the changes in the microbiome."

In addition to any treatment, Dr. Glassner emphasizes that it's very important for people with Crohn's or other types of IBD, including ulcerative colitis, to work on their overall health. That includes diet, exercise, stress management, and getting enough sleep.

"There is data to suggest that a Mediterranean type of diet is beneficial," Dr. Glassner says. "Other diets, such as the Crohn's Disease Exclusion Diet and the Simple Carbohydrate Diet, have also shown promise but are more restrictive. It is also important to continue maintenance medications and keep regular follow-ups with a gastroenterologist."

When to see your doctor

Talk with your primary care provider if you experience blood in your stool or any of the other symptoms of Crohn's disease to get evaluated. Getting a diagnosis means you can begin treatment sooner, which can bring relief. Plus, letting Crohn's progress without treatment can cause complications over time.

"If left untreated, Crohn's can lead to an increased risk of colorectal and small bowel cancer, risk for surgery and bowel resections, hospitalization and infections," Dr. Glassner says.