Crohn’s disease and ulcerative colitis are two forms of inflammatory bowel disease (IBD). This means that they cause the gut to become inflamed. Many symptoms of these conditions affect a person’s gut, but they can also affect other parts of the body. There is also a subset of Crohn’s disease called Crohn’s colitis, which only affects the colon.

As one 2020 article notes, IBD mostly develops in people aged 15–30 years, and it is most common in industrialized and colder countries.

This article will provide information about IBD. It will also discuss what scientists have to say about the symptoms, causes, diagnosis, treatment, and outlook associated with Crohn’s disease and ulcerative colitis.

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IBD occurs when someone’s intestinal tract, which includes their large and small intestines, regularly becomes inflamed. This inflammation comes in bouts.

There are several types of IBD, including:

  • Crohn’s disease: Crohn’s disease is a chronic illness that causes inflammation of the gut. It can affect any part of the gastrointestinal tract, including a person’s mouth or anus. A person may experience symptoms throughout their body. The Crohn’s and Colitis Foundation says that this condition affects around 3 million people in the United States.
  • Crohn’s colitis: In Crohn’s colitis, the condition only affects the colon. However, people with this subset are more likely to experience skin lesions or joint pain than people with other types of Crohn’s disease, according to the Crohn’s and Colitis Foundation.
  • Ulcerative colitis: This condition only affects the inner lining of the colon. Unlike in Crohn’s disease, it does not “skip” parts of the colon, so no part of the colon remains unaffected.

Symptoms of Crohn’s disease can affect different parts of a person’s body.

In the gut

Gastrointestinal symptoms of Crohn’s disease can include:

  • continued diarrhea
  • bleeding from the rectum
  • an urgent need to pass stool
  • abdominal cramps or pain
  • a feeling that there is more stool to pass
  • constipation

In other parts of the body

Symptoms of Crohn’s disease that affect other parts of the body can include:

  • flushed skin around the eyes, eye pain, or vision changes
  • mouth sores
  • swelling and pain in the joints
  • bumps, sores, or rashes on the skin
  • fever
  • loss of appetite
  • unexplained weight loss
  • fatigue
  • night sweats
  • changes in the menstrual cycle
  • osteoporosis
  • kidney stones
  • liver complications, such as primary sclerosing cholangitis and cirrhosis

Crohn’s disease and ulcerative colitis have many similarities and differences regarding the symptoms a person may experience.

Similar symptoms

Some of the main symptoms of IBD are common to both Crohn’s disease and ulcerative colitis. These include:

Symptoms of Crohn’s disease

One 2020 article lists the following symptoms of Crohn’s disease:

  • abdominal pain
  • bloating and flatulence
  • diarrhea
  • unexplained weight loss
  • anemia
  • anorexia
  • difficulty absorbing nutrients from food
  • perianal abscesses
  • cutaneous fistulas, wherein the contents of the intestine leak through the skin

Symptoms of ulcerative colitis

A different 2020 article lists the following symptoms of ulcerative colitis:

  • diarrhea with mucus or blood
  • cramping rectal pain, or tenesmus
  • the urgency to pass stool
  • malaise
  • abdominal pain
  • unexplained weight loss
  • fever

Ulcerative colitis symptoms may come on gradually, and they may come and go.

Complications arising from Crohn’s disease and ulcerative colitis may only affect the intestines, but people might also experience them in other parts of the body.

In the intestines

According to the Crohn’s and Colitis Foundation, intestinal complications of Crohn’s disease may include:

  • Intestinal obstruction: The most common complication of Crohn’s disease occurs when the damage in the bowel causes scar tissue, which narrows the bowel wall or intestinal passage. Doctors also call these strictures.
  • Abscesses: Pockets of pus may form in the intestinal wall after bacterial infections. Symptoms of this complication can include swelling, tenderness, pain, and fever, and treatment involves lancing the abscess or taking antibiotics.
  • Fistulas: Ulcers in the intestinal tract may become deeper and turn into tunnels, or fistulas, that connect different parts of the intestine, bladder, vagina, or skin. They affect around 30% of people with Crohn’s disease and can become infected, requiring antibiotics or surgery.
  • Fissures: A person with Crohn’s disease may experience cracks or tears in the lining of the anus.
  • Malnutrition: Since Crohn’s disease affects the small intestine, some people with a severe case of the condition may find that their body is not absorbing nutrients the way it should.

The Crohn’s and Colitis Foundation adds that intestinal complications of ulcerative colitis can include:

  • Perforation of the bowel: Ongoing inflammation in the intestine can cause it to weaken, which can increase the risk of developing holes in the bowel. If the contents of the intestine spill into the abdomen, this could lead to serious complications.
  • Fulminant colitis: In under 10% of people with ulcerative colitis, the entire intestinal wall becomes damaged, and the colon dilates. This can cause muscle loss and expansion in the colon, and gas may become trapped in the intestine.
  • Toxic megacolon: If the colon dilates, it can no longer push intestinal gas, and the intestine could rupture, potentially leading to death. However, toxic megacolon tends to be rare, and prompt treatment significantly lowers the risk of mortality.
  • Colorectal cancer: Around 5–8% of people with ulcerative colitis develop colorectal cancer within 20 years of receiving their diagnosis. This means that they are 2% more likely to develop it than the general population.

In other parts of the body

According to the Crohn’s and Colitis Foundation, other parts of the body that complications of Crohn’s disease and ulcerative colitis can affect include:

  • Joints: Up to 30% of people with Crohn’s disease or ulcerative colitis experience arthritis, or swelling of the joints. Examples include peripheral arthritis, axial arthritis, and ankylosing spondyloarthritis.
  • Skin: Around 20% of those with Crohn’s disease or ulcerative colitis experience complications that involve the skin, including flushed skin, bumps, sores, skin tags, and ulcers.
  • Bones: Among people with IBD, 30–60% have low bone density. This can lead to conditions such as osteoporosis.
  • Eyes: Roughly 10% of people with Crohn’s disease or ulcerative colitis experience complications involving the eyes, such as dry eyes or inflammation.
  • Kidneys: The more serious the kidney condition, the rarer it is as a complication of IBD. However, people may experience kidney stones, inflamed kidneys, or obstructions in the kidneys.
  • Liver: Conditions of the liver can affect 5% of people with IBD. These conditions may include fatty liver disease, hepatitis, or gallstones.
  • Blood: Around 1 in 3 people with IBD have a low red blood cell count. This can lead to anemia.

Learn more about Crohn’s disease and joint pain here.

IBD occurs when a person’s immune system reacts inappropriately to their intestinal flora, which is the community of bacteria that live in their intestine.

Scientists are still conducting research to find out the exact cause of this condition.

IBD may occur as a result of a person’s immune system damaging the intestinal tract. This can be due to a number of different factors, including inappropriate interactions with the person’s intestinal flora.

Also, people’s dietary and behavioral habits may worsen their condition. For example, people should try to avoid smoking if they have Crohn’s disease.

As one 2020 article explains, scientists do not know what causes the immune system to react in this way. However, there does seem to be a genetic component, which means that some people may be predisposed to develop IBD.

Around 5–20% of people with Crohn’s disease have a close relative with IBD. This could be a parent, child, or sibling. The genetic link seems to be stronger in people with Crohn’s disease than in those with ulcerative colitis.

Learn more about the different types and causes of IBD here.

Taking a medical history and conducting a physical exam can help doctors diagnose IBD.

Doctors also use a variety of other diagnostic tests to detect IBD. These include:

  • Endoscopy: Endoscopies involve doctors inserting a special camera-containing tube into a person’s body. Endoscopies allow doctors to look inside a person’s intestinal tract for signs of IBD. A doctor may also recommend a capsule endoscopy. This involves a person swallowing a small camera, which takes pictures of parts of the small intestine that endoscopes do not usually reach.
  • Biopsy: Doctors also use biopsies to test for ulcerative colitis. These involve removing small amounts of a person’s intestinal tract in order to test it for signs of this condition.
  • Stool examination: Stool examinations are also important to the diagnostic process, as they can help doctors rule out certain colonic infections. These can share symptoms with IBD.
  • Imaging scans: CT or MRI scans are helpful for detecting abscesses and fistulas.
  • Blood tests: Because Crohn’s disease and ulcerative colitis have similar effects, scientists estimate that in at least 10% of cases, doctors cannot initially tell these conditions apart. However, doctors can use certain blood tests to make a diagnosis of Crohn’s disease.

IBD requires different sorts of treatment depending on the severity of the condition.

The goal of treatment is to control and prevent inflammation. Some typical treatment options for both Crohn’s disease and ulcerative colitis include:

  • medications to reduce existing inflammation, such as corticosteroids
  • medications to prevent inflammation
  • surgery to remove parts of the intestinal tract

Medications to reduce and prevent inflammation may overlap. For example, a person could take steroids to control ongoing inflammation and take an immunomodulator to prevent its recurrence.

Surgery tends to come in the later stages of IBD, though doctors may sometimes recommend earlier surgeries if medication is not working or there are complications.

Learn more about the different treatment options for Crohn’s disease here.

Crohn’s disease and ulcerative colitis are both lifelong conditions for which there is no known cure. Doctors focus treatment on helping people manage their symptoms.

As one 2020 article explains, people with ulcerative colitis have the same life expectancy as those in the general population. However, a different 2020 article notes that people with Crohn’s disease have a slightly reduced life expectancy than average.

Receiving a diagnosis of Crohn’s disease or ulcerative colitis can be difficult to come to terms with. People with one of these conditions may benefit from making use of mental health resources available to them.

Learn more about different mental health resources available here.

IBD remains an area of active research.

Since both conditions can have quite an impact on a person’s quality of life, early diagnosis and treatment are always best.

Anyone with symptoms of Crohn’s disease or ulcerative colitis should seek a doctor’s advice as soon as possible.