Crohn’s disease is a chronic condition that causes the digestive tract to become inflamed. The type of Crohn’s disease depends on where in the gastrointestinal tract it is inflamed. Pathology is the branch of medical science that studies and diagnoses diseases based on examination of tissues and body fluids. It looks at the causes and effects, as technology has advanced the molecular background of this condition.

Crohn’s disease is a type of inflammatory bowel disease (IBD). IBD affects around 1.3% of adults in the United States.

Crohn’s disease causes inflammation and irritation in the bowel, involving the entire thickness of the bowel lining. It most commonly affects the small intestine and the beginning of the large intestine and can have areas of skip lesions that are not affected. However, it can also affect any part of the digestive tract from the mouth to the anus.

Doctors are not sure exactly what causes Crohn’s disease. However, they believe it to be an autoimmune disease that can occur due to a combination of hereditary, genetic, and environmental factors. Diet and stress may worsen the condition, but they do not cause it.

In this article, we discuss the pathology of Crohn’s disease and the differences between the different types of the disease.

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When discussing pathology, doctors give a “gross” description and a “microscopic” description. The gross description describes aspects of the disease that are visible without a microscope.

In Crohn’s disease, doctors may notice the following pathology:

Gross description. Inflammation causes the outer lining of the intestinal wall to thicken as well as the internal lining. Those changes result in a less functional, noncompliant, stiffer bowel.
Microscopic description. The internal lining becomes damaged due to inflammation and the mucosal lining can have noncaseating granulomas and inflammation of the glands, known as cryptitis.

Symptoms of Crohn’s disease may vary according to which part of the bowel is affected, but can include:

Extraintestinal symptoms

Sometimes people with Crohn’s disease can experience symptoms outside of the gastrointestinal tract. These can include:

Different types of Crohn’s disease affect different parts of the bowel. They can include:


Ileocolitis is the most common form of Crohn’s disease, affecting around 40% of people with the condition. It affects the end of the small intestine, which is known as the terminal ileum, and the large intestine, known as the colon.

Ileocolitis causes inflammation in these areas which can cause a number of symptoms to develop.


Ileitis is similar to ileocolitis, but it only affects the ileum, which is the final part of the small intestine.

In more severe cases, a person may experience complications. These can include fistulas or abscess.

A fistula forms when inflammation causes sores or ulcers to develop. These sores or ulcers can then extend through the bowel wall which can create a tunnel that drains pus from the infected area. This causes a passageway to develop between two organs or vessels that do not usually connect.

Gastroduodenal Crohn’s disease

Gastroduodenal Crohn’s disease causes inflammation in a person’s stomach and at the beginning of their small intestine, which is called the duodenum.

This is a rare form of Crohn’s disease, with one study stating that it occurs in 0.5–4% of people with Crohn’s disease.

The study adds that isolated inflammation only in the stomach and duodenum, which is just below the stomach, accounts for just 0.07% of all gastrointestinal Crohn’s disease.

Although it is rare, a person can experience this type alongside other forms of Crohn’s disease.


Jejunoileitis is a type of Crohn’s disease that causes patchy areas of inflammation in the upper half of a person’s small intestine. This area is called the jejunum. Children and young people may experience more complications in this part of the bowel than adults with the condition.

Jejunoileitis is a relatively rare form of Crohn’s disease.

Crohn’s colitis

Crohn’s colitis is a type of Crohn’s disease that only affects the colon. It causes inflammation in the colon, which causes a number of symptoms to arise.

Both skin lesions and joint pain are more common in this type of Crohn’s disease than in any other type.

Oral Crohn’s

Sometimes, Crohn’s disease can affect the mouth. This is rare, but more common in children and young people than adults.

This type of Crohn’s disease can cause mouth fissures and swelling in the lips. It can occur with other types of Crohn’s disease.

People with other types of Crohn’s disease can also experience mouth ulcers. This may be because they have a deficiency in the following nutrients:

Learn more about how Crohn’s can cause mouth ulcers here.

Perianal Crohn’s

Crohn’s can affect the skin near the anus. This may occur alone or alongside inflammation in other parts of the body.

A person whose Crohn’s is affecting the perianal area may notice:

Crohn’s disease sometimes begins with mild symptoms that can gradually get worse over time due to damage in the gut. However, severity can come and go in waves, known as flares.

The earlier a person receives a diagnosis and begins treatment, the more likely they are to reduce their risk of developing more severe symptoms.

If a person only has mild to moderate symptoms, they may be able to avoid complications. They may also be able to move, eat, and drink normally, with the disease not having a large impact on their quality of life.

More severe symptoms of Crohn’s disease can be debilitating and can have a large impact on a person’s quality of life. This can include being in constant pain or discomfort, and having a higher risk of complications such as internal bleeding, perforation of the gastrointestinal tract, and some types of bowel cancer.


Severe symptoms or complications can include:

  • Strictures. A narrow section of the bowel can form due to scar tissue from Crohn’s. Symptoms of strictures can include severe cramping abdominal pain, nausea, vomiting, and constipation. A doctor can treat strictures with medication or surgery.
  • Perforations. This rare but serious complication means a hole has formed in the bowel. It can cause severe abdominal pain, fever, nausea and vomiting.
  • Fistulas. Having a fistula means a thin passageway has formed between the gut and the skin or another organ. They may affect the loops of the bowel, bladder, vagina, and perianal skin.
  • Malabsorption. The body may not absorb nutrients properly, possibly leading to malnutrition.
  • Cancer. People with Crohn’s disease may have a higher risk of cancer, for example adenocarcinoma of the ileum.

Learn about the more serious possible complications of Crohn’s disease here.

Crohn’s disease is a chronic condition, which means it can affect a person for their whole life. Treatment can reduce symptoms, but there is no cure.

Symptoms of Crohn’s disease often appear in flares. Between these flares, a person may experience periods of time with no symptoms at all. This is known as remission.

Some people are able to experience long periods of remission that can last a number of years. However, there are usually recurrences of the disease at some point.

It is not possible for a person to predict how long their periods of remission will be.

Learn more about Crohn’s flares here.

Crohn’s disease and ulcerative colitis are both types of IBD.

Crohn’s disease can affect any part of a person’s digestive tract. This includes the esophagus, stomach, small intestine, and large intestine. However, ulcerative colitis only affects the colon.

Crohn’s disease also affects the entire thickness of the intestinal wall, while ulcerative colitis tends to only affect the top layer.

Finally, if a person has Crohn’s disease, their colon may have healthy sections in between the areas that are inflamed. Whereas a person with ulcerative colitis tends to have continuous inflammation of the colon.

Learn more about the differences between Crohn’s disease and ulcerative colitis.

Common treatments for Crohn’s disease include:

  • Medications. Medications for Crohn’s disease include immunosuppressant drugs, steroids, and biologics.
  • Surgery. In more severe cases and when medications fail to work, a person may require surgery. This may include removing diseased sections of the gastrointestinal tract. Around two-thirds to three-quarters of people with Crohn’s disease will require surgery at some point in their lives.
  • Dietary changes. A medical professional may also advise a person to make some changes to their diet. This can include avoiding foods that trigger symptoms, replacing nutrients lost during diarrhea, and ensuring that they maintain good nutrition.
  • Behavioral changes. A person may want to quit smoking as that is something which can worsen symptoms of Crohn’s disease. They may also wish to try relaxation practices including meditation, mindfulness, or yoga. Therapy and mental health support may also be effective.

Learn more about Crohn’s disease and diet here.

Crohn’s disease is a form of inflammatory bowel disease. It causes inflammation in any part of a person’s digestive tract. Common symptoms of Crohn’s disease include diarrhea, stomach cramps, abdominal pain, weight loss, and fatigue.

There are several types of Crohn’s disease that all affect different areas of the digestive tract. Each type also causes a variety of different symptoms to develop.

Types of Crohn’s disease include ileocolitis, ileitis, gastroduodenal Crohn’s disease, jejunoileitis, and Crohn’s colitis.

A person may receive treatment in the form of medication or surgery, and doctors may also suggest they make dietary or lifestyle changes to help ease symptoms.