GI Tract Guide

The esophagus transports food from the mouth, through the throat, and into the stomach.

It is rare for Crohn's disease to affect the esophagus.

A fungal infection called “thrush” can develop in the esophagus, especially after antibiotics or corticosteroid use.

Symptoms of thrush may include: pain or difficulty with swallowing, and sores on the mouth, tongue, or throat.

The stomach’s main function is digestion (breaking down food, which occurs through muscle contractions and the secretion of acid and digestive enzymes).

It is rare for Crohn's disease to affect the stomach.

Gastritis (inflammation of the stomach) can occur for several reasons, including as a result of medication (i.e. steroids, ibuprofen, oral iron) and/or infections (i.e. Helicobacter pylori).

The first part of the small bowel is called the duodenum. It receives digested food particles from the stomach and secretions from both the pancreas and bile ducts to help with digestion.

The jejunum (which connects the duodenum to to the ileum) is responsible for absorption of nutrients.

Crohn’s disease may affect the small bowel which can result in:

Inflammation, causing pain and poor absorption of vitamins and micronutrients

Strictures (narrowing of the bowel) causing pain, bowel obstruction, nausea, and/or vomiting

Fistula formation (abnormal connections between two organs) into other portions of the small bowel or colon (symptoms are not always present)

The ileum is the third part of the small intestine. A function of the ileum is to absorb vitamin B12. Some people with IBD may need supplementation with vitamin B12 after surgery if part of their ileum is removed.

The ileum also absorbs bile acids, which are involved in fat absorption and removal of undigested food.

Patients who have had surgery to remove the ileum may experience diarrhea due to excess bile acids entering the colon.

Imaging tests, including CT, MRI or small bowel series provide a way to evaluate the majority of the small bowel when looking for areas of inflammation, narrowing or fistulas. Read more about diagnosing and monitoring.

The terminal ileum is the end of the small bowel and connects to the beginning of the colon (cecum).

This area can develop strictures (narrowing) due to chronic inflammation and fibrosis (scarring of the intestine).

The terminal ileum is the most common site for inflammation and the most frequently involved area that requires resection (surgical removal) in Crohn’s patients.

Mild redness/irritation in the terminal ileum may occur in patients with pancolitis (inflammation affecting the entire colon) and is known as “backwash ileitis.”

Backwash ileitis is different from the ileal inflammation that can be seen in Crohn’s disease. It does not change a patient’s diagnosis from ulcerative colitis to Crohn’s disease.

This valve separates the colon from the small bowel.

It is a marker of the beginning of the colon and is frequently photographed during a colonoscopy.

Frequently removed during Crohn’s disease surgeries due to narrowing or fistula/abscess formation.

The valve can become “fibrotic” (scarred) and “strictured” (narrowed) with longstanding or aggressive disease.

Occasionally, these narrowings may be treated during colonoscopy with a procedure called a “dilation” which stretches open the narrowing to make it wider.

Some patients with ulcerative colitis have wide, gaping ileocecal valves due to scar tissue.

Located in the cecum (the first part of the colon).

The exact function is not known and surgical removal has no observable health problems.

In left-sided ulcerative colitis or proctitis there may be inflammation surrounding the internal opening of the appendix known as a “cecal red patch.”

The cecum, along with the terminal ileum, are the most frequent parts of the digestive tract that are affected by Crohn’s disease.

There is no association between having your appendix removed (appendectomy) and Crohn's disease.

The cecum is the beginning of the colon and is connected to the small bowel (terminal ileum).

It may or may not be involved in patients with Crohn’s disease due to the patchy nature of Crohn’s disease.

In extensive colitis or pancolitis, the inflammation extends from the rectum to the cecum.

Occasionally, there can be an area of redness in the cecum among patients with left-sided colitis or proctitis called the “cecal red patch.”

This is the first section of the colon located between the cecum and the second part of the colon (transverse/distal colon).

The role of the ascending colon is to absorb the remaining water and other key nutrients from the indigestible material, solidifying it to form stool.

May be affected by Crohn’s disease in the form of inflammation, fistulas (abnormal connections between two organs) or strictures.

Pancolitis or extensive colitis cause continuous inflammation between the rectum through the ascending colon.

Left-sided ulcerative colitis will not involve this area.

The descending colon's main job is to store stool that will ultimately empty into the rectum.

The descending colon is located on the left side of the abdomen.

Rectal inflammation in Crohn’s disease can lead to the development of fistulae (abnormal connections between the rectum, skin or adjacent organs).

Often involved in ulcerative colitis known as “left-sided colitis.”