Docs Tag: intestine

Crohn’s and Colitis


Inflammatory bowel disease (IBD) describes a group of conditions, the two main forms of which are Crohn’s disease and ulcerative colitis. IBD also includes indeterminate colitis.

Crohn’s disease and ulcerative colitis are diseases that inflame the lining of the GI (gastrointestinal) tract and disrupt your body’s ability to digest food, absorb nutrition, and eliminate waste in a healthy manner.

Below you fill find more information about the anatomy and function of the gastrointestinal (GI) tract, Crohn’s disease and ulcerative colitis.

Dr. Mike Evans is founder of the Health Design Lab at the Li Ka Shing Knowledge Institute, an Associate Professor of Family Medicine and Public Health at the University of Toronto, and a staff physician at St. Michael’s Hospital. This video was made possible through the Gastrointestinal Society, with the support of Crohn’s and Colitis Canada.


In order to understand Crohn’s disease and ulcerative colitis, it is first helpful to understand the anatomy and function of the healthy gastrointestinal (GI) tract. Below is a medical illustration of the GI tract. When you eat, food travels through the GI tract in the following order:


Mouth [ 1 ]

Esophagus [ 2 ] (tube that connects the mouth to the stomach)

Stomach [ 3 ] (food is mixed with stomach acid and enzymes to break down the material into smaller pieces called chyme)

Small Bowel [ 4 ] (or the ‘Small Intestine’) is made up of three sections: Duodenum [ 7 ] (about 8 cm in length); Jejunum [ 8 ] (around 3 metres long); and Ileum [ 9 ] (about 3 metres in length).

The functions of the small bowel are to digest your food and absorb the nutrients. In particular, the jejunum and ileum are the organs responsible for absorbing nutrients from your food. Without the small bowel, we would not be able to convert food into useable nutrition.

Ileocecal Valve [ 5 ] (regulates the amount of material passed from the small bowel to the large bowel and prevents “dumping” all at once)

Large Bowel [ 6 ] (also called the Large Intestine or the Colon). The colon is much wider in diameter than the small bowel and is approximately 1.5 metres long. The different sections of the colon are identified as the:

  • Cecum [ 10 ] and appendix [ 11 ] 
  • Ascending colon
  • Hepatic flexure (a bend in the gut at close to the location of the liver)
  • Transverse colon
  • Splenic flexure (another bend located near the spleen)
  • Descending colon
  • Sigmoid colon
  • Rectum [ 12 ]
  • Anus [ 13 ]

The main functions of the colon are to extract water and salt from stool, and store it until it can be expelled via the anus.

Stool is the by-product of digestion through the GI tract. When stool first enters the colon from the small bowel, it is very watery. As it traverses the large bowel, water is reabsorbed and the stool gradually becomes firmer.
In a healthy individual, it is usually composed of water, dead and living bacteria, fiber (undigested food), intestinal mucous, and sloughed-off lining of the gut. It is not normal to have blood in feces, nor large amounts of mucous. Stool from an individual without any gut disease is soft enough to pass comfortably from the rectum and anus, and (depending on the person) is typically expelled one or two times a day.

Bowel movements are an entirely different matter for someone with Crohn’s or colitis. Individuals with these diseases face some very real challenges related to feelings of urgency, diarrhea, and bloody stool.



Crohn’s disease is named after the doctor who first described it in 1932 (also known as ‘Crohn disease’).

Inflammation from Crohn’s can strike anywhere in the gastrointestinal (GI) tract, from mouth to anus, but is usually located in the lower part of the small bowel and the upper colon.

Patches of inflammation are interspersed between healthy portions of the gut, and can penetrate the intestinal layers from inner to outer lining.

Crohn’s can also affect the mesentery, which is the network of tissue that holds the small bowel to the abdomen and contains the main intestinal blood vessels and lymph glands.




Ulcerative colitis is more localized in nature than Crohn’s disease. Typically, the disease affects the colon (large intestine) including the rectum and anus, and only invades (inflames) the inner lining of bowel tissue.

It almost always starts at the rectum, extending upwards in a continuous manner through the colon. Colitis can be controlled with medication and in severe cases can even be treated through the surgical removal of the entire large intestine.


Indeterminate colitis is a term used when it is unclear if the inflammation is due to Crohn’s disease or ulcerative colitis.


Crohn’s disease and ulcerative colitis are (lifelong) diseases. People with these diseases experience acute periods of active symptoms (active disease or flare), and other times when their symptoms are absent (remission).

Symptoms can include abdominal pain and cramping; severe diarreha; rectal bleeding; blood in stool; weight loss and diminished appetite.

Visit our Signs and Symptoms page for more information. 


There are similarities and differences between Crohn’s disease and ulcerative colitis. We’ve already described above how Crohn’s disease and ulcerative colitis involve different areas of the gastrointestinal tract.

Other characteristics of Crohn’s disease and ulcerative colitis that may differ include: symptoms; the effect of surgery; treatment options; complications or extra-intestinal manifestations; and impact of smoking.

These characteristics are summarized in the table below:

Crohn’s Disease Ulcerative Colitis
Occurrence More females than males
All ages, peak onset 15-35 years
Similar for females and males
All ages, usual onset 15-45 years
Symptoms Diarrhea, fever, sores in the mouth and around the anus, abdominal pain and cramps, anemia, fatigue, loss of appetite, weight loss Bloody diarrhea, mild fever, abdominal pain and cramps, anemia, fatigue, loss of appetite, weight loss
Terminal ileum involvement Common Never
Colon involvement Common Always
Rectum involvement Common Always
Peri-anal disease Common Never
Distribution of disease Patchy areas of inflammation Continuous areas of inflammation but can be patchy once treated
Endoscopic findings Deep and snake-like ulcers Diffuse ulceration
Depth of inflammation May be transmural, extending through the entire thickness of the wall of an organ or cavity deep into tissues Shallow, mucosal
Fistulas between organs Common Never
Stenosis Common Never
Granulomas on biopsy Common Never
Effect of surgery Often return following removal of affected parts. Decreased likelihood of pregnancy. Usually cured by removal of colon (colectomy). Decreased likelihood of pregnancy after ileoanal pouch.
Treatment options Drug treatment (corticosteroids, immune modifiers, biologic therapies). Exclusive formula diet in children. Surgery (repair fistulas, remove obstruction, resection, and anastomosis). Drug treatment (5-aminosalicylates, sulfasalazine, corticosteroids, immune modifiers, biologic therapies). Surgery (rectum/colon removal) with creation of an internal pouch (ileoanal pouch).
Cure No existing cures. Maintenance therapy is used to reduce the chance of relapse. Through colectomy only. Maintenance therapy is used to reduce the chance of relapse.
Bowel complications Blockage of intestine due to swelling or formation of scar tissue. Abscesses, sores, or fistulas. Malnutrition. Colon cancer. Bleeding from ulcerations. Perforation (rupture) of the bowel. Malnutrition. Colon cancer.
Extra-intestinal disease Osteoporosis. Liver inflammation (primary sclerosing cholangitis). Blood clots. Pain and swelling in the joints (arthritis). Growth failure (in children). Mental Illness. Liver inflammation (primary sclerosing cholangitis). Blood clots. Eye inflammation (iritis). Pain and swelling in the joints (arthritis). Mental illness.
Smoking Higher risk of acquiring for smokers Higher risk of acquiring for ex-smokers
Mortality risk Increased risk of colorectal cancer and overall mortality. Increased risk of lymphoma and skin cancer (due to treatments). Increased risk of colorectal cancer. Uncertain change in mortality risk. Increased risk of lymphoma and skin cancer (due to treatments).

Image reference. Impact of Inflammatory Bowel Disease in Canada. 2018.

Information taken from https://crohnsandcolitis.ca/About-Crohn-s-Colitis/What-are-Crohns-and-Colitis




Celiac Disease


Celiac disease (CD) is a common disorder that is estimated to affect about one percent of the population. It is a condition in which the absorptive surface of the small intestine is damaged by a substance called gluten. Gluten is a group of proteins present in wheat, rye and barley and their cross bred grains. The damage to the intestine can lead to a variety of symptoms and result in an inability of the body to absorb nutrients such as protein, fat, carbohydrates, vitamins and minerals, which are necessary for good health.


Patients with CD can present with a variety of symptoms. The classical (typical) symptoms include chronic diarrhea, abdominal pain, malabsorption and weight loss. However, many patients now present with non-classical (atypical) symptoms including anemia, osteoporosis, extreme fatigue, oral ulcers, liver enzyme abnormalities, constipation, infertility, dental enamel defects, neurological problems, etc. Children can present with short stature, irritability, vomiting, etc.

Celiac disease occurs commonly in patients with other autoimmune disorders such as thyroid disease and type-I diabetes. It can also run in families, both in first and second degree relatives. Therefore, screening of these high risk individuals should be considered.

Since many patients with CD do not present with classical symptoms, delays in diagnosis can occur.

Dermatitis herpetiformis is “celiac disease” of the skin. The patients present with severely itchy blistering rash. The diagnosis can be confirmed with a skin biopsy. Treatment consists of strict gluten-free diet and, in some cases, medications.

Information taken from; https://www.celiac.ca/gluten-related-disorders/celiac-disease/


Inflammatory Bowel Disease

What Do Teens Need to Know About IBD?
Let’s talk basics. Inflammatory bowel disease (IBD) is a chronic, lifelong disease that causes inflammation of the gastrointestinal (GI) tract. The two main types of IBD are Crohn’s disease and ulcerative colitis.

Your GI tract is responsible for digestion of food, absorption of nutrients, and elimination of waste from your body. The GI tract starts with your mouth and continues down your throat into your esophagus, and through your stomach, small intestine, large intestine, and rectum, ending with your anus. Inflammation caused by IBD makes the affected GI organs work improperly.
Information taken from https://www.crohnscolitisfoundation.org/youth-parent-resources/teens



What is a Colonsocopy?

Colonoscopy is a test that takes pictures of your large intestine. The test is called a colonoscopy because colon means your large intestine and scopy means a scope (a tiny camera that looks around and takes pictures). The colon is very large and it has names for its different parts.

Why do I need to have a Colonoscopy?

The doctor needs to see inside your large intestine (colon) to see how it is working and to find out what they need to do to help you. An X-Ray cannot see inside the large intestine, so a colonoscopy has to be done.

What does a Colonoscopy look like?

A colonoscopy has a tiny video camera (scope) and a light at the end of a small very flexible (bendy) tube; there is also a computer and TV screen that is used.  The light helps the doctor see in your colon. The video camera can take a video or pictures of inside your large intestine (colon). This will help the doctor to see what is happening inside your body. There is also a bed that is beside the computer where you will lie down.

What happens when I have a Colonoscopy?

A porter will come to bring you to the special room to have the colonoscopy.  A nurse and gastroenterologist (a doctor who is the expert about intestines) will greet you and explain what will happen.

The nurse will give you a gown to wear, this looks like a backward housecoat, you may already be wearing one. The nurse will help you to get on the bed; she will also tell you to lie on your left side. This is the best way for you to lie down for the test. The nurse will put a blanket over you to keep you warm and make sure you are covered up. The nurse will also put a plastic clip onto your finger. This clip does not hurt and it glows red. This clip is called an Oximeter and it measures how much oxygen you have in your blood. You will also have a blood pressure cuff put on your arm to measure how fast or slow your blood is moving around your body. The blood pressure cuff will go on and give your arm a little squeeze and then off, relaxing it. This happens a few times during the test.

The doctor will put on hospital gloves. Then he will take the scope and he will place it gently into the opening in your bum (this is also called an anus). The scope goes into your bum because that is where the large intestine is; it ends at your bum.

While the doctor is looking in your large intestine, he will also be taking pictures of it. He may also take a tiny piece of the large intestine to look at it more closely, this is called a biopsy. It is important to remember to relax and lie still. Once the test is done, the scope will be removed.

Someone like your mom or dad can stay in the room with you during the test. The test can take about 45 minutes to complete. When it is over, you will rest for a little while and then you will be brought back to your room.

Click here to check out a colonoscopy booklet created by Windsor Regional Hospital


What will the Colonoscopy feel like?

The colonoscopy will feel uncomfortable when the scope first goes into your bum. You may feel pressure in your bum; you may feel that you have to go to the bathroom. Your stomach may also feel a little sore, like a stomach ache. All of these feelings are normal, this happens to everyone who has this test.

Preparing for the test

Your nurse will give you the information you need to help you get ready to have your colonoscopy. You will be told that you will not be able to eat or drink anything before the test. Your nurse will give you a special medicine that you will need to drink. This special drink will help to clean out your intestine. Your intestine is where your body stores the stuff that your body does not need anymore, this is called stool (or poop). Before you have the test, all your stool needs to be out of your intestine. This special drink helps you to go to the bathroom a lot so that all the stool gets out.

You may also be given a special medicine before the test that makes you feel sleepy and help you relax. This medicine goes into your IV. If you do not already have an IV, the nurse will give you one. The IV is a small straw that goes into the vein usually in your hand. This is the quickest way to get the sleepy medicine into your body. You will feel a pinch from the poke of the IV, and it may hurt a little.  Remember the needle used to get the straw into your hand, comes out and is put into a special garbage. All that is in your hand is a tiny bendy straw, no needle (to learn more about IV?s, go to the ?What is that? section). When it is time for the test, remember to relax and take deep breaths.


If you have any questions about the test, always ask!

This content has been reviewed and approved by health care team members at McMaster Children’s Hospital in Hamilton, Ontario. All content is for educational purposes only. For further information, please speak with your health care team.