What Is the Colon?

The colon, or large intestine, plays a large role in our gastrointestinal system. What is it exactly? And why is it so important? House Call Doctor explains.

Sanaz Majd, MD
Episode #110

What Is the Colon?

by Sanaz Majd, MD

The colon plays a large role in our gastrointestinal system. It’s also commonly referred to as the “large intestine.” But what is it exactly? And why is it so important? That’s what we’ll be discussing today.

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What Is the Colon?

The colon is the large “end” of our digestive tract, running approximately 5 feet in length. When we consume food, it first enters the mouth, makes its way down the long tubular esophagus, and into the stomach which sits below our sternum. From the stomach, it then enters the small intestines where most of our nutrients are absorbed, and then finally to the colon. 

The colon consists of four parts, which are all in an arch within the abdomen – the ascending running up the right side, transverse running across the top, descending goes down the left side, and the sigmoid colon ends in the rectum/anus where our bowels exit. 

The colon has several functions in the body, with the two main ones being water and salt absorption. In addition, the bacteria that normally reside here further break down any left-over carbohydrates that the small intestines left undigested. The digestion of these carbs produces carbon dioxide, hydrogen, and sometimes methane, which then exits the colon in one of the most popular topics of party conversation and second-grade humor – flatulence. 

Diseases of the Colon

Like any other part of the body, things can go wrong here. Several disorders arise from abnormal colon health. Here are some of the most likely illnesses of the colon:

1. Colon cancer: This is the third most common cancer in the United States. It happens when the lining of the inside of the colon goes haywire and over produces malignant cells that turn into tumors. 

2. Diverticulitis: The lining of the colon can also result in outpouchings called “diverticula,” which are very common. However, in a small percentage of patients, when small food particles, such as popcorn, nuts, and seeds, get caught within these outpouchings, they can inflame the lining and cause an infection.

3. Colon polyps: The lining of the colon can also form little bulbs of tissue, called “polyps.” And although many are considered benign, some can have the potential to turn into colon cancer and are, therefore, removed.

4. Colitis: When the lining of the colon becomes inflamed, we call this “colitis.” This can occur for several reasons. First, patients can acquire a hereditary condition called Ulcerative Colitis or Crohn’s disease, which is a more rare cause of colitis. Second, antibiotics can predispose someone to bacterial overgrowth of C.Diff bacteria, which commonly causes colitis. And, third, viruses and other bacteria can also inflame the lining of the colon.

What Is a Colonoscopy?

A colonoscopy is an important but routine test that is recommended in order to screen for colon cancer. It consists of a long, tubular, fiber-optic telescope, which is inserted into the rectum and advanced into the colon in search of polyps and abnormalities that can be removed or biopsied. 

A colonoscopy is generally recommended starting at age 50 and performed every 10 years (as long as your first result is normal). However, in those with a first degree relative who has  a history of colon cancer, screening is recommended starting 10 years prior to when that relative was first diagnosed. And no, that doesn’t include your third cousin twice removed. A first degree relative is a parent or a sibling. So, for example: if your parent had colon cancer at age 52, your first colonoscopy should be done at age 42 (eight years earlier than  the rest of the general population).

Do you have a history of colon cancer in your family? Have you had your colonoscopy? Remind your doctor to send you that referral!

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Please note that all content here is strictly for informational purposes only. This content does not substitute any medical advice, and does not replace any medical judgment or reasoning by your own personal health provider. Please always seek a licensed physician in your area regarding all health related questions and issues.

Woman with Stomach Ache image from Shutterstock

About the Author

Sanaz Majd, MD

Dr. Sanaz Majd, a board-certified Family Medicine physician who graduated from Drexel University College of Medicine in Philadelphia. She sees everything from pediatrics to geriatrics, but her special interests are women's health and patient education. She also loves to teach, and has been doing so since her college days.

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