Colon: Location, Function, and Associated Diseases

Laura Dorwart
·6 min read

Medically reviewed by Robert Burakoff, MD

The colon is a long, tube-like organ that makes up most of the large intestine within the gastrointestinal (GI) tract.

The colon is connected to the small intestine at one end and the rectum at the other, making it a key part of the digestive process. It is responsible for absorbing water and nutrients from undigested food and forming it into solid stool (poop) before defecation.

Several conditions can affect the health of your colon, such as irritable bowel syndrome (IBS) and colon cancer. It's important to get regular testing for colon cancer and take steps to keep your colon healthy.

Anatomy of the Colon

Along with the anal canal and rectum, the colon is part of the large intestine, which is part of the digestive system. Here’s what to know about the anatomy of the colon:

  • Structure: The colon is a muscular, tubular organ and is typically around five feet long. Wider than the small intestine, the colon consists of four segments: the ascending colon (on the right side of the abdomen), the transverse colon (which travels from the right to left side), the descending colon (which carries food and waste downward on the left side), and the sigmoid colon at the bottom.

  • Location: The uppermost part of the colon is the cecum, a pouch just below the ileum (the last part of the small intestine). The cecum is located on the lower right side of the abdomen. The colon then curves over to the left side of the abdomen before the sigmoid colon empties into the rectum, followed by the anus.

  • Anatomical variations: A redundant colon, also called a tortuous colon, has multiple loops, twists, or bends because it is abnormally long and distended. It can lead to abdominal pain and excessive gas as well as constipation and potentially bowel obstruction.

What Does the Colon Do?

When you eat, food travels down your esophagus (the tube connecting your throat to your stomach) and into your stomach, where it’s made into a liquid. Then, the undigested food is broken down by digestive enzymes in the small intestine.

That’s where the colon comes in. The partially digested food passes from the lowest part of the small intestine into the cecum at the top of the large intestine (colon). The colon soaks up water from the food, which forms it into a stool. After the stool moves into the rectum and the anus, it is expelled as a bowel movement.

Along with aiding the digestive process, the colon also helps your body retain its electrolyte balance. The colon absorbs fluids and electrolytes—minerals with an electric charge—from digested food, and slowly releases it into the rest of the body.

Associated Conditions

There are several different conditions that affect colonic health and function, including:

  • Diverticulitis: Diverticulitis involves inflammation or infection in the diverticula—small, bulging pouches in the colonic lining. Symptoms include left-sided stomach pain, fever, chills, vomiting, rectal bleeding, and severe constipation. It’s usually treated with antibiotics.

  • Colon polyps: Polyps—small areas of abnormal tissue growth—sometimes develop in the lining of the colon. Most colonic polyps are benign, but some may lead to colon cancer. Signs of colonic polyps include bloody stool, rectal bleeding, diarrhea, and constipation.

  • Irritable bowel syndrome: Irritable bowel syndrome (IBS) is a gastrointestinal disorder that leads to symptoms like diarrhea, constipation, bloating, and cramps. Anyone can develop IBS, but it’s especially common among women under 45.

  • Ulcerative colitis: Ulcerative colitis (UC), a type of inflammatory bowel disease (IBD), causes ulcers to develop inside the colon and rectum. Symptoms—which may include abdominal pain, blood and pus in the stool, diarrhea, anemia, fatigue, weight loss, and loss of appetite—typically appear before the age of 30.

  • Colon cancer: Colon cancer, or colorectal cancer, leads to symptoms like changes in bowel movements, blood in the stool, bloating, fatigue, unexplained weight loss, and abdominal cramping. Risk factors include a history of colonic polyps, being older than 50, smoking, obesity, and certain genetic mutations. Treatment typically involves surgery to remove the malignant tissue.

Diagnostic Testing

The following procedures allow healthcare providers to assess your colon’s health and function:

  • Colonoscopy: During a colonoscopy, a healthcare provider inserts a long, slender tube attached to a small camera into your anal opening and guides it up to your rectum and colon to look for polyps and other abnormalities. This procedure typically takes about 30-60 minutes. It may be done while you’re sedated or under anesthesia.

  • Flexible sigmoidoscopy: A flexible sigmoidoscopy also involves using a long scope to inspect your sigmoid colon (the lower segment of the colon) and the rectum. However, it usually takes only about 20 minutes and doesn’t require anesthesia.

The recommendation for most people is to start having regular colonoscopies at age 45 to screen for colon cancer and polyps. If you are at a higher risk for colon cancer, your healthcare provider may suggest you start testing earlier.

Tips for Keeping Your Colon Healthy

There are a few ways to lower your risk of colon cancer and other colonic diseases. Lifestyle and diet changes that can help keep your colon healthy include:

  • Staying hydrated: Drinking plenty of water helps to speed up the digestive process and reduce the risk of chronic constipation. This allows your colon to flush out toxins and function more efficiently.

  • Eating plenty of fiber: Eating a high-fiber diet helps manage the symptoms of several colonic diseases, including IBS and diverticulitis. Increase your fiber intake by eating plenty of fruits, vegetables, whole grains, legumes, nuts, and seeds.

  • Reducing your red meat intake: Research shows eating large amounts of red and processed meats can increase your risk of various cancers, including both colon and rectal cancer. Switching to other meats or a more plant-based diet may reduce your risk.

  • Exercising regularly: Physical activity helps regulate the digestive system, allowing food and waste to move more smoothly through the gastrointestinal tract. One study found exercising regularly could prevent 15% of colon cancer cases.

  • Quitting smoking: Studies have shown smoking is associated with a higher risk of both colonic polyps and colorectal cancer. Quit smoking as early as possible, and reach out to your healthcare provider for support and resources if necessary.

A Quick Review

The colon is a long, tube-like organ that makes up most of the large intestine. After food moves through the stomach and small intestine, the colon works to remove fluid from the partially digested food and turn it into solid feces. Keeping your colon healthy is key in maintaining proper function of the digestive system.

Common colonic diseases include colon cancer, irritable bowel syndrome, diverticulitis, colonic polyps, and ulcerative colitis. Staying hydrated, eating a high-fiber diet, and quitting smoking can help to prevent and manage these conditions.

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