Large Intestine & Colon

What is the large intestine?

Your large intestine is part of your digestive system. It turns food waste into solid poop (stool) and drives the pooping process. Issues with your large intestine can lead to everyday conditions like constipation or diarrhea. They can also lead to more serious conditions like colorectal cancer. Eating well, not smoking and having screening tests for cancer can keep your large intestine healthy.

What does the large intestine do?

Your large intestine receives the liquid food waste that’s left after your small intestine completes its part of the digestive process. It absorbs water and salts from the liquid waste and turns it into solid waste (poop). Your large intestine uses layers of tissue and muscles to move poop out of your body.

Where is the large intestine located?

Your large intestine loops around your belly and your small intestine. It moves from a spot near your right hip up to your ribs. Then, it moves across your body and back down the left side of your belly. It’s 6 feet (1.8 meters) long and about 3 inches (about 8 centimeters) in diameter.

What are the parts of the large intestine?

Your large intestine has three parts: the colon, rectum and anus. Each part does specific things to keep food waste moving through your large intestine.

The colon

Your colon has five parts that work to process food waste and move waste to your rectum. Those parts are:

• Cecum: This is the first part of your colon. It’s about 3 inches (8 cm) long. Your cecum receives digested food waste from your small intestine and moves it along to your ascending colon. Your appendix hangs off the end of your cecum.
• Ascending colon: This is the second part of your colon. It’s about 8 inches (20 cm) long and 2.5 inches (6 cm) around. It runs from your cecum up to your transverse colon. It absorbs water and electrolytes in food waste. It then moves the waste up and sideways to your transverse colon.
• Transverse colon: This is the longest part of your colon, measuring more than 18 inches (46 cm). It runs from right to left at the top of your abdomen. It carries food waste to your descending colon.
• Descending colon: Your descending colon is about 6 inches (15 cm) long. It sits on the left side of your body. It continues the process of turning food waste into poop.
• Sigmoid colon: Your sigmoid colon, which is about 14 to 16 inches (35 to 40 cm) long, is the last part of your colon. It represents the final step in turning food waste into a solid mass that resembles the poop that you typically see in your toilet bowl.

The rectum

Your rectum is about 5 to 6 inches (12 to 15 cm) long. By this time in the digestive process, the parts of your large intestine reduce liquid waste by about one-third of its original size. For example, if about 16 ounces (474 milliliters) of liquid food enter your large intestine, about 5 ounces (148 ml) of that food remains as poop. When poop enters your rectum, it triggers your body’s urge to poop.

The anus

This is the canal your poop goes through to leave your body. It’s about 2 inches (5 cm) long. Your anus has muscle sphincters that manage how poop leaves your body.

A sphincter is like a fist that opens and closes. Your internal sphincter opens automatically to let poop through. The outer sphincter is the one you control to let poop out when you’re ready to go.

When poop in your rectum triggers the urge to defecate, nerve signals cause your internal sphincter to relax. This is your cue to find a toilet where you can let the poop out through your external sphincter.

What does the intestine look like?

It looks like a deflated tube with segments (think of the ridges in a vacuum cleaner hose). There’s a vertical seam that runs down the middle of your large intestine. The seam makes the segments bulge on the other side of it.

What are the common conditions and disorders that affect the large intestine?

A wide range of conditions and diseases can affect your large intestine, including ones specific to your colon, rectum and anus. Common issues include:

• Anal fistula and anal fissures.
• Constipation.
• Colorectal cancer and colon polyps.
• Diarrhea.
• Fecal incontinence.
• Hemorrhoids.
• Inflammatory bowel disease.
• Intestinal pseudo-obstruction.
• Irritable bowel syndrome (IBS).
• Large bowel obstruction.
• Pelvic floor dysfunction.
• Rectal bleeding and rectal prolapse.

What symptoms might indicate a problem with the large intestine?

Many things may signal issues in your large intestine, but some common symptoms are:

• Changes in your bowel habits, like diarrhea or constipation, trouble pooping or holding poop in.
• Changes in your poop, like bleeding, color or consistency changes.
• Painful bloating and gas could be symptoms of a food intolerance.
• Significant fatigue. This symptom could be from a lot of things, but gut issues are on the list.

What medical tests can check on the health of the large intestine?

A healthcare provider may recommend you have colonoscopies to screen for colon cancer. If you have symptoms, a provider may order one or more of the following tests:

• Anorectal manometry.
• Barium enema.
• Endoscopic ultrasound.
• Flexible sigmoidoscopy.
• Lower GI X-ray exam.
• Proctoscopy.
• Stool test.

What medical procedures are treatments for large intestine conditions?

Treatments vary depending on the condition that affects your large intestine. Some common procedures are:

• Colectomy.
• Colostomy.
• Laparoscopic abdominoperineal resection.
• Laparoscopic rectopexy.
• Rectocele repair.
• Transanal endoscopic microsurgery.

How can I keep my large intestine healthy?

These general health guidelines will help you maintain a healthy gut:

• Eat more fiber: Fiber triggers the muscle contractions that move food through your colon and helps clear out residue there that could slow things down. Eating leafy greens and fruit is the best way to boost your fiber intake.
• Eat better fats: Saturated fats, such as those found in red meat, are associated with higher rates of colon diseases. On the other hand, healthy fats — the omega-3s found especially in oily fish — promote friendly bacteria in the gut.
• Drink more water: Your gut uses a lot of water — for cleansing, lubricating and absorbing nutrients — and most of us don’t drink enough of it.
• Get your colonoscopy: Colon cancer is both common and preventable. Anyone with a colon can get it, and by the time you have symptoms, it might be too late to treat it. Regular screening is the best way to prevent it and treat it in time.