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What is the rectum?
Your rectum is at the end of your large intestine, a long, continuous tube that includes your colon, rectum and anus. Your rectum makes up the last 6 inches or so, just before it turns into the anal canal. This is the last stop on your food’s journey through your gastrointestinal (GI) tract before it exits. As food waste passes from your colon into your rectum, it collects there until nerves trigger the urge to poop.
What is the difference between the colon and rectum?
Your rectum continues from your colon and is made of the same stuff: layers of muscles and tissues, with glands on the inside that secrete and absorb. Your colon is much longer, and food traveling through your colon is still in the process of digestion. By the time it reaches your rectum, it’s been reduced to solid waste. Your rectum holds the waste and absorbs the remaining water until it’s time to release it.
What is the difference between the rectum and the anus?
Your anal canal continues from your rectum and makes up the last few centimeters of your large intestine. The anus contains important muscles (anal sphincters) that control your bowel movements.
How does the rectum function in your digestive system?
The primary function of the rectum is to collect and hold your poop until it’s time to release it. Your rectum relaxes and stretches to accommodate the waste as it gradually comes in from your colon. While holding it, your rectum absorbs the remaining water and electrolytes and further solidifies the waste. It secretes mucus to help it pass through smoothly. When it’s full, nerves trigger the urge to poop.
Where is the rectum?
Your large intestine surrounds your small intestine, lying loosely around the edges of your abdominal cavity. Your rectum, at the end of it, curls under your abdominal organs, toward your anus. It exists in the pelvic cavity between your abdomen and pelvis floor muscles. The top connects to your sigmoid colon and the bottom connects to your anus.
How long is the rectum?
It averages between 10 and 15 centimeters, which is about 5 or 6 inches long. When its muscles activate to move waste through, it can contract and shorten, like a slinky. Like the rest of the large intestine, it’s about 3 inches wide, which makes it about half as wide as it is long. But it also stretches wider than the rest of the intestine to accommodate more waste, acting as a reservoir.
What are the parts of the rectum?
The rectum has a slight “S” shape, with two bends in it. The one near the top (sacral flexure) follows the curve of your spine, while the one near the bottom (anorectal flexure) marks the transition from rectum to anus. These bends help control continence (holding your poop in). The rectum also has segments, like a worm, which are separated by horizontal folds in the inner lining called the valves of Houston.
The three or four chambers of the rectum help to control the movement of contents through it. The last chamber, called the rectal ampulla, is the final reservoir for poop before it comes out. When this chamber fills, nerve fibers that detect stretch in the rectal wall (stretch receptors) communicate to your central nervous system that it’s time to defecate. Increasing pressure will make it increasingly hard to hold it in.
Conditions and Disorders
What are the common conditions and disorders that affect the rectum?
Rectal disorders can affect the inside lining, muscles or nerves of the rectum, causing pain and interfering with its function. Common conditions include:
- Proctitis. Proctitis is inflammation in your rectum. Infections (especially STIs) may cause temporary (acute) proctitis. Inflammatory bowel disease may cause chronic proctitis.
- Rectal ulcers. Ulcers are painful open sores, which may bleed.
- Perianal abscess. A painful, pus-filled lump may occur near your rectum, anus or perineum.
- Colorectal polyps. Polyps, or growths, in your rectum are common and not always cause for concern, but some may develop into colorectal cancer.
- Rectal prolapse. Wear and tear on the muscles that hold your rectum in place can cause it to fall out of place, telescoping into your anal canal.
- Levator syndrome. Levator syndrome is named for the levator ani muscle that holds your rectum in place. It causes episodic rectal pain, which is usually attributed to muscle spasms.
- Fecal incontinence. Problems with the muscles or nerves in your rectum can cause difficulty holding your poop in leading to accidents or leakage.
- Obstructed defecation. Physical and psychological issues can cause difficulty pooping. This can be from a loss of sensation or muscle coordination in your rectum (pelvic floor dysfunction).
- Constipation and fecal impaction. Difficulty pooping and not pooping enough can lead to hard, impacted poop plugging your rectum.
What are the common signs and symptoms of possible rectal disorders?
You might want to see a healthcare provider about your rectal health if you notice:
- Rectal bleeding in your underwear or in the toilet.
- Anorectal pain or pain that feels like it’s in your lower abdomen or pelvis.
- Anal itching or signs of infection in your anus.
- Poop changes, such as changes to the color, consistency or frequency of your poop.
- Feeling like you constantly have to poop (tenesmus) or like pooping is difficult and painful (dyschezia).
- A fleshy bulge protruding through your anus (pelvic organ prolapse).
How do healthcare providers check on the health of my rectum?
Medical tests to examine the rectum include:
- Digital rectal exam. This is a physical exam using a gloved and lubricated finger inserted into your rectum. A DRE may be part of a routine physical exam or gynecological exam to examine not only your rectum but also your prostate or cervix, through the wall of your rectum.
- Rectal culture. For this test, a healthcare provider swipes the inside of your rectum with a cotton swab and then places it in a culture to identify bacteria or viruses in the sample.
- Stool test. A healthcare provider may test a sample of your poop (stool) for evidence of infection, bleeding or an excess of white blood cells.
- Anorectal manometry. This test measures how well your muscles and nerves work together to push poop out. A catheter with a balloon attached is inserted into your rectum and the balloon is inflated with warm water. The other end of the catheter is attached to a machine that’ll measure your muscle activity.
- Defecography. This test takes X-ray or MRI imaging of your insides while you try to poop, to examine how the different organs and muscles are working. A healthcare technician will inject a medical substance into your rectum for you to push out like you would a stool. You’ll do so in a private photographic chamber while they watch your organs on a computer screen outside.
- Barium enema. This is a type of GI X-ray exam that takes fluoroscopic (video X-ray) imaging of your large intestine, including your rectum. The barium enema is a contrast dye that’s injected into your rectum, like an enema, to help it show up better in the black-and-white images.
- Proctoscopy. A proctoscopy is an examination of the inside of your rectum with a short, rigid scope. The proctoscope is a hollow tube with a lighted camera at the end. If needed, a healthcare provider can pass an instrument through the tube to take a tissue sample for biopsy.
- Flexible sigmoidoscopy. Your provider might use a slightly longer scope, called a flexible sigmoidoscope, if they want to see a little further in to examine the end part of your colon, where it meets your rectum (your sigmoid colon). If your colon is involved, it might indicate inflammatory bowel disease (IBD) or a gastrointestinal infection. This test will require a bowel prep.
How can I keep my rectum healthy?
Not all rectal conditions are preventable, but you can reduce your risk of certain conditions by following these basic health guidelines:
- Practice safe sex. Sexually transmitted infections (STIs) that infect your anus can also infect your rectum. Screen your partners for STIs and when in doubt, use protection.
- A healthy diet makes for healthy poops. More whole foods and fewer processed foods will help prevent constipation and straining, which can lead to many other problems.
- Get your colonoscopy. A routine colonoscopy is an important way of screening for rectal polyps and preventing rectal cancer.
- Don’t ignore symptoms. If you have persistent pain, poop changes or pooping difficulties, see a healthcare provider before it gets worse.
A note from Cleveland Clinic
Your rectum is an important bridge between your digestive process and the defecation process. Your colon at one end and your anus at the other end may affect, or be affected by, your rectal health. Difficulties with your rectum can cause significant discomfort as well as embarrassment, but it’s important to get the help you need. A gastroenterologist or proctologist can help diagnose and treat rectal conditions.
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