One of the primary differences between anal and rectal cancer is what causes them. Anal cancers are strongly associated with HPV and HIV infections, while rectal cancers are often linked to genetic mutations (inherited or acquired) and lifestyle factors.
Anal cancer and rectal cancer both develop in the lowest sections of your digestive tract. The rectum holds stool until you’re ready to have a bowel movement, and the anus pushes it out.
You might think cancers in these two areas are the same, but they’re really set apart by what causes them. This article will explore the causes, symptoms, and treatments you might expect if you receive a diagnosis of either rectal or anal cancer.
Anatomical location and cause are the primary differences between anal cancer and rectal cancer.
Location
Rectal cancers occur in the rectum, which is the last section of the large intestine between the colon and the anus. Anal cancers occur in the anus, the canal through which stools pass just before leaving your body.
Bowel anatomy explained
There are some differences in the causes and symptoms of the different bowel cancers, but understanding the anatomy of each is key.
- The colon: It’s about
5 feet long , and can be divided into four sections: the ascending, transverse, descending, and sigmoid colon. These sections are the final processing points for your body’s nutrients and waste. It’s where water, electrolytes, and other nutrients are absorbed back into the body, and stools are formed from the remaining solid waste products. - The rectum: This is a section at the base of the large intestine that joins the colon and the anus. The rectum is about 10 to 15 centimeters long and stores stools until you’re ready to have a bowel movement.
- The anus: This is the final
4 to 5 centimeter section of the digestive tract that pushes stool from the rectum out of your body during a bowel movement.
Causes
Anal cancers are primarily associated with human papilloma virus (HPV) infections and HIV cases, as well as chronic conditions or treatments that weaken the immune system.
In the United States, an estimated
Lifestyle factors, such as cigarette smoking, alcohol consumption, lack of exercise, and a diet high in fat and low in fiber, also play a role in the development of colorectal cancer.
There’s some overlap between symptoms of anal cancer and
| Symptoms | Anal cancer | Rectal cancer |
| Rectal bleeding | X | X |
| Blood or mucous in your stools | X | X |
| A discharge of mucus or pus from your anus | X | |
| Abdominal pain or cramping | X | |
| Diarrhea or loose stool | X | |
| Loss of bowel control (fecal incontinence) | X | |
| Itching and pain around the anus | X | |
| Small lumps around the anus | X | |
| A feeling that you need to go poop but the feeling isn’t relieved when you go poop | X | |
| A change in bowel habits, such as diarrhea, constipation, or narrowing of the stools | X | |
| Fatigue or weakness | X | |
| Unintentional weight loss | X |
Rectal cancer can be caused by several things, although experts haven’t pinpointed a singular cause. Researchers believe genetic mutations acquired during your lifetime or inherited from your parents can cause rectal cancer, as well as certain
Anal cancer, on the other hand, is often caused by infection with HIV or one of the many types of HPV, which is the virus family also responsible for conditions like genital warts and cervical cancer. Having a weakened or suppressed immune system can also increase your risk for anal cancer.
Both rectal and anal cancer can be treated with chemotherapy, radiation, or a combination of these two therapies. In some cases, surgical removal of a tumor or cancerous area is also possible.
However, depending on what needs to be removed and if the anal sphincter is affected, you may need to permanently reroute your stool with a colostomy. The anal sphincter is the muscular area that helps you maintain control of your bowels, so a loss of function could result in fecal incontinence.
Preventing anal and colorectal cancers
A vaccine is now available to help protect you against HPV infections that cause cancers and other health conditions. You can also lower your risk of anal cancer by quitting smoking, if you smoke, and using condoms or other barrier protection methods with sexual partners.
Rectal cancers are a bit more difficult to prevent, since many cases of these cancers are the results of inherited genetic mutations. However, making the following diet and lifestyle choices can help you avoid developing noninherited forms of rectal cancer.
- Maintain a moderate weight and balanced diet.
- Stay active and exercise regularly.
- Avoid high fat foods and processed meats.
- Make sure you get enough fiber in your diet, eating plenty of fruits and vegetables.
- Limit your alcohol consumption.
- Quit smoking, if you smoke.
The 5-year relative survival rates for anal and rectal cancers are similar. Rectal cancers are usually grouped into a category with colon cancers, collectively called colorectal cancer.
The overall
The above rates are based on people in the United States diagnosed with anal and colorectal cancers between 2011 and 2017. Survival rates vary by the stage of your cancer when it was diagnosed, and whether it has spread to other areas of the body.
What is a 5-year relative survival rate?
A relative survival rate gives you an idea of how long someone with a specific condition may live after their diagnosis compared with someone without the condition. For example, a 5-year relative survival rate of 69% means that someone with that condition is 69% as likely to live for 5 years as someone without the condition.
It is important to remember that these figures are estimates. Talk with your doctor about your specific situation.
Anal and rectal cancer can both cause similar symptoms, like blood in your stool, but not every symptom is the same, and the causes are quite different.
Talk with a doctor if you notice a change in your bathroom habits or bowel movements.
There are a number of tests and examinations that will help a doctor make an exact diagnosis and guide the best treatment options for your specific type and stage of cancer.