Small bowel cancer is an uncommon type of cancer that occurs in the small intestine. Your small intestine, which is also called the small bowel, is a long tube that carries digested food between your stomach and your large intestine (colon).

The small intestine is responsible for digesting and absorbing nutrients from the foods you eat. It produces hormones that help with digestion. The small intestine also plays a role in your body's germ-fighting immune system, as it contains cells that fight bacteria and viruses that enter your body through your mouth.

Types of small bowel cancer include:

• Adenocarcinoma
• Neuroendocrine tumors, including carcinoid tumors and paraganglioma
• Lymphoma
• Sarcoma, including gastrointestinal stromal tumor (GIST)

What treatment options are best for you depend on the type of small bowel cancer you have and its stage.

Signs and symptoms of small bowel cancer include:

• Abdominal pain
• Yellowing of the skin and the whites of the eyes (jaundice)
• Feeling unusually weak or tired
• Nausea
• Vomiting
• Losing weight without trying
• Blood in the stool, which might appear red or black
• Watery diarrhea
• Skin flushing

Doctors aren't certain what causes most small bowel cancers.

In general, small bowel cancer begins when healthy cells in the small bowel develop changes (mutations) in their DNA. A cell's DNA contains a set of instructions that tell a cell what to do.

Healthy cells grow and divide in an orderly way to keep your body functioning normally. But when a cell's DNA is damaged and becomes cancerous, cells continue to divide — even when new cells aren't needed. As these cells accumulate, they form a tumor.

With time, the cancer cells can grow to invade and destroy normal tissue nearby. And cancerous cells can spread (metastasize) to other parts of the body.

Factors that may increase the risk of small bowel cancer include:

• Gene mutations passed through families. Some gene mutations that are inherited from your parents can increase your risk of small bowel cancer and other cancers. Examples include Lynch syndrome, familial adenomatous polyposis (FAP) and Peutz-Jeghers syndrome.
• Other bowel diseases. Other diseases and conditions that affect the intestines may increase the risk of small bowel cancer, including Crohn's disease, inflammatory bowel disease and celiac disease.
• Weakened immune system. If your body's germ-fighting immune system is weakened, you may have an increased risk of small bowel cancer. Examples include people with HIV infection and those who take anti-rejection medicine after an organ transplant.

Small bowel cancer can cause complications, including:

• An increased risk of other cancers. People who have small bowel cancer run a higher risk of having other types of cancers, including those that affect the colon, rectum, ovaries and the lining of the uterus (endometrium).
• Cancer that spreads to other parts of the body. Advanced small bowel cancer can spread (metastasize) to other parts of the body, most often the liver.

It's not clear what may help to reduce the risk of small bowel cancer, since it's very uncommon. If you're interested in reducing your risk of cancer in general, it may help to:

• Eat a variety of fruits, vegetables and whole grains. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may help reduce your risk of cancer and other diseases. Choose a variety of fruits and vegetables so that you get an array of vitamins and nutrients.
• Drink alcohol in moderation, if at all. If you choose to drink alcohol, limit the amount of alcohol you drink to no more than one drink a day for women of all ages and men older than age 65, and up to two drinks a day for men age 65 and younger.
• Stop smoking. Talk to your doctor about ways to quit that may work for you.
• Exercise most days of the week. Try to get at least 30 minutes of exercise on most days. If you've been inactive, start slowly and build up gradually to 30 minutes. Also, talk to your doctor before starting any exercise program.
• Maintain a healthy weight. If you are at a healthy weight, work to maintain your weight by combining a healthy diet with daily exercise. If you need to lose weight, ask your doctor about healthy ways to achieve your goal. Aim to lose weight slowly by increasing the amount of exercise you get and reducing the number of calories you eat.

Small bowel cancers are difficult to diagnose. For this reason, people suspected of having small bowel cancer often undergo multiple tests and procedures to locate the cancer or rule out a cancer.

Imaging tests

Imaging tests use machines to create pictures of the body in order to look for signs of small bowel cancer. Imaging tests used to diagnose small bowel cancer include:

• CT
• MRI
• Positron emission tomography (PET)
• X-rays of the upper digestive system and small bowel after drinking a solution containing barium (upper gastrointestinal series with small bowel follow-through)
• Nuclear medicine scans, which use a small amount of radioactive tracer to enhance imaging tests

Tests to see inside your small intestine

Endoscopic tests involve placing a camera inside your small intestine so that your doctor can examine the inside walls. Endoscopic tests may include:

• Upper endoscopy
• Capsule endoscopy, which is sometimes called a pill camera
• Single-balloon enteroscopy
• Double-balloon enteroscopy
• Spiral enteroscopy

Endoscopic tests, other than the capsule endoscopy, allow doctors to pass special tools into the small intestine to remove tissue samples for testing.

Surgery

Sometimes small bowel cancers are located in places that make them very difficult to see with other tests. In these cases, your doctor may recommend surgery to examine your small intestine and the surrounding area for signs of cancer.

Surgery can involve one large incision in your abdomen (laparotomy), or it can involve several small incisions (laparoscopy).

During laparoscopy, your surgeon passes special surgical tools through the incisions, as well as a video camera. The camera allows the surgeon to guide the tools and see inside your abdomen.

Treatment for small bowel cancer depends on the type of cancer you have and its stage. Options might include:

• Surgery. Surgeons work to remove all of the small bowel cancer, when possible. If cancer affects a small portion of the small intestine, surgeons may remove only that section and rejoin the cut ends of the intestine. In some cases, all of the small intestine may need to be removed.

  If a small bowel cancer can't be removed, surgeons might perform a bypass to relieve a blockage in the small intestine.

• Chemotherapy. Chemotherapy uses powerful drugs to kill cancer cells. Chemotherapy usually involves a combination of medications that kill fast-growing cells, including cancer cells. It's typically given through a vein in your arm, but can also be in pill form.

  For small bowel cancer, chemotherapy might be recommended after surgery if there's a risk that the cancer could return. For advanced cancer, chemotherapy might help relieve signs and symptoms.

• Targeted drug therapy. Targeted drug treatments focus on specific weaknesses present within cancer cells. By blocking these weaknesses, targeted drug treatments can cause cancer cells to die. Targeted drugs might be used for certain types of small bowel cancer, including gastrointestinal stromal tumor (GIST) and lymphoma.
• Immunotherapy. Immunotherapy is a drug treatment that helps your immune system to fight cancer. Your body's immune system might not attack cancer because the cancer cells produce proteins that blind the immune system cells. Immunotherapy works by interfering with that process. Immunotherapy might be an option for advanced small bowel cancer if testing shows the cancer cells may respond to this type of treatment.

With time, you'll find what helps you cope with the uncertainty and distress of a small bowel cancer diagnosis. Until then, you may find it helps to:

• Learn enough about small bowel cancer to make decisions about your care. Ask your doctor about your cancer, including your test results, treatment options and, if you like, your prognosis. As you learn more about small bowel cancer, you may become more confident in making treatment decisions.
• Keep friends and family close. Keeping your close relationships strong will help you deal with your small bowel cancer. Friends and family can provide the practical support you'll need, such as helping take care of your house if you're in the hospital. And they can serve as emotional support when you feel overwhelmed by cancer.

• Find someone to talk with. Find a good listener who is willing to listen to you talk about your hopes and fears. This may be a friend or family member. The concern and understanding of a counselor, medical social worker, clergy member or cancer support group also may be helpful.

  Ask your doctor about support groups in your area. Other sources of information include the National Cancer Institute and the American Cancer Society.

Make an appointment with your doctor if you have any signs or symptoms that worry you. If your doctor suspects you might have cancer, you may be referred to a specialist.

Here's some information to help you get ready for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do in advance, such as fasting before having a specific test. Make a list of:

• Your symptoms, including any that seem unrelated to the reason for your appointment
• Key personal information, including major stresses, recent life changes and family medical history
• All medications, vitamins or other supplements you take, including the doses
• Questions to ask your doctor

Consider bringing a family member or friend to help you remember the information you're given.

For small bowel cancer, some basic questions to ask your doctor include:

• What's likely causing my symptoms?
• Other than the most likely cause, what are other possible causes for my symptoms?
• What tests do I need?
• What's the best course of action?
• What are the alternatives to the primary approach you're suggesting?
• I have these other health conditions. How can I best manage them together?
• Are there restrictions I need to follow?
• Should I see a specialist?
• Are there brochures or other printed material I can have? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor is likely to ask you several questions, such as:

• When did your symptoms begin?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?