Although the small bowel makes up three quarters of the digestive system, cancers in this area are rare. The information on this page is mainly about adenocarcinoma of the small bowel. Small bowel cancer, like all cancers, is not infectious and can’t be passed on to other people.
The small bowel
The small bowel is part of the digestive system and extends between the stomach and the large bowel (or colon). The small bowel is divided into three main parts: the duodenum, the jejunum and the ileum. The small bowel folds many times to fit inside your abdomen and is around 16 feet long. It is responsible for the breakdown of food, which allows vitamins, minerals and nutrients to be absorbed into the body.
Types of small bowel cancer
There are four main types of small bowel cancer and they are named after the cells where they develop. The types are: adenocarcinoma, sarcoma, neuroendocrone (carcinoid) tumors and lymphoma.
These tumors start in the lining of the bowel. They are the most common type of small bowel cancer and usually occur in the duodenum.
These tumors develop in the supportive tissues of the body. There are different types of sarcoma. Leiomyosarcomas usually grow in the muscle wall of the small bowel, most commonly in the ileum. Another rare type of sarcoma is a gastrointestinal stromal tumor (GIST), which can develop in any part of the small bowel.
Neuroendocrine (carcinoid) tumors
These start from cells that make hormones within the small bowel. These tumors appear most commonly in the ileum and sometimes within the appendix.
These tumors start in the lymph tissue of the small bowel. The lymph tissue is part of the body’s immune system. Usually small bowel lymphomas are non-Hodgkin lymphomas (NHLs). They occur most commonly in the jejunum or ileum. Occasionally, a small bowel cancer may be a secondary cancer. This means it has spread from a primary cancer somewhere else in the body.
Causes and risk factors of small bowel cancer
The cause of most small bowel cancers is unknown. However, some people with non-cancerous bowel conditions may have a higher risk of developing small bowel cancer. These conditions include Crohn’s disease, coeliac disease and Peutz-Jegher’s syndrome.
People who have had a cancer of the colon or rectum, or who have hereditary non-polyposis colorectal cancer (HNPCC) or familial adenomatous polyposis (FAP), also have an increased risk of developing small bowel cancer.
Small bowel cancer, like all cancers, is not infectious and can’t be passed on to other people.
Signs and symptoms of small bowel cancer
The symptoms of small bowel cancer are often vague and difficult to diagnose. They may include any of the following:
• dark or black stools due to bleeding in the small bowel
• cramping abdominal pain
• anemia (low number of red blood cells) due to blood loss
• weight loss
These symptoms may be caused by many things other than small bowel cancer but symptoms that are severe, get worse, or last for a few weeks should always be checked by your doctor.
Occasionally, the cancer can cause a blockage (obstruction) in the bowel, which may be complete or partial. The symptoms of this are vomiting, constipation, griping pain and a bloated feeling in the abdomen (tummy). Sometimes a blockage in the small bowel can cause the bowel to tear. This is a serious condition that usually occurs suddenly and needs to be treated with surgery. The symptoms include severe pain, shock (a drop in blood pressure) and abdominal swelling.
How small bowel cancer is diagnosed
Usually you’ll begin by seeing your PCP, who will examine you and arrange for any further tests that may be necessary. Your PCP will refer you to a hospital specialist for these tests and for expert advice and treatment.
At the hospital, the doctor will ask you about your general health and any previous medical problems. They will take blood samples to check for anemia and examine you to check that your liver is working properly. You may also have a chest x-ray to check your lungs and heart. You may be asked to take a sample of your stool (bowel movement) to the hospital so that it can be tested for blood. The following tests are commonly used to diagnose small bowel cancers.
Endoscopy or colonoscopy
These tests allow the doctor to look inside the duodenum and the upper part of the jejunum (endoscopy), or the lower part of the ileum (colonoscopy). The test may be done in the hospital’s outpatient department or on a ward. You will be asked to lie on your side and given a mild sedative to help you relax. The doctor gently passes a thin tube either down your throat and through your stomach (endoscopy), or into your back passage (colonoscopy). There is a light and lens at the end of the tube to help the doctor to see any abnormal areas. If necessary, a small sample of tissue will be taken (biopsy) for examination under a microscope by a pathologist. Unfortunately, these tests do not reach some areas of the jejunum or the ileum so different tests are needed to find tumors in these areas.
This test takes pictures of the whole of the inside of your digestive tract, including all of your small bowel. You swallow a capsule about the size of a large pill. Inside the capsule is a camera, a battery, a light and a transmitter. The camera takes two pictures a second for eight hours. The pictures are sent to a small recording device attached to a belt you wear round your waist. You have to follow a special diet the day before and on the day of the test. Your nurse or doctor will give you instructions about this. Otherwise you can carry on with your normal activities while the camera is taking pictures. About eight hours after swallowing the capsule you will need to return the recording device to the hospital. The pictures from the recorder are loaded onto a computer and will be looked at by your doctor. The capsule is disposable and is usually passed out naturally in bowel motions. If the capsule is not passed out of your system, you may need to have an operation to remove it.
This is a special x-ray of the small bowel, sometimes called a barium meal or barium follow-through. It is done in the hospital x-ray department. For this test it’s important that the bowel is empty so that a clear picture can be seen. Your hospital will give you instructions, but it is likely that on the day before your test you will be asked to take a laxative and drink plenty of fluids to help empty your bowel. On the day of your barium x-ray, you should have nothing to eat or drink. You will be asked to drink a fluid that contains barium, a substance that shows up white on an x-ray. The doctor will watch the barium pass through the whole of the small bowel on a screen, to look for any abnormalities. Your stools may be white for a couple of days after the test. This is the barium passing out of your body and is nothing to worry about. The barium can also cause constipation so you may need to take a mild laxative for a couple of days.
MRI (magnetic resonance imaging) scan
This test uses magnetism, instead of x-rays, to build up a detailed picture of areas of your body. Before the scan you may be asked to complete and sign a checklist. This is to make sure it’s safe for you to have an MRI scan. Before having the scan, you’ll be asked to remove any metal belongings, including jewelry. Some people are given an injection of dye into a vein in the arm. This is called a contrast medium and can help the images from the scan show up more clearly. During the test you will be asked to lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It’s painless but can be slightly uncomfortable, and some people feel a bit claustrophobic during the scan. It’s also noisy, but you’ll be given earplugs or headphones. You’ll be able to hear, and speak to, the person operating the scanner.
Sometimes it’s difficult to get a clear picture of the small bowel, and biopsies can’t always be taken, so diagnosis may be made during an operation.
Staging of small bowel cancer
The stage of a cancer is a term used to describe its size and whether it has spread beyond its original site. Knowing the type and stage of the cancer helps the doctors to decide on the best treatment. Cancer can spread in the body, either in the bloodstream or through the lymphatic system. The lymphatic system is part of the body’s defense against infection and disease. The system is made up of a network of lymph nodes that are linked by fine ducts containing lymph fluid. Your doctors will usually check the lymph nodes close to the small bowel to help find the stage of the cancer. There are four stages of small bowel cancer.
The cancer is contained within the lining of the small bowel or has spread into the muscle wall, but has not begun to spread to the lymph nodes or other parts of the body.
The cancer has spread through the muscle wall and may affect other nearby structures such as the pancreas.
The cancer has spread to nearby lymph nodes.
The cancer has spread to nearby lymph nodes and also to other parts of the body such as the liver or lungs.
If the cancer comes back after initial treatment this is known as recurrent cancer.