Overview

The rectum is the last several inches of the large intestine. It starts at the end of the final segment of your colon and ends when it reaches the short, narrow passage leading to the anus.

Cancer inside the rectum (rectal cancer) and cancer inside the colon (colon cancer) are often referred to together as "colorectal cancer."

While rectal and colon cancers are similar in many ways, their treatments are quite different. This is mainly because the rectum sits in a tight space, barely separated from other organs and structures in the pelvic cavity. As a result, complete surgical removal of rectal cancer is challenging and highly complex. Additional treatment is often needed before or after surgery — or both — to reduce the chance that the cancer will return.

In the past, long-term survival was uncommon for people with rectal cancer, even after extensive treatment. Thanks to treatment advances over the past 30 years, rectal cancer can now, in many cases, be cured.

Mayo Clinic's approach to rectal cancer care

Source: http://www.mayoclinic.com

Symptoms

Common symptoms include:

• A change in your bowel habits, such as diarrhea, constipation or more-frequent bowel movements
• Dark or red blood in stool
• Mucus in stool
• Narrow stool
• Abdominal pain
• Painful bowel movements
• Iron deficiency anemia
• A feeling that your bowel doesn't empty completely
• Unexplained weight loss
• Weakness or fatigue

When to see a doctor

Make an appointment with your doctor if you have symptoms suggesting rectal cancer, particularly blood in your stool or unexplained weight loss.

Source: http://www.mayoclinic.com

Causes

Rectal cancer occurs when healthy cells in the rectum develop errors in their DNA. In most cases, the cause of these errors is unknown.

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 the cells accumulate, they form a tumor.

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

Inherited gene mutations that increase the risk of colon and rectal cancer

In some families, gene mutations passed from parents to children increase the risk of colorectal cancer. These mutations are involved in only a small percentage of rectal cancers. Some genes linked to rectal cancer increase an individual's risk of developing the disease, but they don't make it inevitable.

Two well-defined genetic colorectal cancer syndromes are:

• Hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC, also called Lynch syndrome, increases the risk of colon cancer and other cancers. People with HNPCC tend to develop colon cancer before age 50.
• Familial adenomatous polyposis (FAP). FAP is a rare disorder that causes you to develop thousands of polyps in the lining of your colon and rectum. People with untreated FAP have a greatly increased risk of developing colon or rectal cancer before age 40.

FAP, HNPCC and other, rarer inherited colorectal cancer syndromes can be detected through genetic testing. If you're concerned about your family's history of colon cancer, talk to your doctor about whether your family history suggests you have a risk of these conditions.

Source: http://www.mayoclinic.com

Diagnosis

Rectal cancer is often diagnosed when a doctor orders tests to find the cause of rectal bleeding or iron deficiency anemia. A colonoscopy is the most accurate of these tests. In a colonoscopy, a doctor uses a thin, flexible, lighted tube with a video camera at its tip (a colonoscope) to view the inside of your colon and rectum.

Sometimes rectal cancer has no noticeable symptoms. People without symptoms may learn they have rectal cancer when they have a screening colonoscopy — that is, a colonoscopy recommended at age 50 for everyone with an average risk of colorectal cancer.

It's usually possible to remove small tissue samples (biopsies) from suspicious-looking areas during a colonoscopy. Laboratory analysis of this tissue helps pin down the diagnosis.

Staging rectal cancer

Once you are diagnosed with rectal cancer, the next step is to determine the cancer's extent (stage). Staging helps guide decisions about the most appropriate treatments for you. The following blood tests and imaging studies are involved in staging rectal cancer:

• Complete blood count (CBC). This test reports the numbers of different types of cells in your blood. A CBC shows whether your red blood cell count is low (anemia), which suggests that a tumor is causing blood loss. A high level of white blood cells is a sign of infection, which is a risk if a rectal tumor grows through the wall of the rectum.
• Carcinoembryonic antigen (CEA). Cancers sometimes produce substances called tumor markers that can be detected in blood. One such marker, carcinoembryonic antigen (CEA), may be higher than normal in people with colorectal cancer. CEA testing is particularly useful in monitoring your response to treatment.
• Chemistry panel. This test measures a number of chemicals in the blood. Abnormal levels of some of these chemicals may suggest that cancer has spread to the liver. High levels of other chemicals may indicate problems with other organs, such as the kidneys.
• CT (computed tomography) scan of the chest. This imaging test helps determine whether rectal cancer has spread to other organs, such as the liver and lungs.
• MRI (magnetic resonance imaging) of the pelvis. An MRI provides a detailed image of the muscles, organs and other tissues surrounding a tumor in the rectum. An MRI also shows the lymph nodes near the rectum and different layers of tissue in the rectal wall.

Rectal cancer stages

Rectal cancers fall into one of five possible stages (stage 0 through stage 4). The stages, in simplified form, are:

• Stage 0. Cancer cells on the surface of the rectal lining (mucosa), sometimes within a polyp
• Stage I. Tumor extending below the rectal mucosa, sometimes penetrating into the rectal wall
• Stage II. Tumor extending into or through the rectal wall, sometimes reaching and growing on or sticking to tissues next to the rectum
• Stage III. Tumor invading lymph nodes next to the rectum, as well as structures and tissues outside the rectal wall
• Stage IV. Tumor spread to a distant organ or lymph nodes distant from the rectum

Staging also involves examining a sample of tissue taken from the tumor (a biopsy) to determine the tumor's grade. Low-grade tumors tend to grow and spread slowly. In contrast, high-grade tumors grow and spread quickly, so they may need more-aggressive treatment.

Source: http://www.mayoclinic.com

Prevention

Talk to your doctor about when you should start getting screened for colorectal cancer. Guidelines generally recommend having your first colorectal cancer screening test at age 50. Your doctor may recommend more-frequent or earlier screening if you have other risk factors, such as a family history of colon or rectal cancer.

The most accurate screening test is a colonoscopy. In this test, a doctor examines the lining of your rectum and large intestine using a long, flexible tube with a tiny video camera at its tip (colonoscope). The colonoscope is inserted in the anus and advanced through the rectum and colon. As the scope's camera moves through the bowel, it sends a video of the rectal and colonic lining to a monitor the doctor sees. If a polyp or suspicious-looking area of tissue is found, the doctor can also take samples of tissue from these areas with instruments inserted in the colonoscope.

Risk factors

The characteristics and lifestyle factors that increase your risk of rectal cancer are the same as those that increase your risk of colon cancer. They include:

• Older age. The great majority of people diagnosed with colon and rectal cancer are older than 50. Colorectal cancer can occur in younger people, but it occurs much less frequently.
• African-American descent. People of African ancestry born in the United States have a greater risk of colorectal cancer than do people of European ancestry.
• A personal history of colorectal cancer or polyps. If you've already had rectal cancer, colon cancer or adenomatous polyps, you have a greater risk of colorectal cancer in the future.
• Inflammatory bowel disease. Chronic inflammatory diseases of the colon and rectum, such as ulcerative colitis and Crohn's disease, increase your risk of colorectal cancer.
• Inherited syndromes that increase colorectal cancer risk. Genetic syndromes passed through generations of your family can increase your risk of colorectal cancer. These syndromes include FAP and HNPCC.
• Family history of colorectal cancer. You're more likely to develop colorectal cancer if you have a parent, sibling or child with the disease. If more than one family member has colon cancer or rectal cancer, your risk is even greater.
• Dietary factors. Colorectal cancer may be associated with a diet low in vegetables and high in red meat, particularly when the meat is charred or well-done.
• A sedentary lifestyle. If you're inactive, you're more likely to develop colorectal cancer. Getting regular physical activity may reduce your risk of colon cancer.
• Diabetes. People with poorly controlled type 2 diabetes and insulin resistance may have an increased risk of colorectal cancer.
• Obesity. People who are obese have an increased risk of colorectal cancer and an increased risk of dying of colon or rectal cancer when compared with people considered normal weight.
• Smoking. People who smoke may have an increased risk of colon cancer.
• Alcohol. Regularly drinking more than three alcoholic beverages a week may increase your risk of colorectal cancer.
• Radiation therapy for previous cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colorectal cancer.

Source: http://www.mayoclinic.com