Diagnosis & staging
The large intestine absorbs water and gets rid of waste for the body. It is the lower part of the gastrointestinal tract (digestive
The colon is the longest part of the large intestine. It is a tube that is about 1.5 - 1.8 m (5 to 6 feet) long. It is often called the bowel.
The colon starts where the small intestine ends. There are four parts to the colon:
- Ascending colon goes up towards the liver
- Transverse colon crosses the abdomen
- Descending colon goes down the body
- Sigmoid colon is an s-shaped curve between the descending colon and the rectum.
The rectum is about 12 cm long (4.7 inches). It is between the sigmoid colon and the anal canal. The rectum holds stool (poop) until you have a bowel movement (go poop).
Image of colon and rectum
What are the signs and symptoms of colorectal cancer?
Many of the common symptoms of colorectal cancers can also be caused by other conditions.
These are some symptoms of colorectal cancer:
- A change in your bowel habits.
- Bowel obstruction (blockage of your bowel)
- Change in the size of your stool (poop)
- Constipation (you cannot go poop as often or as easily as you usually do)
- Diarrhea (loose or watery poop)
- Blood in your stool, either apparent (visible) or occult (hidden).
- Pain in your lower abdomen or pelvis.
- If the tumour has spread, it may cause enlargement of your liver, abdominal bloating, pain in your lower back, or bladder symptoms such as increased urinary frequency (you go pee more often than is normal for you) or blood in your urine.
- One out of twenty people with this cancer may develop sudden obstruction of the bowel or a perforation (tear) in their bowel.
- Anemia (low iron in your blood)
- Feeling very tired
- Nausea or vomiting
- Weight loss and weakness
If you have any signs or symptoms that you are worried about, please talk to your family doctor or nurse practitioner.
How is colorectal cancer diagnosed?
Tests that may help diagnose colorectal cancer include:
- General physical exam including a digital rectal examination (a doctor or nurse practitioner puts their finger in your bum to examine you).
- Lab and blood tests
- Testing of stool sample for occult (hidden) blood.
- Barium enema X-ray: A special liquid is put into your colon by enema (a tube is used to inject the liquid into your rectum and colon). Then, X-rays are taken.
- Sigmoidoscopy: a thin, lighted tube with a camera is put into your anus and then gently pushed into the rectum and lower colon. Doctors can examine the lowest 50 cm (20 inches) of the colon in this way. They can also use this scope to grab tiny bits of tissue to look at under the microscope.
- Colonoscopy: This is similar to a sigmoidoscopy but doctors can look at both the upper and lower colon.
- Biopsy of colon or rectal tissue: A doctor removes a small portion of the colon or rectum to examine under a microscope. This is the most accurate test of all, but because it involves cutting the body, the other tests are usually done first.
- CT (computed tomography) scan of abdomen and pelvis: to see the tumour and if the cancer has spread.
- Ultrasound of abdomen: to see the tumour.
more information on tests used to diagnose cancer, see BC Cancer Library screening and diagnosis pathfinder.
- Most cases of colon and rectal cancers are adenocarcinomas.
- Sometimes colon and rectal cancers are lymphomas, melanomas, sarcomas or squamous cell carcinomas
Staging describes the cancer. Staging is based on how much cancer is in the body, where it was first diagnosed, if the cancer has spread and where it has spread to.
The stage of the cancer can help your health care team plan your treatment. It can also tell them how your cancer might respond to treatment and the chance that your cancer may come back (recur).
- Stage 1: Tumour (cancer growth) is only in the colon wall, not growing into the muscle in the wall. The cure rate for this stage is over 90% (more than 90 out of 100 people).
- Stage 2: Tumour has spread into the tissue surrounding the colon or has grown through the wall of the colon or rectum. The cure rate is about 70% (70 out of 100 people).
- Stage 3: Cancer is in the lymph nodes near the colon or rectum. The cure rate is about 50% (50 out of 100 people) depending on how many lymph nodes have cancer.
- Stage 4: Cancer has spread to other parts of the body (distant metastasis) or the cancer has spread into other organs. This type of cancer is often not curable. There are treatments that to help with symptoms, improve the quality of life and significantly extend life.
The grade of the cancer describes how different the cancer cells look from normal cells and how fast the cancer cells are growing. A pathologist will give the cancer a grade after looking at the cells under a microscope.
Colorectal cancer can be grade 1, 2, 3 or 4. The lower the number, the lower the grade.
Low grade: cells are abnormal but look a lot like normal cells. Low grade cancers usually grow slowly and are less likely to spread.
High grade: cells are abnormal and do not look like normal cells. High grade cancers usually grow more quickly and are more likely to spread.
The grade of the cancer helps your health care team plan your treatment.