Colorectal cancer symptoms may be minor or non-existent during the early stages of the disease, although there may be some early warning signs. The symptoms of colorectal cancer may not develop until the disease has progressed into stage II or beyond. Regular screening tests for cancer of the colon or rectum, especially with a colonoscopy, is recommended as part of a health plan for those over 50 years old or those under 50 who are at high risk or have a family history of the disease or other cancers. Talk with your doctor about when you should start regular colorectal cancer screening.
Several tests may be used to diagnose colorectal cancer. These tests may include a colonoscopy, or other endoscopic procedures, stool tests, or other lab tests, or an MRI, CT scan or PET/CT scan. In many cases, a biopsy may be required. These imaging and laboratory tests may also be used to track the size of tumors and monitor response to treatment.
Early warning signs of colorectal cancer
Most cancers in the colon or rectum develop from polyps, so screening to find and remove them when they first form helps prevent them from growing into cancers.
If early-stage colorectal cancer does cause symptoms, early warning signs may include sudden weight loss and/or narrow, ribbon-like stools. Other common early warning signs of colorectal cancer include:
- Rectal bleeding, either bright or dark red in color
- Narrow stools
- Tenesmus, which is the feeling that you have to empty your bowel but nothing passes
- Anemia caused by iron deficiency
- Persistent abdominal pain
- Unexplained weight loss
Although these symptoms may be caused by other, less serious conditions, such as hemorrhoids, ulcers and Crohn’s disease, they should be discussed with a doctor. Blood in the stool, even if it only appears intermittently, should never be ignored.
Local symptoms of colorectal cancer
Local symptoms are those that affect only the colon and/or rectum and have not spread to distant organs. Common local symptoms include:
- Alternating diarrhea and constipation, or other changes in bowel habits
- Rectal bleeding or blood in the stool
- Abdominal bloating, cramps, or discomfort
- A feeling that the bowel doesn’t empty completely
- Stools that are thinner than normal
If you experience these possible symptoms of colorectal cancer for an extended period of time, it is important that you visit a health care professional.
Systemic symptoms of colorectal cancer
Systemic colorectal cancer symptoms may impact more than the digestive tract and affect your entire body. Common systemic symptoms of colorectal cancer include:
- Unexplained loss of appetite
- Unexplained weight loss
Colon cancer symptoms
During stage I of colon cancer, no obvious signs or symptoms may have developed. As symptoms develop, they may vary depending on the tumor’s size and location in the large intestine. Early symptoms may affect only the colon and result in changes in bowel habits. As the cancer grows, it may spread, producing systemic symptoms that affect your whole body, such as fatigue and weight loss. Some changes in bowels habits that may be considered colon cancer signs include:
- Change in frequency of bowel movements
- Change in consistency of stool (loose or watery stools)
- Blood in stools (either as bright red spots or dark tar-like stools)
- Rectal bleeding
- Abdominal pain, bloating, or cramps
- A persistent feeling that you cannot completely empty your bowels
Rectal cancer symptoms
The symptoms of rectal cancer may be similar to those of other bowel diseases, such as ulcerative colitis or Crohn’s disease. But while symptoms of inflammatory bowel disease may subside during periods of remission, rectal cancer symptoms may be more severe and persistent as cancer develops. Tumors in the rectum may change the consistency, shape, or frequency of bowel movements. Symptoms may increase and become more severe as cancer spreads throughout the rectum or possibly into the colon. Rectal cancer signs related to bowel habits may include:
- An inability to completely empty the bowel
- Bloody stool
- Change in the size or shape of stools
Metastatic colorectal cancer symptoms
Patients with metastatic colorectal cancer may not always notice symptoms before a diagnosis. Metastatic colorectal cancer symptoms may depend on the size of the tumor or tumors and where cancer has spread outside the colon or rectum. For instance:
If the bones are affected, symptoms may include pain, fractures, constipation, and/or high calcium levels.
If the lungs are affected, symptoms may include shortness of breath, difficulty breathing, coughing, pain, and/or fatigue.
If the liver is affected, symptoms may include nausea, fatigue, swelling of the feet and hands, increased abdominal girth, and/or jaundice.
If the lymph nodes of the abdomen are affected, it may cause bloating, a swollen belly, and/or loss of appetite.
If the brain and/or spinal cord are affected, symptoms may include pain, confusion, memory loss, headache, blurred or double vision, difficulty speaking, and/or seizures.