Constipation, or changes in bowel habits (diarrhea, narrow stools, incomplete emptying), can be a symptom of any stage of colon cancer, from early-stage (Stage 1-3) as a sign of a tumor growing and obstructing the colon, to more severe in Stage 4 (metastatic) when it causes significant blockages or affects bowel function, sometimes with severe pain, nausea, and vomiting as waste backs up. It's a key indicator that a tumor is physically changing the colon's ability to pass stool, often presenting as persistent changes rather than temporary issues.
Symptoms of colon cancer can include: A change in bowel habits, such as more frequent diarrhea or constipation. Rectal bleeding or blood in the stool. Ongoing discomfort in the belly area, such as cramps, gas or pain.
Stage 4 colon cancer can change how your digestive system works in many ways. Some patients have constipation that lasts a long time, while others have diarrhea that doesn't go away. Stools can get thin, narrow, or hard to pass. Some people may see blood in their stool or stool that looks like dark tar.
Symptoms of stage 4 colon cancer that has spread to the liver include:
Diarrhea, constipation and abdominal pain are all symptoms of colorectal cancer. However, there are additional symptoms that are more concerning. “Sudden and unexplained weight loss, rectal bleeding or blood in the stool are all cause for concern,” says Richards.
Both conditions affect the digestive system, but in very different ways. Constipation is usually temporary and linked to lifestyle habits, while colon cancer is a life‑threatening disease that often develops silently over time.
Hard pebbles or nuggets that occur because of cancer-related constipation cause waste to remain in the colon longer and have more water removed from it. Dark brown or black color throughout caused by blood in the stool.
Colon cancer that has advanced to later stages can cause severe symptoms. Signs of late-stage colon cancer include: Persistent stomach pain or bloating – Tumors in the colon can cause a blockage that is painful and makes it hard to fully empty your bowels, making you feel full and bloated.
The "3-2-1 Rule" for colon cancer risk refers to the Amsterdam Criteria, a guideline to identify families potentially affected by Lynch Syndrome, a hereditary cancer predisposition, requiring: 3 or more relatives with Lynch-associated cancers, affecting 2 consecutive generations, with at least 1 relative diagnosed under age 50, and often with FAP excluded. It highlights family history red flags like multiple affected members, young diagnoses, and generational spread to prompt genetic counseling.
Symptoms of colorectal cancer may include:
Foods to Limit or Avoid
Red and Processed Meats: As we noted above, red meats (like beef, pork, and lamb) and processed meats (such as hot dogs, sausage, and lunch meats) have all been shown to raise colorectal cancer risk, as can the chemicals created from grilling, frying, or broiling them.
Once the cancer type has been identified, patients will have additional scans to determine the full extent of their disease. Then, they'll meet with a surgeon to discuss possible treatment plans.
Laxative. Laxatives may be used to help promote, or stimulate, bowel activity. Examples of laxatives that do this include senna or sennosides (Senokot), magnesium salts (Milk of Magnesia), mineral oil and lactulose.
The National Comprehensive Cancer Network, for example, recommends that people who are treated for stage II or III colon or rectal cancer have CEA testing every 3 to 6 months for 2 years and then every 6 months for 3 additional years, plus CT scans every 6 to 12 months for 5 years.
Fecal occult blood test (FOBT) and fecal immunochemical test (FIT) are lab tests used to check stool samples for hidden (occult) blood. The tests usually are repeated annually. The pros: Stool sample collection can be done at home.
Doctors use several diagnostic tests to determine the stage of colorectal cancer, so your staging may not be complete until all of your tests have been performed. Some of the tests your doctor may order include: Biopsy with pathology for tumor and lymph nodes. Blood work.
The 5-year relative survival rate for stage I colon cancer in the US is about 92%. The rate for stage IIA and stage IIB is 87% and 65%, respectively. Surprisingly, the 5-year survival rate for stage IIIA and stage IIIB are slightly higher at 90% and 72%, respectively.
Multiple genes are associated with hereditary colon cancer, but mutations in genes associated with Lynch syndrome (MLH1, MSH2, MSH6, PMS2, EPCAM) are the most common cause of the hereditary form of the disease. Prediction models can estimate an individual's risk for a Lynch syndrome mutation.
Constipation, diarrhea, and abdominal pain can all be symptoms of colorectal cancer. But they can also be signs of other conditions, including Crohn's disease, irritable bowel syndrome and even a stomach virus.
This research also indicates that once the cancer develops, there is a two-year window for it to metastasize. This process of cancer cells spreading to other parts of the body happens at a snail's pace — roughly ten years between the cancer cells starting to grow and the onset of symptoms.
Abdominal Pain and Bloating
Stomach bloating, distention, cramps or pain in the abdominal or bowel region can be symptoms of colon or rectal cancer.
Main symptoms of bowel cancer
Symptoms of bowel cancer may include: changes in your poo, such as having softer poo, diarrhoea or constipation that is not usual for you. needing to poo more or less often than usual for you. blood in your poo, which may look red or black.
Although bowel movement frequency varies greatly for each person, if more than three days pass without a bowel movement, the contents in the intestines may harden, making it difficult or even painful to pass. Straining during bowel movements or the feeling of incomplete emptying also may be considered constipation.
Stage 4 colon cancer
You may notice: Stools may be very thin or may look like pellets. Or you might not be able to pass stools at all. Blood in stools is common, and stools can be very dark.