AI Summary Overview
Quick Glance: Common Colon Cancer Symptoms
Possible symptoms of colon cancer may include:
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Persistent alteration in bowel habits
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A noticeable change in normal bowel habits
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Blood in stool or rectal bleeding
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Persistent abdominal pain, cramping or bloating
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Feeling that the bowel has not completely emptied
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Unexplained weight loss
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Breathlessness or paleness due to anaemia
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Unusual tiredness or weakness
Symptoms may vary according to the location and extent of the tumour. Besides, many other bowel conditions can cause similar symptoms.
Colon Cancer Symptoms That Should Not Be Ignored
Colon cancer symptoms need to be medically evaluated, especially when they persist, get worse or occur simultaneously. Some of these symptoms of colon cancer and what they may indicate are briefly described in the table below:
| Symptom | What It May Indicate? |
| Blood in the stool or rectal bleeding | Bleeding somewhere in the lower digestive tract that requires investigation |
| Persisting change in bowel habits for more than a few weeks | A change affecting normal movement of stool through the colon |
| Iron deficiency anaemia without any clear reason with fatigue | Slow, hidden blood loss from the digestive tract or another underlying cause |
| Persistent abdominal pain, cramping or fullness | A bowel condition requiring further assessment |
| Unexpected weight loss | A significant underlying illness, including possible cancer |
| Ongoing feeling that bowel emptying is incomplete | A persistent change in bowel function requiring evaluation |
| Increasing fatigue, paleness or breathlessness | Anaemia, which may result from chronic gastrointestinal blood loss |
Why Do Colon Cancer Symptoms Occur?
Symptoms of colon cancer can arise from a tumour that affects the lining or function of the large intestine. The tumour may bleed slowly, which can lead to iron-deficiency anaemia and symptoms such as tiredness, weakness or breathlessness.
As a tumour grows, it can change how stool moves through the colon, leading to constipation, diarrhoea, altered stool shape, abdominal discomfort or a feeling of incomplete emptying. A larger tumour may occasionally narrow or block the bowel, causing increasing abdominal swelling, pain and vomiting.
Colon Cancer Symptoms That Require Immediate Medical Attention
It is recommended to visit a doctor immediately if you notice any or multiple of the following symptoms of colon cancer:
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Severe abdominal pain combined with the swelling or rigidity of the abdomen
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Continuous vomiting with or without abdominal swelling
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An inability to defecate or pass gas (bowel obstruction)
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Heavy or persistent rectal bleeding or tarry stools
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Dizziness, fainting, or weakness caused by heavy blood loss
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Sudden severe abdominal pain with a rigid or very tender abdomen
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Fever with severe abdominal pain and rapidly worsening illness
Symptoms of Colon Cancer Based on Type
The type of colon cancer depends on the location of the tumour inside the colon. Various types of colon cancer and their characteristic symptoms are mentioned in the table below:
| Type | Symptom |
| Adenocarcinoma | Abdominal pain, presence of blood in the stool, alteration in bowel movements, pencil-like stools and unexplained weight loss |
| Gastrointestinal carcinoid tumour (rare) | Abdominal pain or cramps, bloating, tiredness, and weight loss; rectal tumours may also present with pain, blood in stool or constipation |
| Primary colorectal lymphoma (rare) | Indigestion, bloating, abdominal pain, vomiting, diarrhoea and weight loss |
| Gastrointestinal stromal tumour (GIST) (rare) | GI bleeding, abdominal pain, lump, nausea, vomiting, decreased appetite, weight loss, and weakness or tiredness |
| Leiomyosarcoma (rare) | Fatigue, weight loss, alterations in stool, vomiting of blood and other digestive problems |
| Squamous cell carcinoma (very rare) | Symptoms will differ based on the tumour location and may involve bowel or abdominal symptoms |
Can You Have Colon Cancer Without Symptoms?
Yes. Colon cancer can cause few or no noticeable symptoms, particularly when the tumour is small or at an early stage. Symptoms may become more noticeable as the cancer grows. Colorectal screening is specifically intended to detect cancer or precancerous polyps in people who do not have symptoms.
When Can Colon Cancer Symptoms Become Life-Threatening?
Colon cancer can become life-threatening when it causes severe bleeding, bowel obstruction, perforation or serious infection. Some of these symptoms and why they are considered serious are listed in the table below:
| Symptoms | Why It Is Serious |
| Severe cramping abdominal pain, marked bloating, vomiting and inability to pass stool or gas | These symptoms may indicate complete bowel obstruction, which requires urgent treatment. |
| Sudden severe abdominal pain with a rigid or very tender abdomen | A perforation of the bowel can allow intestinal contents to leak into the abdomen and cause peritonitis. |
| Heavy rectal bleeding with dizziness, fainting, rapid heartbeat or extreme weakness | Significant gastrointestinal blood loss can cause circulatory instability or severe anaemia. |
| High fever, confusion or rapid deterioration with severe abdominal pain | These symptoms may indicate severe infection or sepsis following an abdominal complication. |
How are Colon Cancer Symptoms Diagnosed?
Doctors may suggest certain diagnostic tests if there is a possibility of colon cancer. An overview of colon cancer diagnostic methods and their purpose are described in the table below:
| Diagnostic Test or Assessment | Purpose |
| Medical history and physical examination | Reviews bowel changes, bleeding, abdominal symptoms, weight loss and personal or family cancer history |
| Complete blood count (CBC/FBC) | Checks for anaemia that may result from chronic blood loss |
| Iron studies | Help determine whether anaemia is caused by iron deficiency |
| Colonoscopy | Examines the inside of the colon and allows suspicious tissue to be sampled |
| Biopsy and histopathology | Confirms whether suspicious tissue contains cancer cells |
| CT scan | Assesses the extent of confirmed cancer and whether it has spread to other areas |
| MRI | Used in selected situations; it is particularly important for local assessment of rectal rather than routine colon cancer |
| CEA blood test | May provide prognostic information and assist with monitoring after diagnosis; it does not confirm colon cancer |
FAQs
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Q1. What is the first symptom of colon cancer?
Ans: The first symptom of colon cancer may include changes in bowel habits, blood in the stool or fatigue due to anaemia. -
Q2. Can colon cancer develop without symptoms?
Ans: Yes. Colon cancer can occur without noticeable symptoms, particularly in the early stages, and may only be detected through colorectal cancer screening. -
Q3. Can colon cancer cause changes in bowel habits?
Ans: Yes. Colon cancer can cause persistent diarrhoea, constipation, altered stool shape or a feeling that the bowel has not emptied completely.
