Rectal Cancer Signs What Causes Them and When to See a Doctor
Learn about the signs of rectal cancer, what causes them, and when to seek medical advice. Understand risk factors, prevention, and the importance of early detection.
Introduction
Noticing a change in your bathroom habits or a spot of blood can be alarming. While often linked to common conditions such as haemorrhoids, these changes can sometimes be the first signs of rectal cancer. Understanding what leads to these signs is the first step towards proactive health.
Rectal cancer develops in the last several inches of the large intestine, and its onset is typically a slow process influenced by a combination of genetics, lifestyle, and environmental factors. This article will demystify the causes behind rectal cancer, detail the symptoms you should never ignore, and outline modern diagnostic and prevention strategies. Knowledge is power, and recognising these factors empowers you to take charge of your digestive health.
Understanding Rectal Cancer: A Brief Overview
Rectal cancer is a type of colorectal cancer that begins in the rectum, the final 6–8 inches of the large intestine that serves as a temporary storage site for stool before it is expelled. It arises when cells in the rectum’s lining develop mutations in their DNA. These mutated cells grow and divide uncontrollably, forming a tumour that can invade nearby tissues and, over time, spread (metastasise) to other parts of the body.
While the terms are often used interchangeably, it is crucial to understand the anatomical distinction, as it influences treatment options.
Rectum vs. Colon: What’s the Difference?
The colon and rectum are both parts of the large intestine but have different structures and functions. The colon is a longer, muscular tube that absorbs water and electrolytes from digested food. The rectum is a shorter, chamber-like structure that holds stool.
This key difference means surgeries for rectal cancer are often more complex due to its location in the tight confines of the pelvis and its close proximity to other nerves and organs.
The Primary Triggers: What Leads to Rectal Cancer
The development of rectal cancer is rarely due to a single cause. It is usually a combination of various risk factors accumulating over time.
Genetic and Unavoidable Risk Factors
Some risks are inherent and cannot be changed. However, knowing them allows for heightened vigilance and earlier screening.
Age and Family History
The risk of developing rectal cancer increases significantly after age 50. Furthermore, having a first-degree relative (parent, sibling, or child) with colorectal cancer doubles or even triples your risk, pointing to a potential genetic or shared environmental component.
Inherited Genetic Syndromes (Lynch Syndrome, FAP)
About 5–10% of cases are linked to specific inherited syndromes. Lynch Syndrome (hereditary non-polyposis colorectal cancer or HNPCC) is the most common and dramatically increases the risk of colorectal and other cancers. Familial Adenomatous Polyposis (FAP) is rarer and causes hundreds of polyps to develop in the colon and rectum, often at a very young age, with a near 100% risk of cancer if not treated.
Consult an Oncologist for Personalised Advice
Lifestyle and Modifiable Risk Factors
This category offers the greatest opportunity for risk reduction. Your daily choices play a monumental role.
The Red and Processed Meat Connection
Numerous studies, including one from the American Institute for Cancer Research, strongly link high consumption of red meat (beef, pork, lamb) and processed meats (hot dogs, bacon, sausages, deli meats) to an increased risk of colorectal cancer. Cooking these meats at high temperatures can produce carcinogens such as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs).
Low Fibre, High Fat Diet
A diet lacking in fruits, vegetables, and whole grains (all high in fibre) can lead to constipation and slower transit time. This means potential carcinogens in waste stay in contact with the rectal lining for longer. A high-fat diet may also alter gut bacteria (the microbiome) in ways that promote inflammation and cancer growth.
Smoking and Alcohol Consumption
Tobacco smoke is a known carcinogen that enters the bloodstream and can damage cells throughout the body, including the rectum. Similarly, heavy alcohol consumption (more than three drinks per day) can irritate the digestive tract and hinder the body’s ability to absorb essential nutrients such as folate, which helps protect DNA.
Sedentary Lifestyle and Obesity
Physical inactivity and being overweight are consistently linked to a higher risk. Obesity, particularly around the waist, leads to chronic inflammation and higher levels of insulin and related growth factors in the body, which may encourage cancer cell growth.
From Healthy Cell to Cancer: The Biological Process
The journey to cancer often begins with a precancerous polyp, most commonly an adenoma. The rectal cancer development process is slow, taking 10–15 years. It starts with a genetic mutation in a single cell lining the rectum. This cell ignores signals to stop dividing and begins forming a small cluster of abnormal cells—a polyp.
Over years, additional mutations can occur within the polyp. Eventually, these cells may gain the ability to invade through the layers of the rectal wall and into blood vessels or lymph nodes, allowing them to travel to distant organs. This is why screening colonoscopies are so effective; they find and remove polyps before they become cancerous.
Recognising the Signs and Symptoms of Rectal Cancer
Early-stage rectal cancer often causes no symptoms. When they do appear, they are frequently mistaken for other conditions.
Early Warning Signs Often Missed
• A persistent change in bowel habits: diarrhoea, constipation, or a change in stool consistency that lasts more than a few days.
• Rectal bleeding or blood in the stool: bright red blood is a common sign, but often attributed to haemorrhoids. Any rectal bleeding should be evaluated by a doctor.
• Abdominal discomfort: frequent gas, bloating, cramps, or pain.
• The feeling of incomplete evacuation: the sensation that you still need to pass a bowel movement even after you have just had one.
Symptoms as the Cancer Progresses
• Unexplained weakness or fatigue, often caused by anaemia from slow, chronic blood loss.
• Unintended weight loss, as cancer cells consume energy and alter metabolism.
• Narrow or ribbon-like stool, due to a tumour physically narrowing the passageway.
• Persistent abdominal pain or pain during bowel movements.
If you experience any of these symptoms, especially rectal bleeding or a persistent change in bowel habits, it is crucial to consult a healthcare professional for an accurate diagnosis.
How is Rectal Cancer Diagnosed?
If symptoms suggest rectal cancer, doctors will recommend tests to confirm it.
The Gold Standard: Colonoscopy and Biopsy
A colonoscopy is the most comprehensive test. A doctor uses a long, flexible tube with a camera to examine the entire rectum and colon. If any suspicious areas or polyps are found, they can be removed or biopsied during the procedure. A pathologist then examines the biopsy under a microscope to check for cancer cells.
Imaging Tests: CT, MRI, and PET Scans
Once cancer is diagnosed, imaging tests are used to determine its stage—how deep it has grown and if it has spread. A pelvic MRI is particularly important for rectal cancer to see the detailed anatomy of the pelvis. A CT scan of the chest, abdomen, and pelvis checks for distant metastasis.
Prevention: Can You Reduce Your Risk?
While you cannot change your genetics, you can dramatically influence your modifiable risk factors:
• Get Screened: Follow recommended screening guidelines starting at age 45 (or earlier if you have a family history or other risk factors).
• Eat a Balanced Diet: Focus on fruits, vegetables, and whole grains. Limit red and processed meats.
• Exercise Regularly: Aim for at least 30 minutes of moderate activity most days.
• Maintain a Healthy Weight.
• Do Not Smoke and Limit Alcohol.
Conclusion
Understanding what leads to the signs of rectal cancer is a powerful tool for safeguarding your health. The journey from a healthy cell to cancer is complex, involving a mix of genetic predisposition and lifestyle choices.
While we cannot control our genetics, we have significant agency over factors such as diet, exercise, and adherence to screening schedules. Recognising the symptoms—especially rectal bleeding or a persistent change in bowel habits—and taking them seriously is critical.
Early detection through screening colonoscopy remains the gold standard, often allowing for the removal of precancerous polyps before they turn into cancer. If you have any concerns or fall into a higher-risk category, do not hesitate to take action. Your health is your greatest asset; protect it by staying informed and proactive.
Consult an Oncologist for Personalised Advice
Consult an Oncologist for Personalised Advice
Dr. Gopal Kumar
Head, Neck and Thyroid Cancer Surgeon
15 Years • MBBS, MS , FARHNS ( Seoul, South Korea ), FGOLF ( MSKCC, New York )
Delhi
Apollo Hospitals Indraprastha, Delhi
(25+ Patients)
Dr. Sanchayan Mandal
Medical Oncologist
17 Years • MBBS, DrNB( MEDICAL ONCOLOGY), DNB (RADIOTHERAPY),ECMO. PDCR. ASCO
Kolkata
MCR SUPER SPECIALITY POLY CLINIC & PATHOLOGY, Kolkata
Dr. Rupam Manna
Radiation Specialist Oncologist
4 Years • MBBS MD(RADIO THERAPY)
Barasat
Diab-Eat-Ease, Barasat
Dr.sanchayan Mandal
Medical Oncologist
17 Years • MBBS, DrNB( MEDICAL ONCOLOGY), DNB (RADIOTHERAPY),ECMO. PDCR. ASCO
Kolkata
Dr. Sanchayan Mandal Oncology Clinic, Kolkata
Dr Gowshikk Rajkumar
Oncologist
10 Years • MBBS, DMRT, DNB in Radiation oncology
Bengaluru
Apollo Clinic, JP nagar, Bengaluru
Consult an Oncologist for Personalised Advice
Dr. Gopal Kumar
Head, Neck and Thyroid Cancer Surgeon
15 Years • MBBS, MS , FARHNS ( Seoul, South Korea ), FGOLF ( MSKCC, New York )
Delhi
Apollo Hospitals Indraprastha, Delhi
(25+ Patients)
Dr. Sanchayan Mandal
Medical Oncologist
17 Years • MBBS, DrNB( MEDICAL ONCOLOGY), DNB (RADIOTHERAPY),ECMO. PDCR. ASCO
Kolkata
MCR SUPER SPECIALITY POLY CLINIC & PATHOLOGY, Kolkata
Dr. Rupam Manna
Radiation Specialist Oncologist
4 Years • MBBS MD(RADIO THERAPY)
Barasat
Diab-Eat-Ease, Barasat
Dr.sanchayan Mandal
Medical Oncologist
17 Years • MBBS, DrNB( MEDICAL ONCOLOGY), DNB (RADIOTHERAPY),ECMO. PDCR. ASCO
Kolkata
Dr. Sanchayan Mandal Oncology Clinic, Kolkata
Dr Gowshikk Rajkumar
Oncologist
10 Years • MBBS, DMRT, DNB in Radiation oncology
Bengaluru
Apollo Clinic, JP nagar, Bengaluru
Frequently Asked Questions
1. Is bright red blood always a sign of rectal cancer?
No, bright red blood is most commonly caused by haemorrhoids or anal fissures. However, it is the most common early sign of rectal cancer and should never be self-diagnosed. Any instance of rectal bleeding warrants a consultation with a doctor.
2. What’s the difference between rectal cancer and colon cancer?
The primary difference is location within the large intestine. Colon and rectal cancer, collectively known as colorectal cancer, are similar but their location affects treatment. Rectal cancer, due to its position in the pelvis, can be more challenging to treat surgically and often involves a combination of radiation and chemotherapy before surgery.
3. At what age should I start getting screened for rectal cancer?
The general guideline is to begin regular screening at age 45. However, if you have a family history of rectal cancer or other risk factors such as inflammatory bowel disease (IBD) or a known genetic syndrome, you may need to start much earlier. Discuss your personal risk with your doctor.
4. Can a healthy lifestyle completely prevent rectal cancer?
While a healthy lifestyle significantly reduces your risk, it cannot eliminate it entirely due to factors such as genetics and age. However, combining a balanced diet, regular exercise, avoiding tobacco, and limiting alcohol with recommended screenings is the most effective strategy for prevention and early detection.
5. I have haemorrhoids. Does that increase my risk of getting cancer?
No, having haemorrhoids does not increase your risk of developing rectal cancer. However, the symptoms can be similar (especially bleeding), which is why it is essential to have a doctor confirm the cause of your symptoms and rule out anything more serious.