Colorectal cancer — symptoms worth knowing and when should you undergo a colonoscopy?

Editorial preparation: Wyspa Medycyny Przyjaznej Editorial Team · Medical consultation: Wyspa Medycyny Przyjaznej proctology and gastroenterology team — to be specified before publication · Medical review: to be confirmed before publication · Creation date: 10 July 2026 · Review date: to be completed after approval · Updated: 10 July 2026

This article is educational and does not replace a medical consultation or colonoscopy. Visible blood in the stool, rectal bleeding, unexplained anaemia, unintended weight loss, a persistent change in bowel habits, a positive faecal occult blood/FIT result or abdominal pain accompanied by deterioration in general health require medical diagnostics.

Key information at a glance

• Colorectal cancer may remain asymptomatic for a long time, which is why prevention is so important.
• Colonoscopy allows the whole large bowel to be examined, polyps to be detected, tissue samples to be collected and some precancerous lesions to be removed.
• Blood in the stool or rectal bleeding does not always mean cancer, but it should not automatically be attributed to haemorrhoids.
• Warning symptoms include blood in the stool, a change in bowel habits, alternating diarrhoea and constipation, weight loss, anaemia, mucus in the stool, abdominal pain, weakness and a positive FIT/faecal occult blood test.
• In Poland, the colonoscopy screening programme is intended for asymptomatic people aged 50–65, or aged 40–49 if a first-degree relative had colorectal cancer, provided they have not undergone colonoscopy in the previous 10 years.
• If you have symptoms, do not wait only for the screening programme. Symptoms require diagnostics regardless of age.
• A proctologist assesses the anus and anal canal, may perform anoscopy and determine whether the problem is local. Colonoscopy is needed when the entire large bowel must be assessed.
• Colorectal polyps often cause no symptoms, but some may develop into cancer over time. Detecting and removing them therefore has preventive value.
• A positive FIT or faecal occult blood result does not automatically mean cancer, but it requires further diagnostics, usually colonoscopy.

Who can provide medical authorship for this blog?

The safest option is to label the text as editorial content reviewed by the WMP proctology and gastroenterology team. Once a specific person is selected, medical co-authorship may be assigned to a doctor who deals with proctological symptoms, for example Justyna Szul, MD, Sara Godyńska, MD, Kamil Smok, MD, or a gastroenterologist — after confirming their scope of competence and obtaining approval before publication.

Does this topic make sense for SEO, AI and Google Search?

Yes. Patients very often search for answers to questions such as: “colorectal cancer symptoms”, “blood in stool is it cancer”, “rectal bleeding haemorrhoids or cancer”, “when should I have a colonoscopy”, “colonoscopy after 50”, “colorectal cancer screening programme”, “colon polyps”, “change in bowel habits”, “positive FIT what next” and “can a proctologist detect bowel cancer”. This is a high-intent health topic that should be written carefully, without frightening patients but also without giving false reassurance.

In oncology topics, E-E-A-T is particularly important: a medical author or reviewer, update date, sources, warning symptoms, distinction between prevention and symptom-based diagnostics, and clear information about when a patient should see a doctor. This blog should direct patients towards appropriate diagnostics, not replace a consultation or colonoscopy.

Colorectal cancer — why can the symptoms be misleading?

Colorectal cancer may develop slowly. Some cancers arise from polyps that may cause no symptoms for a long time. A patient may therefore feel well, have a normal appetite and experience no pain even though a lesion requiring treatment is developing in the bowel.

When symptoms appear, they are often non-specific. Bleeding may be attributed to haemorrhoids, diarrhoea to stress or diet, constipation to a “normal problem”, and weakness to overwork. This is why persistent, new or recurrent bowel symptoms require medical assessment.

The point is not to treat every symptom as cancer. The point is not to miss situations in which broader diagnostics are required rather than haemorrhoid cream, probiotics or dietary changes alone.

Colorectal cancer symptoms worth knowing

The symptoms of colorectal cancer depend on the location and stage of the lesion and on whether the tumour causes bleeding, narrowing of the bowel lumen or impaired passage. The most important symptoms include:

• blood in the stool — bright red, dark red, black and tarry, or only detectable by a faecal occult blood test,
• rectal bleeding, particularly if new, recurrent or unexplained,
• a change in bowel habits — new constipation, diarrhoea or alternating diarrhoea and constipation,
• a feeling of incomplete evacuation or persistent urge after passing stool,
• a change in stool shape, for example persistent narrowing of the stool,
• mucus in the stool, especially when accompanied by blood or a change in bowel habits,
• abdominal pain, bloating, gurgling or increasing discomfort,
• iron-deficiency anaemia, weakness, pallor, palpitations or shortness of breath,
• unintended weight loss,
• loss of appetite or deterioration in general wellbeing,
• a positive FIT or positive faecal occult blood result.

No single symptom confirms colorectal cancer. However, symptoms that are new, persistent, recurrent or worsening should be taken seriously.

Blood in the stool — haemorrhoids, an anal fissure or colorectal cancer?

Bright-red blood on toilet paper or on the stool often comes from the anal area, for example from haemorrhoids, an anal fissure or irritation. This does not mean that every episode of bleeding can safely be assumed to be haemorrhoids. Bleeding is a symptom, not a diagnosis.

A proctologist can assess the anus, anal canal and lower rectum. Digital rectal examination and anoscopy may be helpful. However, when bleeding is unexplained or recurrent, or is accompanied by a change in bowel habits, anaemia, weight loss or a positive FIT, the doctor may recommend colonoscopy because the entire large bowel needs to be assessed.

The safest practical rule is: if bleeding occurs for the first time, returns, changes in character or causes concern, it is worth discussing it with a doctor. Treating presumed haemorrhoids with ointment without establishing the cause may delay appropriate diagnostics.

Symptoms that should not be ignored

More prompt consultation is particularly important in the case of:

• blood in the stool or rectal bleeding appearing for the first time,
• recurrent or worsening bleeding,
• dark, tarry stool,
• a positive FIT or faecal occult blood test,
• a change in bowel habits lasting more than a few weeks,
• new alternating diarrhoea and constipation,
• a feeling of incomplete evacuation or persistent urge to pass stool,
• unexplained anaemia or low iron levels,
• unintended weight loss,
• abdominal pain with loss of appetite, weakness or bloating,
• a family history of colorectal cancer or advanced polyps,
• inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease.

Severe abdominal pain, inability to pass gas or stool, vomiting, heavy bleeding, fainting or marked deterioration in general health require urgent medical help.

What is a colonoscopy?

Colonoscopy is an endoscopic examination of the large bowel. The doctor introduces a flexible camera through the anus to inspect the lining of the colon. During the examination, tissue samples can be collected for histopathological assessment, some polyps can be removed and the source of bleeding or other symptoms can be evaluated.

Colonoscopy is important not only because it helps detect cancer. It also allows polyps to be found and removed before some of them develop into malignant lesions. This is why colonoscopy may be both diagnostic and preventive.

The bowel must be cleansed before colonoscopy. Good preparation is important because retained bowel contents may make it more difficult to assess the mucosa and detect small lesions.

When should you undergo colonoscopy?

Colonoscopy is performed in two main situations: preventively in an asymptomatic person, or diagnostically when symptoms or abnormal test results are present.

Most importantly, a patient with symptoms is not a “screening patient”. Symptoms require diagnostics tailored to the situation, regardless of age and regardless of whether the patient formally qualifies for the preventive programme.

Colonoscopy screening programme in Poland — who can use it?

According to information from pacjent.gov.pl and the NFZ, the colorectal cancer screening programme is intended for asymptomatic people who have not undergone colonoscopy in the last 10 years and meet the age criteria.

The programme is available to:

• people aged 50–65,
• people aged 40–49 if a first-degree relative has been diagnosed with colorectal cancer,
• people who have not had a colonoscopy within the last 10 years,
• people without symptoms suggesting colorectal cancer.

If a patient has symptoms such as bleeding, anaemia, weight loss or a change in bowel habits, the screening programme should not be treated as the only pathway. Symptom-based diagnostics are then needed, often after a medical consultation.

Colorectal polyps — why are they important?

Colorectal polyps are protrusions of the bowel lining. Many are benign, but some — particularly adenomas and certain serrated lesions — may develop into cancer over time. This process usually takes years, which is why prevention is worthwhile.

Polyps often cause no symptoms. Sometimes they may cause blood or mucus in the stool, rectal bleeding, a change in bowel habits or anaemia. Colonoscopy allows them to be detected, removed and submitted for histopathological examination.

The histopathology result determines the follow-up plan. The doctor decides when the next colonoscopy should be performed based on the number and size of polyps, their microscopic structure and whether they were completely removed.

Anoscopy, rectoscopy or colonoscopy — how do they differ?

Patients often ask whether a proctologist will “see everything” during an office examination. The answer depends on what is being investigated. Different examinations assess different parts of the digestive tract.

A proctologist may therefore be the first doctor seen by a patient with rectal bleeding or anal pain. If symptoms suggest a problem higher in the bowel, the doctor may recommend colonoscopy or a gastroenterology consultation.

FIT and faecal occult blood — what does the result mean?

FIT detects blood in the stool that is not visible to the naked eye. A positive result does not automatically mean cancer because the blood may come from polyps, haemorrhoids, inflammation or other lesions. It is not, however, a result that should be ignored.

If FIT or a faecal occult blood test is positive, further diagnostics are usually needed, often colonoscopy. Repeating the test “to make sure” instead of proceeding with diagnostics may delay diagnosis.

A negative result also does not always end the matter if the patient has warning symptoms. FIT is a supporting tool but does not replace medical assessment in the case of bleeding, anaemia, weight loss or a persistent change in bowel habits.

Colorectal cancer in younger people — does age rule it out?

The risk of colorectal cancer increases with age, but younger age does not exclude the disease. A person in their 30s or 40s with bleeding, anaemia, a change in bowel habits, weight loss or a significant family history should not automatically be considered “too young for cancer”.

In younger patients, symptoms are more often attributed to haemorrhoids, stress, diet or irritable bowel syndrome. These causes are indeed common, but if symptoms are new, persistent, recurrent or accompanied by warning signs, diagnostics are needed.

Who should consider earlier diagnostics?

Some people have a higher risk of colorectal cancer and may require earlier or more frequent surveillance than the general population. This particularly concerns patients with:

• colorectal cancer in a first-degree relative, especially at a younger age,
• multiple polyps or advanced polyps in the past,
• inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease,
• genetic syndromes, such as Lynch syndrome or familial adenomatous polyposis,
• iron-deficiency anaemia without a clear cause,
• a positive FIT or positive faecal occult blood test,
• concerning bowel symptoms regardless of age.

In such situations, the timing and scope of diagnostics should be determined by a doctor. Screening programmes are important, but they do not cover every individual risk scenario.

Is colonoscopy painful?

Patients often fear the colonoscopy more than the result itself. The examination may be uncomfortable and may cause pressure, cramping or discomfort, but many centres offer colonoscopy under sedation or anaesthesia when indicated and when there are no contraindications.

For many people, the most difficult part is bowel preparation. It is nevertheless very important. The cleaner the bowel, the greater the chance that the doctor can inspect the lining carefully and detect even small lesions.

Fear of the examination is understandable, but it should not lead to postponing diagnostics for many months when warning symptoms or a positive screening test are present.

What does a colonoscopy result mean?

A colonoscopy may be normal or reveal various findings, such as haemorrhoids, diverticula, polyps, inflammation, bleeding, narrowing, a tumour or other abnormalities. If tissue samples were collected or polyps removed, histopathological examination is crucial.

Histopathology determines exactly what the removed or sampled lesion is. It may confirm a benign polyp, adenoma, serrated lesion, inflammation, dysplasia or cancer. Further recommendations depend on this result: observation, surveillance colonoscopy, endoscopic treatment, surgery or oncological treatment.

A patient should not be left alone with a colonoscopy or histopathology report. The result should be discussed with a doctor, especially if polyps were removed, biopsies were taken or another follow-up examination was recommended.

Common myths about colorectal cancer and colonoscopy

• “Blood definitely means haemorrhoids.” Not always. Haemorrhoids are common, but bleeding requires a diagnosis.
• “If it does not hurt, it cannot be cancer.” False. Colorectal cancer may remain painless for a long time.
• “Colonoscopy is only needed after the age of 60.” False. Screening has age criteria, but symptoms require diagnostics regardless of age.
• “A positive FIT means cancer.” False. It may have different causes but requires further diagnostics.
• “A negative FIT excludes cancer.” Not always, especially when warning symptoms are present.
• “A proctologist is enough to assess the entire bowel.” False. A proctologist assesses the anus and lower digestive tract, while colonoscopy assesses the whole large bowel.
• “Polyps are harmless if they do not hurt.” Many polyps do not hurt, but some have malignant potential.
• “Colonoscopy must always be painful.” False. Discomfort is possible, but different forms of sedation or anaesthesia may be available depending on the centre and eligibility.

Do you have rectal bleeding, a change in bowel habits or a positive FIT?

Do not immediately assume that it is haemorrhoids. A consultation helps determine whether proctological diagnostics are sufficient or whether colonoscopy is needed.

Diagnostics of colorectal symptoms at Wyspa Medycyny Przyjaznej in Gdańsk

At Wyspa Medycyny Przyjaznej, patients with rectal bleeding, pain, a lump, itching, burning, a feeling of incomplete evacuation or suspected haemorrhoids may begin diagnostics with a proctology consultation. The doctor assesses symptoms, performs a physical examination and, if needed, anoscopy.

If symptoms suggest that the problem may involve higher parts of the large bowel, the doctor may recommend further diagnostics, such as colonoscopy, laboratory tests, stool tests or a gastroenterology consultation. Proctology and gastroenterology often complement one another, particularly when the patient reports bleeding, a change in bowel habits or unclear intestinal symptoms.

Proctologist in Gdańsk Rectal bleeding Anoscopy versus colonoscopy

What should you ask the doctor if you are afraid of colorectal cancer?

• Could my symptoms come only from the anal area, or do they require assessment of the whole large bowel?
• Do I need anoscopy, rectoscopy, colonoscopy or a gastroenterology consultation?
• Does the blood look like fresh bleeding from the anal canal, or should a source higher in the bowel be investigated?
• Should I have a complete blood count, ferritin, iron tests or FIT?
• Does a positive FIT mean I need colonoscopy?
• Does my family history increase my risk of colorectal cancer?
• Do I qualify for the colonoscopy screening programme?
• How should I prepare for colonoscopy?
• Can the examination be performed under sedation or anaesthesia?
• What does the histopathological result of a polyp mean?
• When should colonoscopy be repeated after polyp removal?
• Which symptoms require urgent help?

FAQ — colorectal cancer, symptoms and colonoscopy

What are the first symptoms of colorectal cancer?

Colorectal cancer may remain asymptomatic for a long time. Possible signs include blood in the stool, rectal bleeding, a change in bowel habits, alternating diarrhoea and constipation, anaemia, weight loss, abdominal pain, mucus in the stool or a positive FIT.

Does rectal bleeding always mean cancer?

No. Common causes include haemorrhoids and an anal fissure, but bleeding should not automatically be attributed to haemorrhoids. New, recurrent or unexplained bleeding requires medical assessment.

When is colonoscopy needed?

Colonoscopy is performed preventively in people who meet screening programme criteria or diagnostically when symptoms such as bleeding, a positive FIT, anaemia, a change in bowel habits, weight loss or suspected polyps are present.

Who qualifies for the colonoscopy screening programme in Poland?

The programme is intended for asymptomatic people aged 50–65, or aged 40–49 if a first-degree relative had colorectal cancer, provided that the patient has not had a colonoscopy in the previous 10 years.

Can a young person develop colorectal cancer?

Yes, although the risk increases with age. Younger age does not exclude the disease when warning symptoms, a positive FIT, anaemia or a significant family history are present.

Can a proctologist replace colonoscopy?

Not always. A proctologist assesses the anus, anal canal and lower rectum, while colonoscopy assesses the whole large bowel. If symptoms suggest a problem higher in the bowel, colonoscopy may be needed.

Can anoscopy detect colorectal cancer?

Anoscopy assesses the anal canal and lower rectum. It does not examine the whole large bowel and therefore does not replace colonoscopy in colorectal cancer diagnostics.

Does a positive FIT mean cancer?

Not always. A positive FIT means that blood was detected in the stool. Possible causes include cancer, a polyp, inflammation, haemorrhoids or another condition. A positive result requires further diagnostics, usually colonoscopy.

Does a negative FIT exclude colorectal cancer?

Not in every situation. A negative result is reassuring, but a patient with warning symptoms such as bleeding, anaemia, weight loss or a change in bowel habits should still consult a doctor.

Are colorectal polyps dangerous?

Many polyps are benign, but some may develop into cancer over time. Detecting, removing and examining polyps histopathologically therefore has preventive value.

When is urgent medical help needed?

Urgent help is required for heavy bleeding, black tarry stool, severe abdominal pain, inability to pass gas or stool, vomiting, fainting, marked weakness or sudden deterioration in general health.

Sources for medical and editorial verification

• Pacjent.gov.pl, Colonoscopy — an examination that saves lives: https://pacjent.gov.pl/program-profilaktyczny/kolonoskopia-badanie-ktore-ratuje-zycie
• NFZ, Colorectal cancer screening programme: https://www.nfz.gov.pl/dla-pacjenta/programy-profilaktyczne/program-badan-przesiewowych-raka-jelita-grubego/
• Onkologia.org.pl, Malignant cancers in Poland: https://onkologia.org.pl/pl/epidemiologia/nowotwory-zlosliwe-w-polsce
• NHS, Bowel cancer screening: https://www.nhs.uk/tests-and-treatments/bowel-cancer-screening/
• NHS, Bowel polyps: https://www.nhs.uk/conditions/bowel-polyps/
• NHS England, Your guide to NHS bowel cancer screening: https://www.england.nhs.uk/long-read/your-guide-to-nhs-bowel-cancer-screening/
• American Cancer Society, Colorectal cancer screening recommendations: https://www.cancer.org/cancer/types/colon-rectal-cancer/detection-diagnosis-staging/acs-recommendations.html
• Wyspa Medycyny Przyjaznej, Rectal bleeding — causes and diagnostics: https://www.wyspamedycynyprzyjaznej.pl/pl/krwawienie-z-odbytu-wskazania
• Wyspa Medycyny Przyjaznej, Rectal bleeding: https://www.wyspamedycynyprzyjaznej.pl/pl/krwawienie-z-odbytu
• Wyspa Medycyny Przyjaznej, Anoscopy versus colonoscopy: https://www.wyspamedycynyprzyjaznej.pl/pl/anoskopia-vs-kolonoskopia
• Wyspa Medycyny Przyjaznej, Rectal polyps: https://www.wyspamedycynyprzyjaznej.pl/pl/polipy-odbytnicy-gdansk
• Wyspa Medycyny Przyjaznej, Proctologist in Gdańsk: https://www.wyspamedycynyprzyjaznej.pl/pl/proktolog-gdansk
• Google Search Central, Creating helpful, reliable, people-first content: https://developers.google.com/search/docs/fundamentals/creating-helpful-content
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