Crohn's and colitis, blood in the stool and bowel screening

What questions are behind this page?

“Is this blood from haemorrhoids or something worse?”, “My diarrhoea and cramps have gone on for months without going away, could it be colitis?”, “My father had bowel cancer, what should I do?”, and “What does screening mean?”. This page answers these. What matters: most blood that people see has a simple cause, but you should not diagnose any of it yourself.

Inflammatory bowel disease (Crohn’s disease and ulcerative colitis)

NIDDK describes Crohn’s disease as a long-term condition in which a faulty immune response causes inflammation in the digestive tract. It can affect anywhere from the mouth to the anus, but usually the small bowel and the start of the large bowel. Ulcerative colitis, according to NHS, is inflammation of parts of the large bowel and the rectum. Both belong to the group of inflammatory bowel diseases.

Cause. NHS says the exact cause is not known and the immune system seems to attack healthy tissue. Genetics plays a part. Family history and smoking (for Crohn’s) are risk factors. NIDDK says Crohn’s can occur at any age and in any ethnic group but is seen most often at around ages 20 to 29, or in people with a relative who has it (usually a sibling or parent) and in smokers. NHS also says it most often starts in teenagers and young adults, but it can happen at any age.

Symptoms (Crohn’s, NHS). Diarrhoea, blood or mucus in the stool, abdominal pain, constipation, anal pain, tiredness, loss of appetite and weight loss. Symptoms come in phases: a flare-up (which can last from days to months) and a period of remission. Joint pain, red eyes and skin rashes may also occur. In children, slow growth or delayed puberty can be a sign.

Symptoms (ulcerative colitis, NHS). Loose stool with blood, mucus or pus, pain in the lower left abdomen that often eases after a bowel movement, a sudden, frequent or night-time need to use the toilet, a feeling of needing to go even when the bowel is empty, anal bleeding, bloating. Less often: constipation, tiredness, loss of appetite and weight loss. During flare-ups there may also be fever, joint pain and mouth ulcers.

Assessment. NHS says it often starts with blood and stool tests, and then, to confirm, an endoscopy (colonoscopy or gastroscopy), biopsy and imaging (MRI, CT or ultrasound) may be needed. No single test confirms Crohn’s disease, and it may take time. Which of these you need is your doctor’s decision. If a colonoscopy is needed, read the preparation guide, but the instructions of the centre doing it come first.

Treatment. NHS lists the treatment groups like this: anti-inflammatory medicines, medicines that regulate the immune system, biological treatments, medicines to relieve symptoms, and sometimes (for children or people who cannot take steroids) liquid nutrition, and in some cases surgery (removing the damaged section or creating a stoma) if medicines do not work. Do not start or stop any of them yourself. The type of medicine, the duration and the follow-up are decided by the specialist and may change over time. About Crohn’s, NHS says there is currently no cure and the condition is long-term, and about colitis it says treatment can calm symptoms and reduce the chance of relapse.

Pregnancy and having children. NHS says a healthy pregnancy is usually possible, but you should talk to a specialist before deciding, because not all medicines are suitable in pregnancy and some affect male fertility.

Long-term follow-up. NHS says both conditions raise the risk of bowel cancer and people at higher risk may have regular colonoscopies. This does not mean cancer is certain; it means follow-up is needed. NHS says Crohn’s may also affect the joints, bones, skin, eyes, kidneys and liver and cause vitamin deficiency, and colitis may lead to anaemia and weaker bones. For this reason tiredness or joint pain should also be mentioned to the doctor.

If you need nutrition or psychological counselling, the patient support section introduces the related services.

Blood in the stool

NHS groups the causes of blood by its colour and type:

• Bright red blood on toilet paper, streaks, or red water in the toilet: haemorrhoids, anal fissure (a small tear in the anus, often after constipation), sexually transmitted infections or injury, blood-thinning medicines or aspirin, and broken blood vessels in the bowel.
• Blood in the stool or blood mixed with mucus: anal fistula, gastroenteritis, inflammatory bowel disease, polyps or early bowel cancer.
• Very dark or black stool: iron tablets or dark food, or bleeding in the stomach or bowel from injury, blood-thinning medicine or aspirin, or a stomach ulcer.

NHS says “do not diagnose it yourself” and to see a doctor if you are worried. If you take a blood-thinning medicine or aspirin, do not stop it yourself and tell your doctor.

NHS gives these as non-urgent reasons to see a doctor: blood in a child’s stool, blood in the stool for three weeks, stool that is looser, thinner or longer than usual for three weeks, severe pain around the anus, pain or a lump in the abdomen, more tiredness than usual, unexplained weight loss. Three weeks is an upper limit, not a waiting time: show repeated bleeding sooner.

The doctor may examine the anus and rectum with a gloved finger (NHS), ask for a stool sample, or refer you to a specialist. If this examination worries you, ask beforehand what they will do and why.

Screening is different from “checking symptoms”

Screening means testing a person who has no symptoms, to find a dangerous change before it causes symptoms. WHO says regular screening, wherever an organised programme exists, is the most effective way of finding cancer early and preventing it (by finding and removing precancerous lesions), and it has been shown to reduce both incidence and deaths. In its 2021 guideline abstract, ACG says the aim of screening is to remove adenomas and serrated lesions and to detect cancer at an early stage.

Checking symptoms means a person who has seen blood, or has new diarrhoea or constipation, or weight loss; this is not screening and should not be put off until a screening appointment.

Who and from what age? Here the guidelines do not agree exactly, and it depends on the person’s risk. In 2021 USPSTF recommends screening for all adults aged 50 to 75 with high certainty and for those aged 45 to 49 with moderate certainty; this applies to people with no symptoms and average risk (no history of bowel cancer, adenomatous polyps or inflammatory bowel disease, and no personal or family history of a high-risk genetic condition such as Lynch syndrome). The UK NHS national programme sends a home sample every two years from age 50 to 74. WHO does not give a number for the screening age. So the starting age for you is set by your doctor, taking into account family history, history of polyps or bowel disease, and symptoms. WHO says people with a family history or hereditary syndromes may need genetic counselling and tailored screening.

Which tests? NHS describes the FIT test, which is done at home with a small stool sample, finds tiny amounts of blood, and if blood is found, a colonoscopy usually follows. NHS says blood often has a lower-risk cause such as a fissure or a polyp. A negative result does not completely rule out cancer, and if you develop symptoms you should see a doctor. Colonoscopy is another method your doctor may suggest. The suitable option is chosen according to your age, risk, access and preference. Ask your doctor or health centre about Iran’s screening programme.

What lowers the risk? WHO lists a diet rich in fruit and vegetables, avoiding smoking, physical activity, a healthy weight and limiting alcohol, and says a lot of processed and red meat, inactivity, obesity, smoking and alcohol are linked with higher risk.

Worried about “cancer”?

Fear is natural, and taking it seriously is part of care. WHO writes that bowel cancer is the third most common cancer in the world and in the early stages often has no symptoms or mild ones. The symptoms WHO lists: a change in bowel habit, blood in the stool (bright red or dark and tarry), persistent abdominal cramps or pain, sudden weight loss, persistent tiredness and anaemia. WHO says survival depends greatly on the stage at diagnosis, and in some high-income countries incidence and deaths have fallen because of earlier diagnosis. But none of this means your symptoms are cancer. It means that finding it early is worthwhile.

When to act urgently

Call 115 (Iran’s emergency number) right now (NHS): anal bleeding that does not stop, or a lot of blood and a large clot when passing stool, severe abdominal pain, vomiting blood or what looks like coffee grounds, or being completely unable to pass stool or wind with abdominal pain.

See a doctor or go to the emergency department the same day (NHS): black or dark red stool, bloody diarrhoea, fever or chills, or a fast heartbeat.

Book an appointment soon: blood in the stool that keeps coming back, a change in bowel habit that has lasted three weeks, unexplained weight loss, tiredness and paleness, or if you have a family history of bowel cancer and want to ask about screening.

See the full list in urgent signs.

This page is for information and does not replace an examination.