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Blood in the stool

Written by Caidr's team of doctors and pharmacists based in UK | Updated: 22.02.2023 | 3 min read

Blood in the stool, or rectal bleeding, is where blood is found coming from the rectum. You may notice this mixed in with the stool or after passing stool, either on the tissue or in the toilet. It’s important to seek medical attention, as this indicates that some part of the gut is bleeding.

The stool may be different colors. If it is bright red, it usually indicates a bleed towards the end of the intestine, either from the colon or rectum. Darker red stool indicates that there may be bleeding higher up in the gut, in the lower small intestine. Black, tarry schools indicate bleeding from much higher up, from the stomach or upper small intestine.

What are the causes of rectal bleeding?

Bright red blood can be caused by hemorrhoids, or a tear in the anus called an anal fissure. These are most often caused by straining from constipation. If you are on medications that thin the blood, like warfarin or aspirin, this can increase your likelihood of bleeding.

Anal sex can cause trauma that leads to bleeding from the rectum, and sexually transmitted infections from anal sex may also be responsible.

Blood mixed in with the stool is caused by issues higher up in the gut. Examples include inflammatory bowel diseases like ulcerative colitis or Crohn’s disease, stomach bugs or anal fistulas.

Blood mixed in with stool can also be a worrying sign of bowel cancer, which is common but more likely in those with a history or family history of colon polyps or those older than 65 years old.

Dark stools can look black and can be caused by certain foods or medications like iron tablets. Eating beetroot can cause stool to look red, purple, or a dark blackish color.

Dark black stool has more worrying causes, such as stomach or small intestine bleeding from a stomach ulcer, diverticulitis, or blood-thinning medications like warfarin.

When should I see my doctor?

If you experience bleeding from the rectum and you can’t identify a cause, such as hemorrhoids that you feel confident treating at home, you should book an appointment with your doctor.

They will ask about your symptoms and family history, about certain lifestyle factors like smoking, alcohol intake and diet, and they will examine your abdomen. With your permission, they will also likely do a rectal exam.

Blood tests will be important to look for signs of anemia or infection. Stool samples can be sent off to look for blood in the stool and can help identify any infections that may be present, or to look for evidence of any inflammation. Further investigations may be required such as procedures like colonoscopy or imaging such as a CT scan.

When should I seek a doctor urgently?

Rectal bleeding may be associated with rectal pain or abdominal pain, or cramping.

Urgent medical advice is required for significant loss of blood that leads to dizziness, tiredness, rapid breathing, confusion, or fainting.

Additionally, if the rectal bleeding doesn’t stop, if there is severe anal pain, or if you are also vomiting blood, then you should seek urgent medical attention.

If your symptoms are not improving on their own or with medication from your pharmacy, you should contact your doctor for further review.

How can rectal bleeding be treated?

Treatment very much depends on the cause. Hemorrhoids can be treated by over-the-counter remedies. Constipation can be prevented by exercising regularly, drinking plenty of fluids, and eating high-fiber foods.

Cancer of the bowel requires specialist treatment and may need a combination of surgery, chemotherapy, and radiotherapy to help manage the disease.

Inflammatory bowel disease requires medication and regular reviews by a specialist team.

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