Blood in the stool: the most common causes

Every year, twenty percent of people discover blood in their stools. In most cases it is bright red blood, coming from a burst hemorrhoid or small cracks in the anus. You often see a few drops of blood on the toilet paper or on your stool. This is usually harmless. However, is there blood in your stool or is your stool black and sticky? Then there may be intestinal or stomach bleeding. This may have a more serious cause.
If you find blood in your stool, it is usually shocking. Although not all causes are serious, it is wise to go to the doctor. With a brief physical examination, he can quickly determine whether, for example, you suffer from relatively harmless hemorrhoids or a fissure. If the doctor suspects a more serious cause, he will refer you to the hospital for further examination.


Hemorrhoids are swollen blood vessels, a type of varicose veins. They are located at the end of the rectum and near the sphincter of the anus. If the blood vessels are very swollen, they can sometimes come out. The hemorrhoid is then visible and can be felt as a soft bump. A somewhat larger hemorrhoid can also give you the feeling that there is something constantly in your anus. Hemorrhoids can be painful, especially when you go to the toilet. If there is a lot of pressure on the hemorrhoid, it can rupture. You will then see a little bright red blood on the toilet paper, on or next to your stool or in your underwear. A hemorrhoid can also become infected or lead to irritation of the skin around the anus. Itching and a burning sensation are the result. A hemorrhoid occurs when you have to strain hard, for example with hard stools or during childbirth. Sitting a lot, insufficient exercise or being overweight increases the risk of hemorrhoids. A prolapsed hemorrhoid will no longer disappear. However, the complaints can be reduced by drinking plenty of water and eating a fiber-rich diet (bran, brown bread, whole wheat products). You keep your stool soft, so you don’t have to strain. It is also important not to postpone going to the toilet if you feel the urge. Your stool will then become thicker, which can make you more likely to suffer from constipation. Medicines (ointments, suppositories) are available for pain, burning and itching. Hemorrhoids are not dangerous. However, if serious complaints persist, medical intervention may be necessary.

Small cracks in the anus

If your stool is hard and you have to strain a lot, the skin of your anus may tear slightly. The crack (fissure) that then occurs is usually at the front or back of the anus. You will feel a sharp pain, especially during and after defecating. You may also lose some bright red blood through the tear. You will see this on the toilet paper or on or next to your stool. If your stool remains hard, the tear will burst due to the pressure – open again every time you visit the toilet. The sphincter of your anus can also become irritated and cramp. The blood no longer flows properly and the complaints become increasingly worse. When the doctor examines your anus, he will quickly be able to determine that you are suffering from a tear. The treatment is aimed at softening your stool: drink plenty of water, eat fiber-rich food and go to the toilet regularly. You can also use an ointment to promote healing. If complaints persist, minor surgery may be necessary.

Sexually transmitted disease

Sometimes bleeding from the anus is caused by a sexually transmitted disease. In most cases this concerns chlamydia: a bacterial infection of the mucous membrane. During anal sex, the bacteria settle in the mucous membrane of the anus. As a result, complaints such as itching, pain, a mucous discharge or blood loss from the anus may arise. The mucous membrane and the underlying blood vessels are then damaged in such a way that minor bleeding occurs. The blood is bright red and is usually not mixed with the stool. Chlamydia is easy to treat with antibiotics.

Chronic intestinal inflammation

Blood loss from the anus can also be caused by (severe) intestinal disorders. An important difference with the causes mentioned above is that the blood is not on or next to your stool, but is mixed with your stool. You often see clots or streaks of blood in your stool. Common causes include Ulcerative Colitis and Crohn’s disease. Both conditions fall under the heading of IBD, Inflammatory Bowel Disease or chronic intestinal inflammation.

Ulcerative colitis is a chronic inflammation of the large intestine, which usually starts in the rectum (just above the anus). Ulcers can develop in the mucous membrane of the large intestine, which often cause persistent diarrhea with mucus and blood. High fever, nausea, constipation and painful abdominal cramps are also common complaints. Over time, weight loss and anemia can develop. The symptoms are often worsened by stress. Ulcerative colitis is an autoimmune disease. Your body mistakes its own cells for foreign invaders and attacks them. Ulcerative colitis cannot be cured. The treatment consists of medications that should inhibit existing inflammation and prevent new inflammation. In addition, medications may be given against diarrhea and anemia. Sometimes it is necessary to surgically remove the inflamed part of the intestine or even the entire colon. Ulcerative colitis is a serious disease that can even be life-threatening if the inflammation is severe.

In Crohn’s disease, chronic inflammation usually occurs in the last part of the small intestine and the first part of the large intestine. However, the inflammation can occur in the mucous membrane of the entire digestive tract. Unlike ulcerative colitis, the ulcers in the intestinal mucosa in Crohn’s disease can penetrate quite deeply into the intestinal wall. Sometimes the ulcers heal on their own. However, the resulting scar tissue can lead to a narrowing of the intestine. If the ulcers do not heal on their own, they can sometimes grow right through the intestinal wall and also cause inflammation on the outside of the intestine. The inflammatory fluid then causes adhesion with other parts of the intestine, bladder, skin or vaginal wall. Crohn’s disease often causes severe abdominal pain, persistent diarrhea with (sometimes) blood and sores near the anus. The inflammation can also lead to fever and ultimately lead to severe fatigue and weight loss. The blood loss in the intestines sometimes causes anemia over time. The cause of Crohn’s disease is usually unknown. The disease cannot be cured either. The treatment consists of medications that should inhibit existing inflammation and prevent new inflammation. In addition, medications may be given against diarrhea and anemia. If the intestine is severely narrowed or even closed by scar tissue, surgery is necessary.

Very occasionally, a serious ‘normal’ intestinal infection also causes blood in the stool. Such an intestinal infection (gastroenteritis) is the result of micro-organisms (for example bacteria, a virus or parasites) that often enter your body through unhygienic food or contaminated drinking water. The complaints are often loss of appetite, nausea, (bloody) diarrhea, painful abdominal cramps and vomiting. In addition, general complaints may also arise, such as fever, painful muscles, extreme fatigue or lethargy. Antibiotics are only prescribed for a bacterial infection. Parasites are treated with other means. Your body must overcome a viral infection on its own.

A benign or malignant tumor in the large intestine

Benign (polyps) or malignant tumors can sometimes be the cause of blood in the stool. Just like with intestinal infections, the blood is mixed with your stool. Intestinal polyps are quite common. Colon cancer is much rarer.

A polyp in the colon / Source: Rsabbatini, Wikimedia Commons (CC BY-2.5)

polyp can develop in the mucous membrane of the large intestine ; a benign growth. A polyp is in principle a harmless proliferation of mucous membrane cells. However, in the large intestine, this proliferation can sometimes, over time, become malignant and lead to colon cancer. A colon polyp is therefore always surgically removed. The growth in the intestine can damage the mucous membrane and an underlying blood vessel and lead to bleeding. You will then see this blood in your stool. Stomach pain, difficulty going to the toilet, constantly feeling like you have to go to the toilet and weight loss can also occur. If the polyp narrows your intestine, it can lead to alternating constipation and diarrhea. A polyp in the colon can be diagnosed using an endoscopy (viewing examination), X-ray examination or a CT scan. After the polyp has been removed, you will always have to be monitored for a period of time.

Occasionally, colon cancer is the cause of blood in your stool. This form of cancer mainly occurs in people aged 60 and older and often arises from a polyp in the last part of the large intestine. You may then find blood, sometimes with mucus, in your stool. The further the tumor is from the anus, the darker the blood is. Your stool may even turn black. If the tumor is at the very beginning of the large intestine, the blood cannot always be seen with the naked eye. The tumor can partially block your intestine, causing alternating constipation and diarrhea. As a result, your stool sometimes also has the shape of a pencil. In addition, you may feel like you always have to go to the toilet, you may lose weight and have vague stomach pain or a painful spot in your abdomen. The loss of blood in the intestines can eventually lead to anemia, which can make you very tired and dizzy. The treatment of colon cancer depends on the location, size and nature of the tumor and any metastases and may consist of surgery, radiation and/or chemotherapy. The earlier colon cancer is diagnosed, the greater the chances of survival.

A stomach bleeding

Black, very sticky stools (tar stools) usually indicate stomach bleeding. Blood released so high in your body is converted into iron ions, which provide the black color. In most cases, stomach bleeding is the result of a stomach ulcer . This is an ulcer in the lining of the stomach or duodenum (the beginning of the small intestine). If the ulcer damages a blood vessel, stomach bleeding can occur. The condition is often caused by a bacterium (helicobacter pylori), but alcohol, smoking, certain painkillers and stress can also play a role. A stomach ulcer generally causes more symptoms than just black and sticky stools. A sharp, burning pain in your upper abdomen often occurs, especially during and after eating. If the ulcer is in your duodenum, you will have less discomfort after eating. The pain is most severe at night. Nausea and vomiting, heartburn and frequent belching are also common complaints. The pain and nausea usually make you eat less and lose weight quickly. With stomach bleeding, blood may also be visible in the vomit. A stomach ulcer can be detected with an endoscopy or X-ray examination. The treatment consists of medication (to eliminate the bacteria) and/or antacids in combination with dietary advice: no coffee, carbonated drinks, peppermint, spicy or fatty food, beans, peppers, onions and leeks. These products cause the production of more stomach acid or gases in the stomach.

Sometimes stomach bleeding is caused by a stomach polyp . This is a benign growth in the stomach wall. In rare cases, a polyp can develop into a malignant tumor over time. The polyp can cause inflammation of the stomach wall (gastritis), which can lead to upper abdominal pain, nausea, vomiting, bloating and loss of appetite. A (large) polyp can also cause bleeding in the stomach. The blood from the stomach then leaves your body when you vomit or go to the toilet. A stomach polyp is usually removed surgically. A malignant tumor in the stomach can cause the same symptoms as a stomach polyp, but is only very rarely the cause of rectal bleeding.


If blood is only present in your stool during menstruation, the cause may be endometriosis. The mucous membrane that lines the inside of the uterus sometimes extends to places outside the uterus. The mucous membrane is often located in the ovaries, but occasionally it also settles in the intestines. During menstruation, the mucous membrane of the uterine wall is shed and transported outside with the blood. The mucous membranes outside the uterus also respond to the hormonal cycle, which can cause them to bleed during menstruation. The endometrium in the intestines then causes monthly bleeding (blood in the stool). The mucosal cells in the ovaries or other organs cannot leave the body in the usual way. This can cause adhesions and blood cysts to develop in the ovaries. A lot of blood loss during menstruation, abdominal pain, lower back pain, constipation, diarrhea, pain during urination and pain during sex can also be the result. Endometriosis can be diagnosed with an ultrasound scan and must be treated because the condition, in addition to the pain it causes, can lead to infertility.

Very occasionally, anal bleeding is the result of certain medications , such as acetylsalicylic acid, NSAIDs (such as diclofenac, ibuprofen and naproxen) and some antidepressants (SSRIs). However, often the cause of anal bleeding is not found at all.

It is always important to go to the doctor if you find blood in your stool. The cause is usually harmless, especially when it concerns only a few drops of bright red blood on the toilet paper. Blood mixed in your stool or black, sticky stool are often signs of a more serious condition. Fast and good treatment is then necessary.

read more

    • Persistent abdominal complaints due to an intestinal polyp
    • Stomach polyps can sometimes cause serious complaints
    • Pain in the lower abdomen: uterus, fallopian tubes and ovaries
    • Anal fissure: painful, bleeding crack in the anus

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