Blood in Stool: 9 Common Causes & What to Do

The presence of blood in the stool is generally caused by an injury or damange at some point along the digestive tract, which starts at the mouth and ends at the anus. Blood may be noted in very scant amounts and may even go undetected, or it be present in copious amounts following a bowel movement. 

Usually, bleeding that occurs before the intestines (in the mouth, esophagus or stomach) will cause very dark, foul-smelling stool. This stool is known as melena, and it occurs due to blood digested in the stomach. Stool with bright red blood generally indicates bleeding in the intestines,  usually in the large intestine or anus. This stool is known as hematochezia. 

Depending on the type of bloody stool, the doctor can investigate for many underlying causes. They can be confirmed with testins like an endoscopy or colonoscopy, which will guide treatment. 

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The main causes of blood in stool are:

1. Gastroesophageal varices

Gastroesophageal varices are dilated vessels in the stomach or esophagus. They emerge due to changes in blood flow, and usually occur with illnesses like cirrhosis or cardiac failure. 

Varices that rupture lead to blood in the stool, which presents with a dark color and foul odor. This condition is also associated symptoms like weakness and vomiting blood. 

What to do: If you suspect you have gastroesophageal varices, you should consult a gastroenterologist for assessment and treatment. Treatment may involve the use of medications to decrease blood pressure, as well as changes to lifestyle habits and, in some cases, surgical repair. 

2. Gastric ulcers

A gastric ulcer is a small wound in the lining of the stomach. It causes abdominal pain and burning that worsens with meals. 

Sometimes, ulcers can bleed and cause symptoms like dark, foul-smelling stool, nausea, vomiting blood and worsening abdominal pain. Learn more about the symptoms of stomach ulcers and what can cause them.

What to do: It is important to identify the cause of the ulcer so that the most appropriate treatment can be initiated. The doctor may order testing, like an endoscopy and an H. pylori test. Symptoms can be managed by reducing stomach acid production with medications like antacids and omeprazole.

3. Esophagitis

Esophagitis is inflammation of the esophagus can can cause symptoms like heartburn (particularly after meals), pain with swallowing and acid reflux. If left untreated, esophagitis can lead to bleeding, which can be noted as dark stool with an intense odor. Stool may also contain bright red blood. 

What to do: You should consult a gastroenterologist, who may prescribe medications to inhibit stomach acid production, like omeprazole and antacids. The doctor may also suggest some changes to diet. 

4. Hemorrhoids and anal fissures 

Hemorrhoids and anal fissures can lead to bright red blood in the stool. These conditions are usually related to constipation, as dry and hardened stool requires increased straining to eliminate them. Check out the causes of hemorrhoids and the other symptoms they can present with. 

What to do: To prevent new hemorrhoids and/or anal fissures, it is important to increase your fiber and water intake. These measures promote softer stool and consistent intestinal flow. Pain can be relieved with medicated ointments that contain anesthetic and healing properties. Sitz baths are another great way to naturally manage discomfort from hemorrhoids. 

5. Diverticuli

Diverticuli are small changes in the wall of the large intestine that occur due to excessive straining with bowel movements. Usually, diverticuli do not cause any symptoms, but they can lead to blood vessel injury in the areas where they appear. Damage to blood vessels usually occurs with hardened stool and can lead to bleeding. 

What to do: It is important to consult a gastroenterologist to indicate the most appropriate treatment for diverticuli. They are usually managed with changes to diet and increased fiber and water intake. 

6. Crohn’s disease

Crohn’s disease is a chronic inflammation of the intestinal lining that causes symptoms like abdominal pain, fatigue, weight loss, diarrhea and bloody stools. Read more about what causes Chrohn’s disease and other symptoms it can present with. 

What to do: If you suspect you have Crohn’s disease, you should consult a gastroenterologist for assessment. The doctor will usually order stool testing and a colonoscopy to confirm a diagnosis. This condition is typically managed with diet changes and medications like immunomodulators. 

7. Intestinal polyps

Intestinal polyps normally do not cause any symptoms, however larger polyps can lead to abdominal pain, diarrhea or constipation, and the presence of blood in the stool. 

What to do: Intestinal polyps that are identified during a colonoscopy are usually removed during the procedure.  

8. Medication use

The main medications that can cause bloody stools are anti-inflammatories (like diclofenac or ibuprofen) and platelet aggregation inhibitors (like aspirin or clopidogrel). However, other medications that interfere with blood coagulation, like warfarin, heparin and rivaroxaban, can also increase this risk.

What to do: It is important to take medications only as directed by your doctor. If there is an increased risk for bleeding due to medication use, omeprazole can be prescribed to further protect the stomach lining (as even small wounds are prone to bleed with certain medications). 

Bloody stools caused by medications should be reported to the prescribing doctor, who may discontinue the medication or consider an alternative. If the bleeding is intense and causes symptoms like low blood pressure or drowsiness, it is important to seek urgent medical attention. 

9. Intestinal or stomach cancer

Bloody stools are a common symptom of intestinal or stomach cancer, and can be accompanied by other symptoms like loss of appetite, abdominal pain, excessive fatigue and weight loss for no apparent reason. 

What to do: It is important to consult a gastroenterologist and to complete testing to confirm the type and stage of cancer present. These characteristics will help to identify the best treatment approach, which may involve chemotherapy, radiation therapy and/or surgery. 

When to go to the hospital

It is important to seek immediate medical attention if you experience bloody stools with the following symptoms: 

  • Drowsiness
  • Paleness 
  • Weakness
  • Low blood pressure
  • Vomiting with blood
  • Persistent blood in stools 

In these cases, bleeding may be serious and requires urgent assessment to identify the source of bleeding and stop it. Usually, the doctor will order an endoscopy or colonoscopy, and further surgery to repair damaged vessels may be necessary. Medications like omeprazole and octreotide may be prescribed depending on the underlying cause.