Finding blood in your stool can be a scary experience. While many causes of blood in stool are minor and require little to no treatment, blood in the stool can sometimes signify a serious problem. This blog will help you understand the difference between visible and occult blood in stool, the types of tests that can identify occult blood in stool, common causes of bleeding, and when to see a doctor.
Types of Blood in Stool
Blood in the stool is generally broken down into two categories — visible and occult. Visible blood can be seen in your stool, in the toilet, or on toilet paper after having a bowel movement. Occult blood isn't visible to the naked eye. It can only be detected with testing.
Visible Blood
Visible blood in stool ranges in color and appearance. It can be bright red or dark red. It can also be very dark or black and give your stool a tar-like appearance. The color of the blood can help point to where in your digestive tract it's originating from.
Visible blood can be caused by something as minor as hemorrhoids or as serious as colorectal cancer. It's important to track any bleeding you experience and report it to your doctor [1].
Occult Blood
If you have a small amount of blood in your stool, you may not be able to see it. Blood that can't be seen, known as occult blood, can only be detected through testing. If your doctor suspects occult bleeding or wants to test as a precaution, they can order a lab test. There are two types of tests your doctor might order:
- Guaiac-based fecal occult blood test: You place a stool sample on a small card that is coated with a chemical called guaiac and send it to a lab or your healthcare provider. When there is blood in the stool sample, the card changes color due to the interaction of blood with guaiac.
- Fecal immunochemical test: You put a small stool sample on a card or in a tube and send it to a medical lab — the lab tests for blood in the stool sample using an antibody that binds to hemoglobin.
Before taking a guaiac-based test, your doctor may tell you to avoid certain medications, supplements, and foods because they could cause false positive or false negative results. Before a fecal immunochemical test, you may also need to avoid taking certain medications, such as blood thinners, but you won't generally be required to make any dietary changes [2].
You can also test for blood in your stool at home without a doctor's order. To test your stool yourself, you'll need to purchase an over-the-counter fecal occult blood test kit. Some over-the-counter test kits show you your results in minutes. Others require that you send your stool sample to a lab for testing.
When to Test for Occult Blood in Stool
Your doctor may test for occult blood in your stool for a number of reasons, including [1], [3]:
- Anemia (low red blood cell count)
- Iron deficiency
- Abdominal or rectal pain
- Fatigue
- Weight loss
- Changes in bowel movements
- Black stool
Testing for occult blood in your stool is also a screening method for colorectal cancer. Even if you have no symptoms, the Centers for Disease Control and Prevention (CDC) recommend that you start screening for colorectal cancer at age 45 [4]. Your doctor may recommend that you begin testing even earlier if they determine that you are at high risk [5].
Causes of Blood in Stool
There are many possible causes of blood in stool, ranging from minor to life-threatening [1] [5]. Some of the common causes include:
- Hemorrhoids: Swollen veins in the anus or lower rectum
- Anal fissure: Tear or split in the anus
- Rectal prolapse: Rectum that has descended through the anus
- Diverticulitis or diverticulosis: Pouches in the lining of the digestive tract that may become inflamed or tear
- Rectal polyps: Growths in the lining of the large intestine
- Inflammatory bowel disease (IBD): Used in reference to Chron's disease or ulcerative colitis. IBD is categorized as chronic inflammation in the digestive tract
- Ulcers: Open sores in the stomach or upper small intestine
- Colorectal cancer: Cancer in the colon or rectum, which often starts as a polyp
When to See a Doctor
Finding blood in urine or stool is always something you should bring up with your healthcare provider. Blood in stool is sometimes benign, but it's difficult to determine the cause yourself, and some causes need prompt treatment. Even when the cause of bleeding appears to be obvious, something more serious could be going on. For example, hemorrhoids are a benign cause of bleeding that you can often treat easily at home. But rectal prolapse, which usually needs to be treated surgically, can be mistaken for hemorrhoids.
Be sure to keep a record of the bleeding, so you can inform your doctor of when it occurred and what it looked like. Even intermittent bleeding should be checked out. Your doctor may be able to determine the cause of bleeding based on your symptoms and a physical examination. Or they may order more testing to identify what's causing blood in your stool.
Accompanying Symptoms
There are some symptoms that can accompany blood in stool that indicate a serious problem. Get medical help immediately if you experience blood in your stool along with any of the following symptoms [2]:
- Chest pain
- Shortness of breath
- Lightheadedness
- Abdominal pain
- Yellowing of skin or eyes
- Nausea and vomiting
- Fever
- Difficulty swallowing
Summary
You should always inform your healthcare provider if you experience visible or occult blood in your stool. There are many causes of blood in stool, and some require medical intervention. Bleeding can also be the first indication of a more serious problem. If you or your doctor suspect that you might have occult blood in your stool, you can test a sample of your stool at home or send it to a lab for further testing. Fecal occult blood tests can also be used as a tool to screen for colorectal cancer.
