The cause may not be serious, but you should still get checked out by a doctor.

One of the most concerning symptoms you can experience is suddenly having blood in your stool. It can be scary to see bright red when you’re not expecting it — and it can bring up fears of cancer.

Although that is one possible cause, the likelihood is the bleeding is from another, less concerning source. It could also be that something you’ve eaten, such as beets, tomatoes or foods with red dye, is giving the false appearance of blood.

But you should never dismiss blood in your stool, according to Kyle G. Cologne, MD, an assistant professor of colorectal surgery at the Keck School of Medicine of USC and a colon and rectal surgeon at Keck Medicine of USC.

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“Bleeding is not normal,” Dr. Cologne said. “While there are many benign causes, such as hemorrhoids, fissure, diverticulitis and colon polyps, this may be a sign of another problem that requires more specialized treatment, like colorectal cancer or inflammatory bowel disease.”

Causes of blood in stool include:

An ulcer

You might not realize that blood can travel all the way from your upper GI tract. If the blood appears black or very dark, that’s probably where it’s coming from, and it may indicate an ulcer.

Hemorrhoids and fissures

Bright red blood usually originates from the lower colon, rectum or anus, and is a common sign of hemorrhoids or fissures. Hemorrhoids are a swelling of veins that can occur from straining, and fissures are small tears that can happen after passing a hard stool.

Diverticulitis

Diverticulitis starts when small pouches in the intestines form. Although these pouches are benign on their own, they can lead to complications, such as an infection called diverticulitis that can cause bleeding.

Inflammatory bowel disease

IBD, which includes colitis and Crohn’s disease, is an inflammation of the intestines, which can cause bleeding. You might have other symptoms, such as abdominal pain or diarrhea, as well.

Colon cancer

Blood signaling cancer might not be noticeable to the eye, so be sure to follow your doctor’s recommendations for regular colonoscopy screenings based on your personal and family history. Polyps, which may or may not be precancerous, may bleed, and they can be located and removed during colonoscopies.

Your doctor might perform certain tests, including a colonoscopy, an endoscopy, X-rays or CT scans, to locate the source of the bleeding. Other symptoms you may have, such as pain, vomiting, weakness, weight loss or stool changes, can help diagnose you as well. Treatment will depend on the underlying cause of the blood and may include medications, topical treatments, surgery or diet changes.

The best way you can prevent blood in stool is a high-fiber diet that can keep you regular without straining. Because hemorrhoids and fissures are common causes of bleeding, taking care to avoid them can reduce the likelihood you’ll see red. Plus, keeping regular can help your overall digestive health.

Even if you think the cause of the blood is from a benign source such as a hemorrhoid, you should still consult your doctor just in case. “If detected and treated early, this results in much better outcomes,” Dr. Cologne said. “So don’t delay in seeking care to evaluate bleeding.”

By Tina Donvito

If you have blood in your stool, make an appointment with one of our colorectal specialists at Keck Medicine of USC. If you are in the Los Angeles area, schedule an appointment by calling (800) USC-CARE (800-872-2273) or by visiting keckmedicine.org/request-an-appointment.