Blood On The Outside Of The Stool: 7 Causes & When To Worry.

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 Blood on the outside of the stool is usually caused by diseases affecting the last part of the colon, the rectum, and the anal canal. The most common causes are hemorrhoids, anal fissures, rectal polyps, and anal or rectal cancer.

In this article, You will learn about the common causes of blood on the outside of the stool, their symptoms, and when to worry.


Table of Contents

Why Blood appears on the “outside” of the stool (and not mixed with it)?

You may get scared when you see red blood outside your stool. Fortunately, the majority of cases are benign.

But Before we dive into the cause, I will explain why the blood sometimes appears on the “outside” of the stool.

Your stool gradually acquires its semi-hard form as it passes through your colon. How blood is mixed with your stool depends on the site of the bleeding source.

  • Bleeding sources early in the colon or all intestines: usually result in the complete mixing of blood with stool (which may also turn blackish).
  • Bleeding from the last part of the colon: Anal canal, rectum, and sigmoid colon bleeding can lead to blood on the outside of the colon.

In other words, blood joining stools appear on the outside of the stool after being formed. And this usually happens if the bleeding site is in the last part of your colon (particularly the rectum and anal canal)


Why shouldn’t you Panic?

The good news is the majority of causes of blood on the outside of your stool are usually benign.

Minimal Bright red blood per rectum occurs in about 15% of adults (3 of every 20 people) (ref). So, it is a common condition even in younger adults.

In most cases, piles (hemorrhoids) or piles. Those two causes represent up to 95% of causes.

Other serious causes are very rare and usually have warning signs.

However, You must have a diagnosis from your doctor. Don’t ignore any form of bleeding per rectum, especially if you are older than 40.

Common causes of blood on the outside of the stool:

(1) Piles (hemorrhoids):

Piles or hemorrhoids present are the most common cause of blood on the outside of your stool. According to current statistics, it is present in up to 95% of people.

Piles are common in people with chronic constipation. Either with constipation-predominant IBS or Chronic Idiopathic Constipation.

Hemorrhoids are dilated and enlarged blood vessels in the wall of your anorectal region.

Constipation is not the only cause of hemorrhoids, an

Sings and symptoms suggesting hemorrhoids:

  • Painless bleeding: usually, the blood you see on the outside of the stool or the toilet paper is not associated with pain (unless inflamed hemorrhoids).
  • With Inflamed Hemorrhoids: bleeding can be painful and associated with some itching around the anus.
  • A skin tag may be present at the opening of the anal canal (with external hemorrhoids).

How to manage bleeding from hemorrhoids:

  • First, it is important to get the diagnosis confirmed by your doctor.
  • Colon cancer is sometimes diagnosed in people who have ignored bleeding for years as they assumed it was from piles.
  • Avoid constipation using laxatives, stool softeners, and a high-fiber diet.
  • Ask your doctor about the proper medication and the need for surgery.

blood in stool with IBS

(2) Anal Fissure:

Another common cause of blood on the outside of your stool is anal fissures. An anal fissure usually causes pain during defecation.

It is usually caused by trauma to the anal tissue, commonly due to the passage of hard stool (constipation), and during normal vaginal delivery in females.

Symptoms and signs suggesting anal fissure:

  • History of chronic constipation or any trauma to the anal canal.
  • Pain is usually very severe and unbearable during defecation and mild or absent in between bowel motions.
  • The color is bright red, usually on the outside of the stool.
  • In severe cases, it may cause lower back pain.

What to do if you suspect an anal fissure:

  • First, consult your doctor to confirm the diagnosis and treat the cause.
  • Usually, the characteristic history is sufficient for the doctor, but it may ask you for a “digital Rectal Examination” to confirm the diagnosis.
  • Prevent hard stool by taking laxatives, stool softeners, and high-fiber foods.
  • Ask your doctor about the best medications (local gel or cream plus pain pills) if the condition is severe.

Uncommon causes of blood on the outside of stool:

(1) sigmoid or rectal polyp

Colon polyps are very common (about 30% of Americans will have them at 50).

A polyp is a finger-like or cone-like growth inside your colon’s inner wall. A polyp growing in the last part of your colon (sigmoid and rectum) may ulcerate and cause blood outside the stool.

There are two types of polyps:

  • Inflammatory polyps (low tendency to turn malignant): it is also called “hyperplastic polyp” and can be a source of bleeding on the outside of your stool.
  • Adenomatous Polyp (Relatively higher risk of turning malignant): especially if it is larger.

Symptoms suggesting colon polyps:

  • No symptoms: usually, most colon polyps persist for years without any symptoms. And occasionally discovered when it causes bleeding. Also, many of them are discovered accidentally during colonoscopy.
  • Bleeding: This can range from streaks of blood on the outside of the stool to frank bleeding per rectum.
  • Pain: but it is uncommon.

NOTE: because of the asymptomatic nature and the potential for malignancy, you should start testing for these polyps at 45-50. This is because the incidence of colon polyps increases with age.

(2) Rectal ulcer.

A rectal ulcer is a painful sore inside the rectum. It can be caused by:

  • Constipation and straining.
  • IBD (chrons or Ulcerative Colitis).
  • Solitary Rectal Ulcer Syndrome (unknown cause).

Signs and symptoms suggesting rectal ulcer:

  • The ulcer may occasionally bleed (especially with constipation), leading to blood on the outside of the stool.
  • Pain in the rectum (which may radiate to the lower back).
  • Painful bowel movements (similar to symptoms of anal fissures).
  • A sense of incomplete evacuation of your rectum

It is difficult to tell the difference between some anorectal ulcers and anal fissures. Always check for the cause with your healthcare provider.

(3) Rectal inflammation (Proctitis).

Your rectal lining can get inflamed alone (Proctitis) or with sigmoid colon inflammation (Recto-sigmoiditis).

The main causes of Proctitis:

  • Sexually transmitted diseases (Gonorrhea, Genital Herpes, Chlamydia infection).
  • Other infections: Such as Bacillary dysentery, Salmonella, and Campylobacter infection).
  • Inflammatory Bowel Disease (IBD).
  • Some medications (especially antibiotics).
  • Rectal Radiotherapy & others, Learn more HERE.

Signs and symptoms suggesting Proctitis:

  • Dysentery: usually, you experience dysentery or dysentery-like symptoms, where the stool becomes looser.
  • And is associated with blood, mucous, or both.
  • Lower abdominal pain with or without fever.
  • A Known history of IBD, or STD.

(4) Rectal or anal cancer.

In the USA, Colorectal cancer is the second cause of death in men (and the third in women).

However, it is a relatively rare cause of blood on the outside of stool compared to piles and anal fissures).

Only anorectal cancer can cause blood on the outside of stools. Classical colon cancer usually results in red or blackish blood MIXED with stools.

How to suspect recall or anal cancers:

  • Anal or rectal Pain: continuous dull Pain.
  • A sense of Lump in the inside of the rectum.
  • Bright red blood comes separately or on the outside of the stool.
  • Unexplained Anemia, Weight loss, fever.
  • Being older (more than 45 or 50 years old).

Any Blood with a stool in ages over 45 years should be carefully investigated. Ask your doctor about the probable investigation you need.

How will your doctor investigate the cause?

Your doctor will perform several tests to investigate the cause of the blood outside the stool. The main tests are:

Physical examination:

Your doctor may perform a rectal examination by:

  • First, inspect the outside of the anus.
  • Insert a gloved finger into the rectum to feel for lumps or abnormalities.
  • Anoscopy: a rigid tube is inserted to visualize the anal canal (performed in the doctor’s office and doesn’t require sedation).


A flexible tube is inserted to examine the lower part of the colon (the anal canal, the rectum, and sigmoid colon).

The advantage of sigmoidoscopy is being less painful and doesn’t require intensive preparation or sedation. But it cannot visualize the entire colon.


Colonoscopy is just like a sigmoidoscopy, but it has the advantage of screening the entire colon.

Other tests:

Your doctor may require additional investigations such as stool analysis, complete blood picture, abdominal Computed Tomography (CT), or STD testing.

When to see your doctor?

If your experience blood on the outside of the stool, you should see your doctor when:

  • Unknown or undiagnosed cause of bleeding into the stool.
  • Large amounts of bleeding in the stool.
  • Change in frequency or consistency of your bowel movements.
  • Abnormal abdominal pain.
  • Feeling very tired.
  • Unexplained anemia, weight loss, or fever.

MORE: Can Stress Cause Bloody stools? & when to worry?