7 Causes of Blood in Stool with IBS & When to Worry

Our content is not intended nor recommended as a substitute for medical advice by your doctor. Use for informational purposes only.

IBS is not associated with blood in stools. Usually, blood in stool is due to other conditions that coexist with IBS.

Some of these conditions (like anal fissure) may be due to severe IBS-constipation. However, the majority of cases are not a result of IBS.

Today, I will explain to you the most common causes of bloody stool with IBS, how to know them, and when you need to consult your doctor.

The possible causes of blood in stool with IBS are:

  • Anorectal fissure associated with IBS-Constipation.
  • Piles (hemorrhoids).
  • Colon Polyps.
  • An attack of dysentery.
  • Bleeding tendency.
  • Angiodysplasia (fragile blood vessels).
  • Inflammatory Bowel Diseases “IBD”: (Crohn’s disease or Ulcerative Colitis).
  • Colon cancer.
  • Diverticular disease.
  • Upper GIT bleeding (bleeding from the duodenum, stomach, or esophagus).

Table of Contents

(1) Anal Fissure Associated With IBS-Constipation.

An anorectal fissure is a breakdown in the lining mucosa of the anal canal. The most common cause of anorectal fissure is chronic constipation.

People with IBS-C may develop anorectal fissures from hard stools and straining.

How To Know That Bloody Stool Is Due To Anorectal Fissure:

  • If you have severe constipation-predominant IBS.
  • If you experience severe pain during the defection.
  • Usually, the pain is mild or not present between defecations.
  • The amount of blood is minimal, mixed with the hard stool. Usually bright red.

As constipation leads to anorectal fissures, Also anorectal fissure leads to more constipation. This “vicious circle” can worsen your IBS. 

What To Do If You Think You Have Anorectal Fissure:

  • The first thing you should do is consult your doctor about this condition. Your doctor will ask you some questions about your symptoms.
  • Usually, the doctor will ask you to visually inspect the perineal area and may need a “digital rectal examination” to confirm the condition.
  • You should prevent constipation by eating more fiber (gradually) and taking laxatives to improve this condition.
  • Your doctor may prescribe medications ( mostly local cream or gel) to decrease the pain and relax the spasm in your sphincter.
  •  You don’t have to fear; then, this is not a dangerous condition. If it is properly treated, it will resolve completely.

(2) Piles (Hemorrhoids).

Piles or hemorrhoids are dilated (enlarged) blood vessels inside the wall of your anorectal canal. It usually occurs in people with frequent straining, like coughing and constipation. It also occurs in people who sit for long periods on the toilet.

The Symptoms Of Piles Are:

  • Painless bleeding with your stool; usually, the blood is bright red.
  • You may feel a skin tag or swelling around your anus.
  • Occasionally these dilated vessels get inflamed and cause continuous pain and itching around your anus.
  • The blood in stool with piles usually is silent with no other symptoms, and it may not be easy to diagnose by yourself.

blood in stool with IBS

What To Do If You Think You Have Piles With IBS:

  • Confirm the diagnosis by consulting your doctor; it will usually inspect your perianal area and do a ‘digital rectal examination’ or DRE.
  • Decrease straining by treating your constipation and eating softer foods.
  • Your doctor will usually describe pills and local creams to help with the piles; in certain cases, you may need surgery or a colonoscopy.

Read more about piles Here.

(3) Colon Polyps.

Colon polyps are usually very common (30% of Americans over 50 have colon polyps). So it is common to have both IBS and colon polyps causing blood in stool with your IBS.

Colon polyps are finger-like or cone-like projections from the lining mucosa of your colon. They are two types:

  • Inflammatory polyps are also called hyperplastic polyps, and it is usually harmless and has a low tendency to turn malignant.
  • An adenomatous polyp is a benign tumor with a relatively higher malignant potential, especially those with larger sizes.

The symptoms of colon polyps are:

  • Most commonly, colon polyps have NO symptoms.
  • However, blood in stool, especially with larger colon polyps or malignant ones, may get ulcerated and bleed.
  • The bleeding ranges from streaks of red blood in your stool to passage of large amounts of red blood or blackish tarry stool (melena).
  • Polyps can cause abdominal colics and iron deficiency anemia.

What to do If you think you have colon polyps:

  • Always consult your doctor. Usually, your doctor will do a colonoscopy or sigmoidoscopy to diagnose the condition.
  • Avoid a high-fat diet, and avoid eating too much meat.
  • Control your weight (if you are obese).
  • Gradually increase fiber in your diet.
  • Try to stop smoking and drinking alcohol.

(all of the above are risk factors for developing colon polyps).

For more information about colon polyps, click here.

(4) An Attack Of Dysentery.

A dysentery is a form of severe diarrhea associated with blood and mucus. Every IBS patient can have an attack of dysentery due to infections through contaminated food or water.

It is a common cause of blood in stool with your IBS.

There are two main types of dysentery according to the organism causing it:

  • Amoebic dysentery: is caused by an organism called entamoeba.
  • Bacillary dysentery: caused by a bacteria called shigella.

So how to know if you have dysentery?

  • Severe diarrhea with frequent attacks of diarrhea, you will continuously feel the urge to go to the bathroom, even every 5 minutes.
  • Diarrhea is mainly formed of mucus and blood.
  • Not related to eating (occurs all the time).
  • Associated with intense abdominal cramps
  • It may be nausea or vomiting.
  • Associated with fever.

What to do if you have dysentery:

Milder attacks of dysentery can resolve spontaneously. But if you have a fever or severe symptoms, you should visit your doctor.

Your doctor will usually prescribe antibiotics (to kill the organism causing dysentery), antispasmodics (to stop colics), and antipyretics (to control fever).

The best thing is not to get infected. Only drink water from reliable sources and eat adequately cooked food.

For more information about dysentery, click here.

(5) Inflammatory Bowel Diseases “Ibd”: (Crohn’s Disease Or Ulcerative Colitis).

Irritable bowel syndrome (IBS) completely differs from inflammatory bowel disease (IBD). IBS is a functional disorder. At the same time, IBD is a true disease that causes ulcers in your colon (ulcerative colitis) or any part of your gastrointestinal tract from the mouth to the anus (Crohn’s disease).

The misdiagnosis of IBD as IBS is common, especially with milder forms of IBD. If you have “RECURRENT” blood in your stool with your IBS, you have to reconsider the diagnosis of IBS with your doctor.

How to know if you have IBD, not IBS:

  • The colics and diarrhea are not related to meals and can occur at any time
  • Presence of blood in your stool (or mucus).
  • Nocturnal diarrhea: unlike IBS, IBD can wake you up after getting sleep with abdominal pain and an urge to poop.
  • Fever or weight loss.

If your doctor suspects inflammatory bowel disease, he will initially ask for some laboratory investigations and also will ask to do a colonoscopy for you.

IBD is a bad disease and may cause complications if left untreated. The treatment is usually a “Mesalazine,” and we can use other drugs like Corticosteroids and even surgery in severe cases.

For more information, watch this video from the “Discover Therapies” Youtube channel or click here.

(6) Colon Cancer.

Colon cancer is not uncommon nowadays. Colon cancer may cause blood in stools. IBS itself is not a risk factor for colon cancer. But with older ages, the risk of colon cancer increases, and bloody stool is one of the most common signs of colon cancer.

Colon cancer vs. IBS, how to differentiate?

  • Abdominal pain is not common in colon cancer, and if present, is a constant dull pain not related to meals. However, the IBS pain is related to meals and in the form of colics.
  • Sense of rectal mass or lump.
  • Bleeding with stool (red or dark blood)
  • Anemia and weight loss.

The “American Cancer Association recommends screening for colon cancer above the age of 45.” If you suspect colon cancer, you should immediately consult your doctor.

You can read in detail how to suspect, screen, and prevent colon cancer while you have IBS here.

(7) Other Rare Causes:

Bleeding Tendency:

When your blood becomes less able to make a clot as normal, it results from various diseases and drugs. The most common are

  • Immune thrombocytopenic purpura (low platelet count).
  • Drug overdose from “warfarin” is usually used to prevent thrombosis, as with people with valve replacements in their hearts.
  • Haemophilia and von Willebrand disease: are the other two bleeding disorders, but they usually don’t cause blood in the stool.

Angiodysplasia (Fragile Blood Vessels):

The presence of some fragile blood vessels inside the wall of your colon or any part of your gut track can lead to bloody stool. The conditions usually have no symptoms except for bloody stool or vomiting of blood (if the angiodysplasia is inside the stomach.

The condition is diagnosed by colonoscopy and endoscopically treated by laser coagulation and rarely needs surgery.

Diverticular Disease.

A rare condition where there are multiple sacs in the wall of your colon. These sacs can get inflamed (diverticulitis) and cause bloody stool. The condition is usually diagnosed by colonoscopy.

Bleeding from peptic ulcer or esophagus:

Gastritis and peptic ulcers are commonly associated with IBS. Bleeding from an ulcer in the wall of your stomach or duodenum will cause vomiting of blood (hematemesis) or passage of blackish stool, which is digested blood (melena). 

In certain cases where the bleeding is severe, there may be reddish blood in large amounts. This is because the blood doesn’t have enough time to be digested and turn black.


Take-Home Messages

  • Blood in stool is not a feature of IBS.
  • It either occurs secondary to IBS constipation causing fissures or piles, or occurs due to other conditions present together with IBS.
  • Blood in stool is not a thing you can ignore; 99% of its causes require you to consult your doctor.
  • Colon cancer is one of the causes of blood in the stool; if you are older than 40, have significant weight loss, or have anemia, you should screen for colorectal cancer immediately.
  • The three most common causes of blood in stool with IBS are:
    • Associated piles.
    • Associated anorectal fissure with IBS-constipation.
    • Attack of dysentery.