What Causes Red Blood In Stools?

Red blood in stools can have various causes, ranging in severity from 'worrying' to 'generally fatal'. Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.

Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms. In order to diagnose red blood in stools, we could:

Research the topic
Find a doctor with the time
Use a diagnostic computer system.

The process is the same, whichever method is used.

Step 1: List all Possible Causes

We begin by identifying the disease conditions which have "red blood in stools" as a symptom. Here are eight possibilities (more below):

Stomach Ulcers
Iron Deficiency Anemia
Crohn's Disease
Hemorrhoids
Possible Urgent Medical Need
Ulcerative Colitis
Gastrointestinal Bleeding
Colon Cancer

Step 2: Build a Symptom Checklist

We then identify all possible symptoms and risk factors of each possible cause, and check the ones that apply:

black/tarry stools

colitis in family members

epigastric pain

recent breastfeeding

very low serum iron

past and future vaccination

slightly black/tarry stools

anal itching

discontinued low-carb diet

microcytic red cells

regular painful urge to defecate

stiff neck

... and more than 60 others

Step 3: Rule Out or Confirm each Possible Cause

A differential diagnosis of your symptoms and risk factors finds the likely cause of red blood in stools:

Cause	Probability	Status
Ulcerative Colitis	92%	Confirm
Stomach Ulcers	12%	Unlikely
Iron Deficiency Anemia	14%	Unlikely
Crohn's Disease	1%	Ruled out
Gastrointestinal Bleeding	1%	Ruled out
Colon Cancer	0%	Ruled out
Hemorrhoids	0%	Ruled out
Possible Urgent Medical Need	0%	Ruled out

* This is a simple example to illustrate the process

Arriving at a Correct Diagnosis

The Analyst™ is our online diagnosis tool that learns all about you through a straightforward process of multi-level questioning, providing diagnosis at the end.

If you indicate irregular stools, The Analyst™ will ask further questions including this one:

Do you see red blood in or on your stools?

Possible responses:

→ Never / don't know
→ Occasionally / small amount on tissue only
→ Occasionally / small amount on tissue and stool
→ Very often recently
→ A significant amount for some time now

Based on your response to this question, which may indicate red blood in stools, frequent red blood in stools or significant red blood in stools, The Analyst™ will consider possibilities such as:

A Potentially Urgent Medical Need

Significant bleeding from anywhere in the body requires immediate medical attention. Small amounts of red blood, especially on the toilet tissue, are most likely from hemorrhoids.

Colon Cancer

In general, you should see a specialist if you are over 40 and have the following symptoms:

A change in normal bowel habits towards looser and/or more frequent stools that has lasted for over 6 weeks
Any bleeding from the rectum.

Crohn's Disease

Endometriosis

Gastric/Peptic/Duodenal Ulcers

Rapid bleeding can cause bowel movements to become black or even bloody.

Gastrointestinal Bleeding

Passing visible blood from the rectum (hematochezia) may indicate bleeding in the lower intestines.

Hemorrhoids

Iron Deficiency Anemia

Ulcerative Colitis

Ulcerative colitis can cause bloody, watery or mucousy bowel movements which may consist only of blood and pus.

Red Blood In Stools