Red Blood In Stools

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.

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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
  • Crohn's Disease
  • Endometriosis
  • Colon Cancer
  • Iron Deficiency Anemia
  • Possible Urgent Medical Need
  • Ulcerative Colitis
  • Gastrointestinal Bleeding

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:
significant bowel movement changes
late birth of first child
meal-induced pain for 1-4 weeks
recent onset nausea
ulcerative colitis in remission
pain in one eye
moderate upper-right pain after food
moderate left iliac pain
Crohn's disease in remission
major unexplained weight loss
history of NSAID use
elevated ESR
... and more than 100 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 96% Confirm
Endometriosis 19% Unlikely
Gastrointestinal Bleeding 12% Unlikely
Possible Urgent Medical Need 0% Ruled out
Iron Deficiency Anemia 0% Ruled out
Colon Cancer 0% Ruled out
Stomach Ulcers 0% Ruled out
Crohn's Disease 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:
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.
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.

Ulcerative Colitis

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

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