Is Mushy Stool a Sign of Colon Cancer? (When to Worry?)

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Mushy or loose stool can be a sign of colon cancer. However, it is not a specific symptom and can occur in various conditions such as IBS and food intolerance. Search for other suspicious symptoms such as the passage of dark stool, weight loss, anemia, etc.

This article will explore all the possible links between mushy stool and colon cancer and will dive in red-flag signs that you should know.


Table of Contents

1. Colon cancer is a rare cause of mushy stool.

Mushy stool is a common symptom of mushy stool. Change in bowel habits (constipation, diarrhea, or mushy stool) affects 75% of patients with colorectal cancer (reference)

However, constipation, diarrhea, and mushy stool happen to a thousand different causes, making colon cancer a rare cause of mushy or loose stool.

It would help if you considered mushy stool a cause of colon cancer when other symptoms and risk factors of colon cancer (explained later).

The colorectal cancer

Acute Vs. Chronic attacks of mushy stool:

A single or few acute attacks of mushy stools are unlikely to be a sign of colon cancer. However, colon cancer patients often experience chronic or frequent attacks for weeks or months.

There is no need to worry about an acute attack of diarrhea or mushy stool that lasts for a few days or weeks.

Bloody or blackish mushy stool:

Mushy stool with brown or yellowish color (especially if acute) is rarely a sign of colon cancer.

However, when a change in bowel habit (diarrhea or mushy stool) is associated with bleeding (red or blackish stool), the probability of colorectal cancer is much higher.

Bleeding in the stool (red blood, blackish stool, or black spots in the stool) is found in 50% of patients with colon cancer (reference).

2. When is mushy stool less likely to be a colon cancer sign?

Don’t overthink mushy stool as a cause of bowel cancer as long as:

  • The attacks are infrequent. 
  • You don’t have other symptoms of colon cancer, such as blood in stool, weight loss, and anemia.
  • You are younger. 
  • You don’t have a family history of colon cancer
  • You are lean (not obese).
  • You are not a smoker, and don’t overconsume red meat. 
  • You are physically active.

3. When is mushy stool likely a sign of colon cancer?

As we explained above, Mushy stool is a widespread complaint. It can result from diseases or conditions 1000x more common than colon cancer, such as intolerance to certain foods or IBS.

For the mushy stool to be a sign of colon cancer, it has to be associated with the following:

  • Risk factors of colon cancer.
  • Other signs and symptoms of colon cancer.

Risk factors of colon cancer include:

  • Being older (above 45 years old. More than 90% of the cases of colon cancer are above the age of 50).
  • Family history of colon or rectal cancer (a significant risk factor for colon cancer even in younger generations)
  • Obesity.
  • Eating red and processed meat.
  • Diabetes Mellitus at a young age.
  • Alcohol drinking.
  • Tobacco smoking.
  • Physical inactivity. 

The associated symptoms of colon cancer and its relation to mushy stool are discussed next.

4. The most common symptoms of colon cancer.

To give you an overview of the common symptoms associated with colon cancer, look at the list below. Search shows the percentage of each symptom in colon cancer (source):

1. constipation or diarrhea(or mushy stool)

  • occurs in 75% of colon cancer patients.
  • It often persists for several weeks, months, or even years.

2. Bleeding:

  • Bleeding can be in bright red blood in the stool, Black tarry stool, or black spots in the stool.
  • It affects 50% of colon cancer patients.
  • When the mushy stool color is mixed with blood (reddish or black), It raises the suspicion of colon cancer.

3. Rectal mass:

  • In 25% of the cases of colon cancer.
  • It causes a sense of incomplete evacuation and a persistent urge to defecate.

4. Anemia symptoms:

  • It affects 10% of colorectal cancer patients at the time of presentation.
  • Some patients may not have frank bleeding in the stool (black or red stool).
  • Persistent minor bleeding may lead to a severe form of iron deficiency anemia.
  • Symptoms include easy fatigue, headache, dizziness, shortness of breath, and fast heartbeats.

5. Isolated abdominal pain

  • Isolated abdominal pain with no other symptoms is rare with colon cancer; it is only found in  3.8% of colon cancer patients.
  • The more common scenario is abdominal pain associated with other red flag symptoms (anemia, weight loss, blood in stool, and recent change in bowel habits in ages above 50).

6 . Other symptoms of colon cancer:

  • Unexplained weight loss.
  • Nausea.
  • Loss of appetite.
  • Nighttime abdominal pain.
  • Unexplained fever.
  • Metastatic colon cancer can present with various symptoms, such as liver pain, bone pain, and loss of consciousness.
  • Sings of complicated colorectal cancer include intestinal obstruction (severe abdominal distention, constipation, and vomiting), Infection, or fistula formation.

MORE:4 Stool Changes in Stage 1 Colon Cancer (with Pictures).

5. The most common causes of mushy stool.

A. Diet.

Loose or mushy stool attacks now and then are often due to dietary effects. For example, high fat, fructose, and high lactose diet may cause alternation in the stool form.

B. Infections.

Mild digestive system infections such as mild viral gastroenteritis or mild forms of food poisoning may lead to acute diarrhea or mushy stool.

C. Food intolerance.

About 15 to 20% of people worldwide are intolerant to certain types of food.

The most common types of food intolerance are lactose intolerance, FODMAP intolerance, fructose, and caffeine intolerance.

D. Irritable bowel syndrome.

Irritable bowel syndrome (IBS)is one of the most common functional digestive system disorders affecting 15% of people worldwide.

People with IBS experience recurrent abdominal pain (at least one day per week), changes in bowel habits (such as diarrhea or constipation), and changes in the stool form (including mushy stool).

Learn more about IBS and how it is diagnosed here.

E. Infections.

Any acute and chronic digestive system infection can lead to mild diarrhea conditions (only loose or mushy stool). In addition, mild attacks of food-borne illnesses (food poisoning) can lead to mushy stool.

F. Celiac disease.

Celiac disease is an immune-mediated reaction to a protein called gluten (found in wheat, rye, and barley). Patients with celiac disease suffer from chronic diarrhea or mushy stools, anemia, weight loss, and abdominal pain. Learn More.

G. Inflammatory bowel diseases (IBD).

An inflammatory bowel disease is a group of diseases of unknown cause. They include Crohn’s disease and ulcerative colitis. With IBD, chronic inflammation and ulceration of the digestive tract lead to chronic diarrhea or mushy stool. Other symptoms include abdominal pain, blood in the stool, weight loss, and unexplained fever.

H. Others (less frequent).

  • Stress-related diarrhea (anxiety and fear).
  • Chronic use of certain medications such as metformin.
  • Endocrinal diseases such as hyperthyroidism (hyperactive thyroid gland).
  • Chronic laxative abuse.
  • SIBO.
  • Neuroendocrine disorders such as carcinoid syndrome.
  • Colorectal cancers.
  • Chronic pancreatitis.

MORE: 8 Common Causes of Mushy Stool & Gas.