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Could Persistent Diarrhea be a Symptom of Colorectal Cancer?

Medically reviewed by John Paul Abrina, MD · Oncology · Davao Doctors Hospital

Written by Lorraine Bunag, R.N. · Updated Sep 08, 2021

Could Persistent Diarrhea be a Symptom of Colorectal Cancer?

We often treat diarrhea as a disease. But the truth is, it could be a symptom of another health condition. In most cases, eating contaminated or spoiled food causes diarrhea. But did you know that something as serious as cancer could also cause loose, watery stool? In this article, we’ll answer the question: is chronic diarrhea a sign of cancer?

What is Chronic Diarrhea?

You are probably familiar with diarrhea. Chances are, you have experienced it at least once. However, while we understand that diarrhea is frequent, loose, and watery bowel movement, we need to clarify what it means when we add the word “chronic.”

Essentially, chronic means “long-term,” denoting that it has been happening for quite some time now. According to the American College of Gastroenterology, chronic diarrhea occurs when a person experiences frequent, runny stool for longer than 4 weeks.

Many doctors say that chronic diarrhea should be a cause of concern not only because of the complications it may bring (such as dehydration), but also because it could be a sign of a serious problem like cancer. When is chronic diarrhea a sign of cancer? Read on to find out.

When is Chronic Diarrhea a Sign of Cancer

At this point, you might be wondering: how can something as simple as loose, watery stool develop from a serious condition like cancer? When is chronic diarrhea a sign of cancer?

For starters, runny stool may happen due to the presence of a tumor in areas near the organs responsible for bowel movement. When is chronic diarrhea a sign of cancer? One example is rectal cancer. When a person has a tumor in their rectum, it may change the consistency, frequency, and shape of the stool. This results in loose bowel movement.

There are also instances when poor absorption of food causes diarrhea, as in the case of pancreatic cancer. Our pancreas is responsible for releasing enzymes that help break down fatty food. The growth of a tumor in the pancreas may block the pancreatic ducts, causing the insufficiency of enzymes in the intestine. With limited enzymes to break down fats, the food will not be absorbed well and diarrhea may occur.

Finally, cancers in the organs responsible for bowel movement may also cause diarrhea.

Chronic diarrhea a sign of cancer

What Types of Cancer Cause Diarrhea?

Now that we have established the answer to: is chronic diarrhea a sign of cancer?

You must be wondering: what cancers cause diarrhea? Here’s a brief list of common cancers that present with diarrhea:

  • Colon cancer
  • Rectal cancer
  • Pancreatic cancer
  • Lymphoma
  • Medullary carcinoma of the thyroid gland

Carcinoid syndrome may also cause loose, watery stool. Carcinoid syndrome happens when a person develops a carcinoid tumor, a special type of tumor that releases chemicals in the bloodstream. The common sites where a carcinoid tumor grows are the lungs and gastrointestinal tract.

When to Seek Medical Help

Since diarrhea is such a common condition, many people do not consult a doctor when they experience it. However, now that you understand that diarrhea can be a cancer symptom, you must be more observant.

Go to the doctor right away if you:

  • Are suffering from 6 or more loose, watery stool in a day for 2 days or more
  • Have dizziness while suffering from diarrhea
  • See blood in your stool or your rectal area
  • Have diarrhea or cramps for more than a day
  • Are already experiencing weight loss due to diarrhea
  • Develop difficulty in controlling your bowel movement
  • Develop a fever of 38 C or higher
  • Remember that diarrhea, especially when it’s chronic, can lead to severe dehydration. For this reason, seek medical help if you suspect signs of dehydration such as dark urine, dry skin, sunken eyes, and rapid breathing and heartbeat.

    Additionally, talk to your doctor, too, if your diarrhea is making it difficult for you to perform activities of daily living.

    How to Cope with Diarrhea

    To help manage your diarrhea, you can take the following measures:

    • Have small, frequent meals throughout the day instead of heavy ones.
    • Drink clear fluids such as water, clear broth, and apple juice.
    • Avoid foods that trigger the worsening of your symptoms. This may include alcohol, spicy food, fatty food, and dairy.
    • Consider taking probiotics as they may help restore normal digestion.
    • When your diarrhea shows signs of improvement, add low-fiber foods to your diet.

    Despite all these measures, your topmost priority is to determine the condition that’s causing your loose bowel movement. Thus, visiting the hospital for a thorough physical assessment is a must.


    Although we have just talked about chronic diarrhea as a sign of cancer, it’s crucial to understand that, in most cases, diarrhea comes with other bowel changes.

    Let’s take this scenario: a patient with colon cancer may have bouts of alternating constipation and diarrhea. This means that for a certain period, they’ll suffer from difficulty in passing stool, and then they’ll experience loose, watery bowel movement.

    Other times, patients may notice something different with their stool, like it becoming thinner or changing color. For example, black stool may indicate that there’s bleeding in the digestive tract and that the blood has dried, causing it to darken.

    Ultimately, it is crucial to be attentive to the changes in your body. If you notice any change and feel that nothing in your lifestyle or diet is causing it, talk to your doctor right away.

    Key Takeaways

    Is chronic diarrhea a sign of cancer? It turns out that it can be, especially when it’s chronic and accompanied by other bowel changes. With chronic diarrhea, the rule of thumb is to prevent dehydration and determine its root cause. You can achieve the latter by talking to a doctor for proper assessment.

    Learn more about Cancer here


    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Medically reviewed by

    John Paul Abrina, MD

    Oncology · Davao Doctors Hospital

    Written by Lorraine Bunag, R.N. · Updated Sep 08, 2021

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