Green stool is generally not a sign of liver cancer. It is more often a symptom of eating lots of green foods or food coloring, taking iron supplements, or digesting foods too quickly.

Stool that is an unusual color can be concerning but is not always a cause for alarm. Liver cancer can change the color of stools. However, it typically causes stools that are pale in color or tarry black.

This article outlines what causes green stool. It also describes how liver cancer and other liver problems can cause changes in stool color. Finally, it lists some symptoms of liver cancer and provides information on when to speak with a doctor.

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Liver cancer does not cause stool to turn green in color. Instead, the disease can cause stools to turn pale or black.

Pale stool

The liver contains bile ducts that release bile into the intestine to aid digestion. Bile contains a greenish-yellow substance called bilirubin, which contributes to the brown color of stool.

Bile duct cancer can impede the liver’s ability to release bile, meaning bilirubin does not reach the intestines. This can cause stools to appear lighter in color.

A lack of bile in the intestines also impairs a person’s ability to digest fatty foods. As a result, fats pass into the stools, causing them to be pale, bulky, and greasy. These stools may also float in the toilet.

Black stool

Metastatic liver cancer is a cancer that has originated in another part of the body and spread to the liver. This type of cancer can cause black stool.

According to the Canadian Society of Intestinal Research (CSIR), the following factors can cause green stool:

  • Diet: A common cause of green stool is a diet that is rich in green foods, such as leafy green vegetables, or foods and drinks containing green food coloring.
  • Iron supplements: Dark green stools can indicate unabsorbed iron. They are a common and harmless side effect of iron supplementation.
  • Rapid colon transit time (RCTT): Bile typically darkens as it passes through the digestive system but can remain green if it passes through too rapidly. As such, green stools can indicate that the stool is passing through the colon too quickly. An RCTT can be a symptom of inflammatory bowel disease (IBD).

Many stool colors relate to changes in diet, including medications.

According to the CSIR, the following stool colors may signal a problem with the liver:

  • Yellow: Yellow stools can indicate a problem with the production of bile salts.
  • Pale yellow, gray, or brown: Pale stools can signify a problem with the liver or gallbladder.

The typical stool has a brown color indicating the presence of bilirubin from bile. If the stool is not brown, it suggests that the digestive tract is not receiving or processing bile.

Symptoms of liver cancer often show in the late stages of the disease but sometimes appear earlier. Many of the symptoms also have links to other conditions. As such, anyone who experiences any of the below symptoms should consult a doctor for a diagnosis.

According to the American Cancer Society (ACS), symptoms of liver cancer include:

If the disease involves the bile ducts, a person may not be able to digest fats from their diet. This leads to pale stools, which may also float and be greasy and bulky.

Green stool is not generally a cause for concern. However, if green stools reoccur or cause worry, a person should contact a doctor for reassurance.

Anyone who experiences pale or dark stools or any other possible symptoms of liver cancer should contact their doctor for an appointment.

Some conditions can increase the risk of liver cancer. As such, some healthcare professionals recommend that people with any of the following conditions undergo screening for liver cancer every 6 months:

The outlook for an individual with green stool is positive since this symptom is usually due to dietary changes.

In some cases, green stool can indicate that the digestive tract is moving food through too quickly. This can be a symptom of IBD. Anyone who suspects they may have IBD should visit their doctor for a diagnosis and appropriate treatment. Some other possible IBD symptoms to look out for include:

Green stool is not a sign of liver cancer. Typically, liver conditions cause stool to turn pale in color or tarry black.

Green stools are usually the result of eating large quantities of green foods or consuming green food coloring. Iron supplements can also cause stools to turn dark green.

Symptoms of liver problems include abdominal swelling, feelings of fullness under the ribcage, itching, and jaundice. Anyone experiencing symptoms of liver cancer should speak with a doctor as soon as possible for a diagnosis.