Stool Odor

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What is stool odor?

Stool odor is the smell associated with stools, or bowel movements. Stools normally have an unpleasant odor.

Stools are formed in the large intestine (colon), which is part of the digestive system. Normally, “good bacteria” live in your large intestine and help digest or break down the food remnants that enter the large intestine from the small intestine. Stools are formed during this process. Stools are passed through the large intestine to the rectum for elimination from the body. The normal, unpleasant smell associated with stools is a result of the bacteria.

Changes in stool odor can be caused by the foods you eat. Even extremely foul-smelling stools can be due to changes in your diet. However, abnormally foul-smelling stools may also be a sign of a disease, disorder or condition. Examples include celiac disease, Crohn’s disease, cystic fibrosis, and intestinal infections. Because of the range of possible causes of bad stool odor, a correct diagnosis of the underlying disease, disorder or condition is very important. Contact your healthcare provider for a physical exam.

In some cases, foul-smelling stools may be a sign of a serious or life-threatening condition, such as an intestinal infection, abscess, or obstruction. Seek immediate medical care (call 911) if you have foul-smelling stools with serious symptoms, such as severe abdominal pain, cramping, and bloody stools.

Seek prompt medical care if your stool odor is unusual, unexplained or persistent, or causes you concern.

What other symptoms might occur with stool odor?

Foul-smelling stools may accompany other symptoms, which vary depending on the underlying disease, disorder or condition. Symptoms frequently affect the digestive tract but may also involve other body systems.

Digestive symptoms that may occur along with stool odor

Stool odor may accompany other symptoms affecting the digestive system including:

Other symptoms that may occur along with stool odor

Stool odor may accompany symptoms related to other body systems. Symptoms may include:

Symptoms that might indicate a serious or life-threatening condition

In some cases, foul-smelling stools may occur with other symptoms that might indicate a serious or life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have a foul stool odor and any of the following symptoms:

What causes stool odor?

Many different diseases, disorders and conditions can lead to foul-smelling stools. Foul-smelling stools can be a sign of inflammatory disorders, intestinal infections, malabsorption disorders, and inherited medical conditions.

Infectious causes of stool odor

Foul-smelling stools may arise from intestinal infections caused by viruses, bacteria and parasites including:

  • Clostridium difficile bacteria

  • Cryptosporidium parasites

  • E. coli bacteria

  • Giardia parasites

  • Salmonella bacteria

  • Shigella bacteria

Inflammatory causes of stool odor

Inflammatory causes of foul-smelling stools include:

Malabsorptive causes of stool odor

Foul-smelling stools may arise from malabsorption disorders in which your body does not absorb nutrients from food efficiently. Malabsorption disorders include:

  • Celiac disease (severe sensitivity to gluten from wheat and other grains that causes intestinal damage)

  • Short bowel syndrome (nutrients are not absorbed due to intestinal disease or surgery)

Inherited causes of stool odor

Foul-smelling stool is one possible symptom of cystic fibrosis, which is an inherited condition that causes thick mucus buildup in the lungs and digestive tract. Although most people with the disease are diagnosed before age two, some people are not diagnosed until young adulthood.

Serious or life-threatening causes of stool odor

In some cases, foul-smelling stools may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

Questions for diagnosing the cause of stool odor

To diagnose the underlying cause of foul-smelling stool, your doctor or licensed healthcare provider may ask you several questions related to your symptoms. You can best help your healthcare provider in diagnosing the underlying cause of your stool odor by providing complete answers to these questions:

  • When did your stool odor start?

  • What color are your stools? Are they lighter or darker than normal?

  • Do you have difficulty pushing or moving your stools?

  • What is your current diet? Have you made any recent changes in your diet?

  • Do you notice a change in your stool odor with any particular foods or drinks?

  • What are your other symptoms?

Your healthcare provider may request a stool sample to help in diagnosing the underlying cause of your stool odor.

What are the potential complications of stool odor?

Complications of foul-smelling stool depend on the underlying disease, disorder or condition. Identifying and treating the underlying cause of stool odor is important to minimize any potential complications. Because foul-smelling stool can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan you and your healthcare professional design specifically for you to reduce the risk of potential complications including:

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 16
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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