Mucus in stool is an often-overlooked symptom, yet it can hold valuable clues about gut health. While the gastrointestinal (GI) tract naturally produces mucus to protect and lubricate its lining, noticeable amounts in stool may signal an underlying issue. In the United States, GI diseases account for over 100 million outpatient visits and $142 billion in total costs every year, and abnormalities like mucus in stool can be an early indicator of these conditions.
Continue reading to learn about the common causes of mucus in stool, its clinical significance, and what to do about it.
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What Is Mucus in Stool?
Mucus is a slippery, jelly-like substance produced by certain types of cells that line the surfaces of organs exposed to the external environment.
Mucus is composed of:
- Water: The primary component, making up about 95% of mucus.
- Mucins: Proteins that are the primary structural and functional components of mucus and responsible for its gel-like consistency.
- Electrolytes: Contribute to the osmotic balance of pH of mucus.
- Lipids: Contribute to the viscoelastic properties and surface tension of mucus.
The Role of Mucus
In the digestive tract, mucus serves various functions (34, 35):
- Protection: Mucus forms a physical barrier that protects the epithelial cells lining the GI tract from mechanical damage, pathogens, and toxins, preventing infection and inflammation.
- Lubrication: Mucus facilitates the smooth passage of food and waste through the digestive tract by reducing friction.
- Immune Function: Mucus contains immune molecules, such as immunoglobulins (e.g., IgA), antimicrobial peptides, and enzymes, which help neutralize pathogens and modulate the immune response.
Normal vs. Abnormal Mucus in Stool
Nearly 10 liters of mucus are secreted into the GI tract every day, so it is normal for small amounts to be present in stool. In most cases, a person is unlikely to notice it.
However, visible mucus in stool can be a sign of digestive health concerns. Other signs and symptoms that may accompany it include:
- Copious amounts of mucus in stool
- Blood or pus in the stool
- Stomach pain, gas, or bloating
- Changes in stool frequency, consistency, or color
Causes of Mucus in Stool
If a person notices mucus in their stool, it could indicate one of the following underlying causes:
Irritable Bowel Syndrome (IBS)
IBS is a functional gastrointestinal disorder characterized by chronic abdominal pain or discomfort associated with altered bowel habits, such as diarrhea (IBS-D), constipation (IBS-C), or a mix of both (IBS-M).
Aside from abdominal pain and changes in bowel movements, other symptoms of IBS include:
- Bloating
- Sensation of incomplete bowel movements
- White mucus in stool
Mucus in stool in IBS patients is often due to a combination of altered mucosal barrier function, immune activation causing low-grade inflammation, and microbial dysbiosis.
Inflammatory Bowel Disease (IBD)
IBD is a chronic inflammatory condition of the gastrointestinal tract, primarily comprising two main subtypes: Crohn's disease (CD) and ulcerative colitis (UC). The excessive mucus in stool observed in IBD can be attributed to disruptions in the normal mucus barrier, mucus production, and goblet cell function.
Crohn's disease can affect any part of the GI tract from mouth to anus, often involving the full thickness of the bowel wall, and is characterized by skip lesions. Symptoms of CD include:
- Fatigue
- Abdominal pain
- Chronic diarrhea
- Constipation
- Unintentional weight loss
- Eye redness and irritation
- Mouth sores
Ulcerative colitis is limited to the colon and rectum and involves only the mucosal layer of the bowel. Symptoms of UC include:
- Chronic, watery diarrhea
- Blood in stool
- Abdominal and rectal pain
- A frequent urge of needing to have a bowel movement without being able to go
Intestinal Infections
GI infections can result from bacteria, viruses, or parasites. When pathogens invade the gut, they disrupt the protective mucus layer and irritate the epithelial cells lining the intestines. This irritation triggers goblet cells to increase mucus production as a protective mechanism. The excess mucus serves several functions: it traps and helps expel pathogens, protects the damaged tissue, and aids in restoring the integrity of the gut barrier. (21, 22)
Pathogens like Escherichia coli and Giardia duodenalis can directly target and degrade the mucus layer, exacerbating its disruption and leading to increased mucus secretion.
Other symptoms that may accompany mucus in stool during an intestinal infection include:
- Diarrhea
- Abdominal pain
- Nausea
- Vomiting
- Blood in the stool
- Fever
- Body aches
- Headache
- Fatigue
Food Sensitivities
Food sensitivities is an umbrella term encompassing a range of adverse reactions to certain foods. Adverse food reactions can be further categorized as:
- Food Allergy: An immediate immune response against a food protein, mediated by IgE proteins. Peanut allergy is one such example. (36)
- Food Intolerance: An inability to digest a specific food due to a digestive enzyme deficiency, such as lactose intolerance.
- Food Hypersensitivity: An IgG-mediated delayed immune response to a food protein that develops over hours to days (12).
Although these conditions involve different mechanisms, they all can negatively impact the integrity and function of the GI tract. When the body reacts to a food it perceives as harmful, inflammation often occurs in the digestive tract, leading to excessive mucus production as the gut attempts to protect and repair itself. Similarly, in food intolerances, the undigested food component can irritate the gut lining and trigger mucus secretion as a protective mechanism.
Intestinal Blockage
An intestinal blockage, or bowel obstruction, occurs when the normal flow of contents through the intestines is wholly or partially disrupted. This can happen in the small intestine, large intestine, or both, preventing food and waste from moving through the digestive tract. Partial obstructions may allow mucus or liquids to pass.
Bowel obstructions can be caused by various factors, including physical obstructions like scar tissue (adhesions) from prior surgeries, hernias, tumors, or impacted stool. Inflammatory conditions such as Crohn's disease can also lead to narrowing of the intestines (strictures) that obstruct passage.
Other symptoms that may indicate an intestinal blockage include:
- Abdominal pain that initially comes in waves and then becomes constant
- Bloating
- Nausea and vomiting
- Loss of appetite
- Malaise
- Diarrhea (partial blockage) or constipation (complete blockage)
Colorectal Cancer
Colorectal cancer is a malignancy that arises in the colon or rectum. As tumors grow, they can irritate the intestinal lining and cause bowel obstruction. Additionally, the tumor itself may secrete mucus, especially in cases of mucinous adenocarcinoma, a subtype of colorectal cancer characterized by the production of large amounts of mucus.
The presence of mucus in stool in colorectal cancer is often accompanied by other symptoms:
- A change in bowel habits, such as diarrhea, constipation, or narrowing of stool
- A constant urge of needing to have a bowel movement
- Blood in the stool
- Abdominal pain
- Fatigue
- Unintentional weight loss
When to See a Doctor
It's normal to see small amounts of mucus in stool occasionally. However, prolonged periods of excess mucus in stool, especially when accompanied by other concerning symptoms, may indicate an underlying health issue that requires medical evaluation.
Talk to a doctor if you experience any of the following symptoms along with mucus in stool:
- Persistent or severe abdominal pain
- Bright red blood in the stool or stools that appear black or tarry
- Persistent changes in bowel habits, such as diarrhea or constipation
- Unexplained weight loss
- Fever
- Fatigue
Diagnosis and Tests for Mucus in Stool
When investigating mucus in stool, healthcare providers typically begin with a comprehensive review of symptoms, personal health history, and family health history, as some conditions, like colorectal cancer, may run in families.
Diagnostic testing is then tailored to identify potential causes:
- Blood tests to assess for systemic signs of infection, inflammation, or food sensitivities
- Stool Culture and Other Stool Tests: A stool sample is analyzed to detect bacterial, viral, or parasitic infections. These tests can also reveal signs of intestinal inflammation or digestive enzyme deficiencies that may contribute to symptoms.
- Fecal Occult Blood Test (FOBT) or Fecal Immunochemical Test (FIT): These tests examine stool samples for hidden traces of blood, which may indicate inflammation, ulcers, or more serious conditions like colorectal cancer.
- Breath Tests: These are used to detect certain GI conditions, such as small intestinal bacterial overgrowth or malabsorption disorders like lactose intolerance.
- Colonoscopy or Sigmoidoscopy: These endoscopic procedures involve using a thin, flexible tube with a camera to visually inspect the colon and rectum. They can identify abnormalities like polyps, ulcers, or inflammation, assisting in the diagnosis of conditions like IBD and colorectal cancer.
Treatment Options
Treatment for mucus in stool depends on your diagnosis.
For mild cases, such as those caused by food sensitivities, lifestyle and dietary changes are often sufficient in resolving the issue. Treatment recommendations may include:
- Starting a 4-6 week elimination diet, followed by a systematic food rechallenge to identify trigger foods
- Eating probiotic-rich foods or taking probiotic supplements to support a healthy gut microbiome
- Staying well hydrated by drinking adequate amounts of water. A general rule of thumb is to drink half of your body weight in ounces of water daily.
- Eating a diet rich in vegetables, fruits, whole grains, nuts, and seeds to meet recommended dietary fiber intake goals of 25-35 grams daily.
Intestinal infections should be treated with prescription or natural antimicrobials (e.g., antibiotics, antivirals, and antiparasitics).
Ongoing treatment with prescription medications and natural supplements may be required to treat chronic GI conditions, such as IBS and IBD. Sample treatment protocols are available through the Rupa Health Magazine:
- Functional Medicine IBS-D Protocol: Testing, Differential Diagnosis, and Treatment
- A Functional Medicine Crohn's Disease Protocol: Specialty Testing, Nutrition, and Supplements
- A Functional Medicine Ulcerative Colitis (UC) Protocol: Testing, Nutrition, and Supplements
Bowel obstruction requires prompt treatment in the hospital. Complete obstructions require emergency surgery to correct. Partial obstructions can usually be treated with intravenous fluids, bowel rest, and palliative care to help patients feel more comfortable. (3)
If you are diagnosed with colorectal cancer, you will be referred to an oncologist for treatment. Treatment options will depend on the stage at which the cancer is diagnosed but typically include surgery and chemotherapy. (13)
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Key Takeaways
- In most cases, mucus in stool is a normal part of digestion and goes unnoticed.
- However, when larger amounts of mucus become visible, especially over a prolonged period or alongside other symptoms, it may signal an underlying issue ranging from minor concerns to more serious conditions.
- If you notice unusual mucus in your stool or other concerning symptoms, consulting a healthcare provider is the best course of action. They can review your medical and dietary history, conduct a physical exam, and order appropriate tests, such as stool analysis or imaging, to identify the cause and recommend treatment.
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