Giardia Poop: Color, Smell, & How it Looks (Doctor Explains).

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1. Key Facts:

Giardiasis poop typically looks yellowish or grey in color, bulky, offensive, or fishy-smelling in odor. In About 90% of the cases, the stool is usually loose or watery; However, hard stool (constipation) may be found in a minority of patients.

  • Giardiasis stool color: is often yellowish, yellowish-brown, or greyish.
  • Giardiasis stool smell is often very offensive or fishy-smelling.
  • Giardiasis stool is typically watery or loose. However, constipation may also occur.
  • Giardiasis stool smell and color are NOT specific to the disease. Many other diseases may cause identical stool changes, such as chronic pancreatitis and celiac disease.
  • The diagnosis of giardiasis depends mainly on visualizing the Giardia cysts by microscopy, stool antigen tests, and PCR tests.

2. What does giardia poop look like?

Giardiasis poop typically looks yellowish or grey in color, bulky, offensive, or fishy-smelling in odor. In About 80% of the cases, the stool is usually loose or watery; However, hard stool (constipation) may be found in a minority of patients.

Here is a breakdown of all the possible forms, colors, and smells of acute and chronic Giardiasis in humans:

A. Giardia stool smell.

People who get giardiasis infection often experience severe malabsorption as the organisms destroy the small intestinal mucosa responsible for absorption.

Giardia-induced malabsorption leads to the accumulation of fats and sugar in the gut, leading to offensive or fishy-smelling stools.

Patients may describe odors, such as rotten eggs, sulfur smell, rotten meat, etc.

Acute and chronic giardiasis infections lead to offensive stool. However, the stool smell is notably more offensive in the chronic form of the disease.

Giardiasis-related malabsorption leads to foul-smelling poop, profound weight loss, fatty or oily stool, and stunted growth in children.

B. Giardia stool color.

Giardia stool is typically yellow, yellowish-brown, or grey (pale). These stool color changes result from acquired lactose and fat malabsorption associated with acute and chronic giardiasis.

Giardia yellow poop can be confused with norovirus yellow stool (the most common cause of acute diarrhea).

The yellowish or greyish color of the Giardia poop is due to:

  • Presence of more fat in the poop (giardia leads to fat malabsorption).
  • More water in the stool (The non-absorbed food draws water into the intestine).
  • Speeding up of the stool in the gut of giardia patients

C. Giardia stool frequency.

Giardiasis predominantly causes diarrhea (More than three bowel movements per day of loose or watery stool). However, some giardia infections pass without symptoms (normal bowel movements). A minority may present with constipation.

In symptomatic acute giardiasis, the stool frequency may be:

  • Diarrhea (in about 90% of the cases).
  • Constipation (in up to 13% of the cases).

In symptomatic cases of chronic giardiasis, the loose stool is the predominant symptom (rather than diarrhea).

D. Can you see the Giardia organism in poop?

The average Giardia cyst shed in stool is about [10-14 micrometers]( duodenalis cysts are oval,while immature cysts have two.) which are very small to be detected by the naked eye. Giardia cysts’ size is about one-fifth the thickness of the average human hair. So, you Can’t see Giardia organisms in poop.

The cysts are detected only by microscopic stool examination (stool analysis). It appears as oval or ellipsoid cysts with 2-4 nuclei within.

3. Is Giardiasis poop specific for the disease?

Unfortunately, The foul or fishy-smelling & fatty stool is not specific to Giardiasis. Many other diseases and infections may cause similar stool changes.

For example, lactose intolerance and acute pancreatitis patients have stool changes almost identical to giardiasis.

So, you cannot depend on these stool changes to diagnose giardiasis. And the diagnosis of giardiasis depends on a combination of:

  • Characteristic symptoms.
  • Characteristic stool changes.
  • Exclusion of other causes of steatorrhea.
  • Laboratory diagnosis of the disease.

A. Symptoms of acute giardiasis:

  • Acute onset diarrhea (greasy, yellowish, or light brown).
  • Sudden abdominal cramps and pain.
  • Foul or fishy-smelly watery diarrhea occurs in up to 75% of cases of acute giardiasis.
  • Malaise and fatigue (in 86% of the cases).
  • Bloating.
  • Flatulence and excess gas.
  • Nausea (69%).
  • Vomiting (in 23%).
  • Fever in 15%.
  • Sometimes, constipation.
  • Skin itching (urticaria).
  • Many people may get giardiasis infection without any symptoms.
  • The symptoms (including fishy-smelling watery diarrhea) often last one to four weeks.

B. Symptoms of chronic giardiasis:

The symptoms often come and go, in the form of:

  • Loose stools but usually no diarrhea
  • Steatorrhea
  • Profound weight loss (10 to 20 percent of body weight)
  • Malabsorption
  • Stunted growth
  • Malaise
  • Fatigue
  • Depression
  • Abdominal cramping
  • Borborygmi
  • Flatulence
  • Burping

C. Laboratory diagnosis:

  • Stool analysis (microscopy) to see the Giardia cysts.
  • Stool antigen tests.
  • PCR (polymerase Chain Reaction) for Giardia in the stool.

4. Mimics of giardiasis stool.

The following condition may mimic either stool color, smell, or diarrhea from giardiasis. We classified them into acute and chronic depending on the time frame of the stool changes.

  • Acute giardiasis leads to diarrhea and stool changes lasting less than four weeks (Average giardiasis symptoms last for about 18 days).
  • Chronic diarrhea or loose stool usually waxes and wanes for months or even years.

A. Mimics of chronic giardiasis stool:

  • Lactose intolerance.
  • Other forms of food intolerance.
  • Celiac disease.
  • Chronic pancreatitis.
  • Other forms of chronic infections such as Clostridiodes difficile infection.
  • SIBO.
  • Bile acid diarrhea.
  • Inflammatory bowel disease (chron’s disease and ulcerative colitis).

B. Mimics of acute giardiasis stool:

  • Bacterial gastroenteritis.
  • Stomach flu (viral gastroenteritis).
  • Food poisoning.
  • Recent antibiotics.

5. Treatment of giardiasis poop changes.

  • Anti-protozoal medication such as Tinidazole, nitazoxanide, or metronidazole (Flagyl®) is the definitive treatment of the disease. After treatment, your stool should gradually revert to its normal consistency, color, and smell.
  • Drink plenty of fluids.
  • Avoid high-fat foods.
  • Eat bland, easy-to-digest foods such as the BRAT diet (bananas, rice, apple sauce, and toast).
  • OTC medicine to stop diarrhea, fever, and abdominal pain may also help in severe cases (such as Immodium®).
  • Giardiasis may become chronic in some patients; a visit to your doctor is essential if you have symptoms consistent with chronic giardiasis.