Villous Atrophy: Definition

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Villous atrophy means the villi in the small intestine lining have become shorter or flattened. Villi are tiny, finger-like projections that absorb nutrients from food. When they shrink, the intestine absorbs less. Celiac disease is the best-known cause, but other conditions can cause it too.

Villous atrophy is a finding, not a diagnosis. It describes what the pathologist saw under the microscope. This article explains what villous atrophy means, what causes it, how pathologists identify it, and what the wording on your report means.

What are villi?

Villi are the tiny, finger-like projections that cover the inside of the small intestine. Together they form a large surface that absorbs nutrients. They sit in the mucosa, the inner lining of the bowel. Small pits called crypts lie between the villi. The small bowel mucosa article describes this lining in more detail.

What does villous atrophy mean?

Villous atrophy means the villi have lost height. Atrophy is the medical word for shrinkage. In villous atrophy, the villi become short or disappear altogether. The lining then looks flat under the microscope. A flat lining has far less surface area for nutrient absorption.

Pathologists describe the change as mild, marked, or total. The modified Marsh classification uses these steps for celiac disease. Type 3a means mild atrophy, type 3b means marked atrophy, and type 3c means total atrophy with completely flat villi.

How is villous atrophy different from villous blunting?

Villous atrophy is a more severe change than villous blunting. With blunting, the villi are shorter or flatter but still present. With atrophy, the villi are very short or gone. Many reports use blunting for the milder change and atrophy for the more severe change.

What causes villous atrophy?

Villous atrophy has many causes. A biopsy alone often cannot show which one applies, because several conditions look alike under the microscope. The main causes are:

Celiac disease. Celiac disease is an autoimmune reaction to gluten, a protein in wheat, barley, and rye. The immune system damages the small intestine lining.
Medications. Olmesartan, a medicine for high blood pressure, can cause a condition that looks like celiac disease. Symptoms and biopsy changes improve after a person stops taking the drug. Your doctor, not your pathology report, decides whether to change a medicine.
Infections. Some infections damage the villi. Examples include giardiasis, a parasite infection, and tuberculosis. HIV can also cause this change. Damage can also follow a viral infection of the bowel.
Inflammatory conditions. Crohn’s disease can involve the small intestine and flatten the villi. So can eosinophilic gastroenteritis, which is inflammation of the bowel caused by white blood cells called eosinophils.
Immune conditions. Common variable immunodeficiency is a condition in which the body makes too few antibodies. Autoimmune enteropathy is a rare condition in which the immune system attacks the bowel lining. Both can cause villous atrophy.
Other causes. Food allergies and radiation treatment to the abdomen can also injure the villi.

What other changes do pathologists look for?

Pathologists look for other changes in the same biopsy to help find the cause of villous atrophy. The pattern of changes is a clue, but it does not settle the question alone. Three findings are common:

Intraepithelial lymphocytes. These are white blood cells inside the surface lining. Intraepithelial lymphocytosis means there are too many. Many pathologists use a cutoff of 25 for every 100 surface cells. Celiac disease and olmesartan injury can both raise the count.
Crypt changes. In celiac disease, the crypts grow larger and more numerous as the bowel tries to repair itself. Pathologists call this crypt hyperplasia.
Inflammation. The pathologist checks the lamina propria, the layer of tissue under the surface lining, for inflammation. Inflammation can help point to a cause.

How is villous atrophy identified?

The pathologist identifies villous atrophy by studying a biopsy under the microscope. The doctor usually takes the samples during an endoscopy. In this procedure, the doctor passes a thin camera through the mouth into the stomach and the first part of the small intestine, called the duodenum. The doctor removes several tiny pieces of the lining.

The laboratory cuts the tissue into thin slices and stains them. The pathologist then measures villus height and compares it with crypt depth. The pathologist also looks at the surrounding cells.

What might my report say about villous atrophy?

Reports describe the finding in a few standard ways. Each laboratory phrases it a little differently:

Villous atrophy, mild, marked, or total. The pathologist saw loss of villi and graded how much.
Marsh type. The report may give a Marsh type, such as 3a, 3b, or 3c. These types describe how much of the villi are lost.
Additional findings. The report may mention raised lymphocytes, enlarged crypts, or inflammation.
A comment about the cause. The pathologist may suggest a likely cause. The pathologist may also advise comparing the biopsy with your symptoms and blood tests. This means the biopsy alone cannot identify the cause.

Does villous atrophy mean I have celiac disease?

Villous atrophy does not always mean celiac disease. Celiac disease is a common cause, but other conditions look the same under the microscope. Doctors combine the biopsy with your symptoms and blood tests. Blood tests look for antibodies against tissue transglutaminase (anti-tTG). Most people with celiac disease have these antibodies if they are eating gluten. The celiac disease testing article explains these tests.

If blood tests are negative and a gluten-free diet does not help, doctors look for other causes. A medicine, an infection, or an immune condition may explain the change. Ask your doctor before changing your diet or stopping a medicine.

What happens after villous atrophy is identified?

The next steps depend on the cause. People with celiac disease follow a gluten-free diet, often with help from a dietitian. Doctors treat infections with appropriate medication. They review any medicine that may be to blame. They may also order stool tests, such as stool testing for parasites, or tests for tuberculosis.

The villi can recover once doctors treat or remove the cause. Your doctor may repeat the biopsy to check whether the lining has healed.

Questions to ask your doctor

What is the cause of the villous atrophy in my biopsy?
How severe is the villous atrophy: mild, marked, or total?
Does my report give a Marsh type?
Did the biopsy show other changes, such as raised lymphocytes or enlarged crypts?
Do I need celiac blood tests, and should I keep eating gluten until testing ends?
Could a medicine I take be the cause?
Do I need tests for an infection?
Will I need a repeat biopsy?
Should I see a gastroenterologist or a dietitian?