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