Villous atrophy describes the flattening or destruction of the tiny, finger-like projections, known as villi, that line the small intestine. This structural damage is a sign of intestinal injury that impairs the body’s ability to absorb nutrients. When the intestinal lining is damaged, the vast surface area dedicated to nutrient uptake is lost, leading to a condition called malabsorption. Identifying villous atrophy through a biopsy is a key step in diagnosing several gastrointestinal and autoimmune diseases.
The Structure and Function of Villi
The small intestine is responsible for absorbing most of the nutrients, fluids, and electrolytes from digested food. The inner lining is covered in millions of microscopic folds called villi. These projections are covered with even smaller microvilli, collectively forming the brush border. This intricate architecture dramatically increases the surface area for absorption.
Each villus contains a network of capillaries and a lymphatic vessel called a lacteal. Capillaries absorb simple sugars and amino acids, while lacteals primarily transport absorbed fats into the lymphatic system. This efficient system ensures that the body receives the necessary building blocks and energy from food. When villous atrophy occurs, these projections erode and shorten, transforming the highly absorptive surface into a flatter, less efficient barrier.
Primary Causes of Villous Damage
The most common cause of villous atrophy is Celiac disease, an autoimmune condition triggered by the consumption of gluten. In genetically predisposed individuals, gluten, a protein found in wheat, rye, and barley, provokes an immune response that attacks the small intestine lining. This chronic inflammation causes the destruction and flattening of the villi.
The severity of this damage is assessed using the Marsh score, a classification system based on a tissue biopsy taken during an endoscopy. This score indicates the level of villous atrophy, corresponding to the severity of intestinal damage. Diagnosis of Celiac disease relies on finding this characteristic atrophy along with specific antibody blood tests, though the biopsy remains the definitive test.
Other conditions can also lead to villous atrophy, classified as non-Celiac enteropathy. These include infections like Giardiasis, caused by a parasite, and Tropical Sprue, a chronic diarrheal illness common in tropical regions. Certain medications are also culprits, such as long-term use of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) or the blood pressure medication olmesartan.
The Consequences of Malabsorption
Villous atrophy compromises the small intestine’s ability to transfer nutrients into the bloodstream, resulting in malabsorption and systemic health issues. The specific effects depend on which nutrients are poorly absorbed, leading to a variety of deficiency syndromes.
Deficiency Symptoms
Poor absorption of essential nutrients can lead to several health problems:
- Poor absorption of iron and folate often leads to anemia, causing persistent fatigue and weakness.
- Deficiencies in fat-soluble vitamins (such as Vitamin D) and minerals (like calcium) can lead to reduced bone mineral density, increasing the risk of osteoporosis and fractures.
- In children, this lack of nutrient absorption can manifest as failure to thrive or stunted growth.
- Malabsorption can also affect neurological health, as poor Vitamin B12 and folate uptake can contribute to nerve damage and cognitive issues.
In addition to nutritional deficits, the damaged intestine cannot absorb water and electrolytes properly, resulting in common gastrointestinal symptoms. Patients frequently experience chronic diarrhea, bloating, and abdominal discomfort. The inefficiency of the digestive process can also lead to unintended weight loss and generalized malnutrition.
Restoring Intestinal Health
Treatment for villous atrophy involves identifying and eliminating the underlying cause of the damage to allow the small intestine to heal. For Celiac disease, this requires strict and lifelong adherence to a gluten-free diet, which stops the autoimmune attack on the villi. Once gluten is removed, the intestinal lining begins the process of regeneration.
The timeline for complete healing can vary significantly, often taking many months or even years for the villi to return to their normal height and function in adults. While recovery is underway, medical management focuses on correcting existing nutritional deficiencies through targeted supplementation with specific vitamins and minerals, such as iron, calcium, and B12.
When villous atrophy is caused by other factors, such as an infection or medication, treatment involves addressing the root issue. This may mean taking antibiotics to clear a parasitic infection or discontinuing the offending drug. Removing the trigger results in a faster and more complete restoration of the villous structure in these non-Celiac cases.