Small bowel -
This article was last reviewed and updated on April 26, 2018.
by Shaheed Hakim, MD FRCPC
Celiac disease is a condition that develops in people who have a genetic sensitivity to gluten.
Gluten causes the immune system to damage the cells that line the inside of the small bowel.
The damaged small bowel cannot absorb nutrients which can lead to weight loss and diarrhea.
When examined under a microscope, the tissue from the small bowel will a loss of villi and increased lymphocytes.
The small intestine is a part of your gastrointestinal tract. Food travels into the small intestine from the stomach. Another name for the small intestine is the small bowel. The small intestine is responsible for absorbing nutrients from the food that we eat after the food is broken down in the stomach.
The inner surface of the small intestine is lined by epithelial cells that form structures called glands. This surface contains many small folds that form millions of finger like projections called villi. These folds greatly increase the surface area available for food absorption.
Some people are born with an inability to properly absorb gluten. This is known as gluten sensitive enteropathy, or Celiac disease.
Gluten can be found in grains such as wheat, rye and barley. In those with impaired absorption, gluten acts as an irritant to the epithelium of the small intestine. This irritation causes small immune cells called lymphocytes to enter the space between the epithelial cells in the epithelium. Pathologists refer to this as increased intraepithelial lymphocytes.
Overtime, these immune cells damage the epithelium which causes a loss of the normal villi. Pathologists describe this change as atrophy or blunting of the villi.
A biopsy is usually performed because the patient has symptoms suggestive of Celiac disease (gluten sensitive enteropathy), which may include weakness and diarrhea. These symptoms occur when the patient eats food that contain gluten. Biopsies are usually taken from the 2nd part of the duodenum, where the changes associated with Celiac disease are easiest to recognize.
A diagnosis of Celiac disease (gluten sensitive enteropathy) requires both clinical (serology) and pathological (biopsy) confirmation.
Your pathologist can confirm the diagnosis when they see increased intraepithelial lymphocytes in the epithelium of the small intestine, as well as the abnormal blunting or atrophy of the villi. This blunting can further be graded as mild, moderate or severe. In severe blunting there are no villi seen and the epithelium looks flat.
Increased intraepithelial lymphocytes with no/mild villous blunting
When a biopsy is performed in the early stages of the disease, the small intestine may show only mild changes including an increased number of lymphocytes in the epithelium on the inner surface of the tissue. In many early cases, the villi are still normal and the report will refer to this as 'no or mild villous blunting'.
The finding of increased intraepithelial lymphocytes without villous blunting is not unique to Celiac disease and may be seen in other conditions. For example, Helicobacter gastroenteritis, medications (ie. Olmesartan), tropical sprue, protein intolerance, bacterial overgrowth and viral gastroenteritis all cause changes that look similar under the microscope. Your pathologist will likely mention some of these conditions in the comment section.
The earliest change is referred to as ‘low-grade’ dysplasia. The cells in low grade dysplasia are abnormal but are still non-cancerous (benign). In some cases, the cells become even more abnormal and progress to ‘high-grade’ dysplasia. These cells look very similar to cancer cells, however, they are still only seen in the epithelium on the inner surface of the stomach.
High grade dysplasia is considered a precursor because some cases will turn into cancer (a malignant tumour) over time. Your pathologist will closely examine the tissue for any evidence of dysplasia and will describe it in your report if it is seen.
Enteropathy-associated T-cell lymphoma (EATL)
In some patients, a gluten free diet is not enough to prevent inflammation and damage in the small intestine. These patients are classified as having refractory celiac disease. In a specific type of refractory celiac disease, the inflammatory cells (intraepithelial lymphocytes) divide and multiply in an abnormal pattern. This leads to a cancer called enteropathy-associated T-cell lymphoma (EATL), a type of lymphoma.