A small intestine biopsy is widely considered a primary method for confirming a celiac disease diagnosis. This procedure directly examines the lining of the small intestine for specific changes characteristic of the condition. The insights gained from a biopsy provide direct evidence of intestinal damage, which is a hallmark of this autoimmune disorder.
The Endoscopic Biopsy Procedure
The biopsy for celiac disease is typically performed during an upper endoscopy, also known as an esophagogastroduodenoscopy (EGD). During this outpatient procedure, patients usually receive a sedative to help them relax, and a local anesthetic may be applied to numb the throat. A thin, flexible tube equipped with a light and camera, called an endoscope, is gently guided through the mouth, down the esophagus, and into the stomach before reaching the first part of the small intestine, known as the duodenum.
The gastroenterologist uses tiny tools passed through the endoscope to collect several small tissue samples from the duodenal lining. It is common practice to take at least four to six samples, typically from both the duodenal bulb and the second part of the duodenum, to ensure a comprehensive assessment. Patients generally do not feel pain when the samples are taken, as the lining of the small intestine does not have nerve endings. The entire procedure usually takes less than 30 minutes.
Analyzing the Biopsy Sample
After collection, the tissue samples are sent to a pathology laboratory for microscopic examination. Pathologists specifically look for characteristic changes in the small intestine’s lining. A healthy small intestine is lined with numerous tiny, finger-like projections called villi, which increase the surface area for nutrient absorption, similar to a plush, shaggy carpet.
In individuals with celiac disease who are consuming gluten, the immune system reacts, causing inflammation and damage to these villi. This damage leads to their flattening and shortening, a condition known as villous atrophy, which can be likened to a worn, flat carpet. Pathologists often use a grading system, such as the Marsh classification, to describe the severity of this intestinal damage. Marsh classifications range from Marsh 0 (normal) to Marsh 3 (indicating varying degrees of villous atrophy, from partial to total flattening), with increased intraepithelial lymphocytes and crypt hyperplasia also being considered.
Factors Influencing Biopsy Accuracy
When performed under appropriate conditions, a small intestine biopsy offers reliable insights into the presence of celiac disease. However, certain factors can affect its accuracy, particularly leading to a false negative result where damage is present but not detected.
One significant factor is the patient’s diet leading up to the procedure. For the characteristic intestinal damage to be apparent, the individual must be consuming gluten regularly for several weeks before the biopsy, often recommended as daily gluten intake for at least six to eight weeks. If someone has already adopted a gluten-free diet before testing, the intestinal lining can begin to heal, masking the damage and potentially leading to an inaccurate result. In such cases, a “gluten challenge” may be recommended, where gluten is reintroduced into the diet, typically 3 to 10 grams per day, for a specific period before the biopsy.
Additionally, celiac-related intestinal damage can be patchy, meaning it may not be uniformly distributed throughout the small intestine. The expertise of the pathologist examining the samples and proper handling, including correct orientation of the tissue, also influence accuracy.
Interpreting Results with Other Diagnostic Tools
A celiac disease diagnosis is rarely based solely on a biopsy; rather, it typically involves a comprehensive evaluation that includes other diagnostic tools. Celiac blood tests, also known as serology, are usually the initial screening step. These tests look for specific antibodies, such as tissue transglutaminase IgA (tTG-IgA) and endomysial IgA (EMA-IgA), which the body produces in response to gluten in individuals with celiac disease.
A positive blood test result, particularly a high tTG-IgA level, often prompts the recommendation for a biopsy to confirm the diagnosis. When both blood tests are positive and the biopsy shows characteristic intestinal damage, it strongly supports a celiac disease diagnosis. If blood tests are positive but the biopsy is negative, this might suggest potential celiac disease or indicate that the patient was not consuming enough gluten before the biopsy, which can lead to a false negative result. In some instances, for children and certain adults with very high tTG-IgA levels, a diagnosis might be made without a biopsy, though this approach is not universally adopted for all adult cases and requires careful consideration.