Celiac disease is an autoimmune condition where consuming gluten, a protein found in wheat, barley, and rye, triggers an immune response. This reaction leads to inflammation and damage to the lining of the small intestine in genetically predisposed individuals. Since symptoms can be vague and overlap with other digestive disorders, a definitive method is required for accurate diagnosis. An upper endoscopy, also known as an Esophagogastroduodenoscopy (EGD), is central to confirming a diagnosis of celiac disease.
How Endoscopy Facilitates Celiac Detection
The upper endoscopy procedure involves a gastroenterologist guiding a thin, flexible tube (an endoscope) equipped with a light and camera through the mouth, esophagus, and stomach to reach the small intestine. The specific target is the duodenum, the first section of the small intestine, where celiac damage is typically most pronounced. Patients fast for several hours beforehand and are usually given sedation for comfort.
While the physician may observe visual markers of damage, such as scalloping or a flattened appearance of the duodenal folds, visual inspection alone is not sufficient for diagnosis. The primary purpose of the endoscopy is to precisely collect tissue samples, a process known as a biopsy. The endoscope has tiny tools attached that allow the doctor to safely remove small pieces of the intestinal lining.
The physician takes multiple samples, generally between four to eight, from the second part of the duodenum and at least one from the duodenal bulb. Multiple samples are necessary because the intestinal damage in celiac disease can be “patchy,” meaning not all areas are equally affected.
Interpreting Biopsy Findings for Celiac Disease
The tissue samples collected are sent to a pathologist, who examines them under a microscope for structural changes indicative of celiac disease. The healthy small intestine is lined with villi, finger-like projections responsible for nutrient absorption, and grooves called crypts. In celiac disease, the immune reaction to gluten causes the villi to become blunted or flattened, a condition known as villous atrophy.
This damage is accompanied by crypt hyperplasia, an increase in the depth and size of the crypts as the body attempts to produce new cells. Pathologists also look for an increased number of immune cells, specifically intraepithelial lymphocytes, within the lining cells. A count exceeding 25 lymphocytes per 100 lining cells is considered significant.
The severity of these changes is formally graded using the Marsh classification system. This system stages the damage from Type 0 (normal) through Type 3, which is characterized by villous atrophy. Type 3 is further subdivided based on the extent of the villous flattening, with Type 3c indicating total villous atrophy. A diagnosis is confirmed when there is positive antibody serology combined with a Marsh Type 3 finding.
The Comprehensive Celiac Diagnostic Process
While the duodenal biopsy obtained via endoscopy is considered the “gold standard” for confirming celiac disease, it is not the first diagnostic step. Diagnosis typically begins with blood tests, known as serology, to screen for specific antibodies. The most common initial test measures the level of tissue transglutaminase immunoglobulin A (tTG-IgA) antibodies, which are produced in response to gluten exposure.
If serology tests are positive or highly suggestive of the condition, a confirmatory upper endoscopy and biopsy is necessary. This two-step process avoids invasive procedures for those unlikely to have the condition while ensuring the final diagnosis is accurate. The biopsy provides the physical evidence of intestinal damage required to officially confirm the diagnosis.
For both the blood test and the endoscopy to yield accurate results, the patient must be actively consuming gluten in their diet. If the patient has already started a gluten-free diet, the small intestine may heal and antibody levels can drop, leading to a false-negative result. In such cases, a doctor may recommend a controlled gluten challenge before testing to ensure the immune reaction and intestinal damage are present for detection.