Celiac disease can sometimes be spotted during a standard upper endoscopy, but the visual signs are unreliable enough that biopsies remain essential. An experienced gastroenterologist may notice telltale changes in the lining of the duodenum, such as scalloped folds, a mosaic-like pattern, or flattened villi, yet roughly half of people with confirmed celiac disease have a duodenum that looks only mildly abnormal or completely normal to the naked eye. That gap between what the endoscopist sees and what the tissue reveals under a microscope is the central tension in celiac diagnosis, and it shapes everything from biopsy protocols to newer imaging technologies designed to close the gap.
What Endoscopic Markers Actually Look Like
During an upper endoscopy, the scope passes through the esophagus and stomach before reaching the duodenum, the first stretch of the small intestine and the area most affected by celiac disease. In a healthy duodenum, the mucosal folds (sometimes called Kerckring’s folds) are tall and evenly spaced, and the surface has a velvety texture created by millions of tiny finger-like projections called villi. When celiac disease damages that lining, several changes become visible.
The most commonly described markers include scalloping of the duodenal folds, a mosaic or “cracked mud” pattern on the mucosal surface, a reduction in the number or complete loss of folds, fissuring, nodularity, and visible blood vessels showing through thinned-out tissue.1PubMed Central. Role of endoscopy in the diagnosis of coeliac disease: a narrative review One early study found that loss or reduction of those folds was the single most reliable visual clue, with a sensitivity of about 76% and a specificity of 98% for celiac disease when present.2PubMed. Value of endoscopic markers in celiac disease The same study reported that when all endoscopic markers were considered together, they had a sensitivity of 94% and a specificity of 92%. Those numbers sound reassuring, but they came from a population of patients already suspected of having celiac disease, which inflates the apparent accuracy.
How Often the Duodenum Looks Normal
The encouraging sensitivity figures from earlier studies have not held up uniformly in broader practice. A study examining routine endoscopies found that the duodenal mucosa appeared definitely atrophic in only about half of patients who turned out to have celiac disease. Another third showed only mild abnormalities, and about one in seven looked completely normal.3PubMed Central. Coeliac Patients Are Undiagnosed at Routine Upper Endoscopy This means that if an endoscopist relied solely on what the duodenum looked like, a substantial number of celiac patients would be missed.
The explanation is partly about disease severity. Endoscopic markers tend to be absent in milder forms of celiac damage and in cases where the damage is patchy rather than widespread. When the intestinal changes are limited to early-stage inflammation without significant villous flattening, the mucosa can appear grossly normal.4PubMed Central. Diagnostic yield of endoscopic markers for celiac disease For that reason, a duodenum that looks fine during the procedure does not rule celiac disease out, and biopsies should still be taken whenever clinical suspicion exists.
Why Multiple Biopsies Are Taken
The American College of Gastroenterology recommends that when celiac disease is suspected, at least four biopsy samples be taken from the distal (farther) part of the duodenum and one or two from the duodenal bulb, the very beginning of the duodenum just beyond the stomach.5PubMed Central. Efficacy of duodenal bulb biopsy for diagnosis of celiac disease: a systematic review and meta-analysis That might sound like a lot, but it comes down to a quirk of the disease: celiac damage is not always evenly distributed.
Villous atrophy can be patchy, meaning one spot in the duodenum may show severe damage while a spot a few millimeters away looks perfectly healthy. In one study of patients with positive celiac antibodies, about one in five had patchy villous atrophy. Taking at least three biopsies, including one from the duodenal bulb, caught all cases. But identifying the most severe degree of damage required five biopsies.6PubMed. Patchy villous atrophy in adult patients with suspected gluten-sensitive enteropathy: is a multiple duodenal biopsy strategy appropriate? Current guidelines from both the ACG and the British Society of Gastroenterology now recommend a minimum of five biopsy specimens to maximize diagnostic accuracy and reduce the chance that a patchy lesion is missed.7Journal of Translational Gastroenterology. Pitfalls in the Diagnosis of Celiac Disease: Bridging Gaps from Serology to Clinical Practice
The biopsies are tiny, usually about the size of a pinhead, and are painless because the small intestine doesn’t have pain-sensing nerves in the way your skin does. The tissue samples are then examined under a microscope, where a pathologist looks for the hallmarks of celiac damage: flattened or blunted villi, deepened crypts (the grooves between the villi), and an increase in certain immune cells within the epithelial layer.8American Journal of Gastroenterology. Morphometric Evaluation of Duodenal Biopsies in Celiac Disease
When You Might Skip the Biopsy
For children, the landscape is different. Pediatric guidelines now allow celiac disease to be diagnosed without a biopsy in certain circumstances. If a symptomatic child has blood antibody levels (specifically IgA tissue transglutaminase) at ten or more times the upper limit of normal and a confirmatory endomysial antibody test is also positive, the diagnosis can be made on blood work alone.9Gastroenterology. Accuracy of the No-Biopsy Approach for the Diagnosis of Celiac Disease in Adults: A Systematic Review and Meta-Analysis The 2023 ACG guidelines endorse this approach for pediatric patients, noting that antibody levels at that threshold have a positive predictive value of 99% for celiac disease in children.10PubMed. Path Towards Biopsy-Free Diagnosis of Celiac Disease in Pediatric Patients
For adults, the situation is less settled. While research into a no-biopsy strategy for adults is active, current adult guidelines still consider small-bowel biopsy a critical part of the diagnostic workup.11PubMed Central. Non-biopsy Strategy for the Diagnosis of Celiac Disease in Adults: A Narrative Review The caution is reasonable. Adults more commonly have atypical presentations, other conditions that mimic celiac histology, and a wider range of differential diagnoses that a biopsy helps sort out.
Advanced Imaging That Bridges the Gap
Standard white-light endoscopy, the default mode that illuminates the gut in ordinary visible light, is what most people experience during the procedure. But newer imaging modes are making it easier to detect villous atrophy without waiting for biopsy results.
Narrow-band imaging (NBI) uses filtered light at specific blue and green wavelengths to enhance the surface texture and vascular patterns of the mucosa. A meta-analysis of six studies found that NBI detected villous atrophy with about 93% sensitivity and 95% specificity.12PubMed. Narrow-band imaging for optical diagnosis of duodenal villous atrophy in patients with suspected coeliac disease: A systematic review and meta-analysis A near-focus version of NBI has been developed into a formal classification system for villous architecture that shows substantially better agreement between observers than standard white-light endoscopy.13PubMed. Near-focus narrow-band imaging classification of villous atrophy in suspected celiac disease: development and international validation A combined approach pairing NBI with a water immersion technique, where the duodenum is filled with water to create a clearer optical window, has also shown a strong correlation with villous atrophy on biopsy.14PubMed. Narrow band imaging combined with water immersion technique in the diagnosis of celiac disease
These technologies don’t replace biopsy yet, but they give the endoscopist real-time information that can guide where to sample. If NBI highlights a patch of abnormal-looking mucosa that white light missed, a targeted biopsy from that exact spot is more likely to capture the damage. In the context of patchy disease, that targeted approach is genuinely useful.
Artificial Intelligence at the Scope
One of the more promising developments is the use of AI algorithms trained on thousands of endoscopic images to flag villous atrophy during the procedure. In one study, an AI system outperformed both endoscopy fellows and experienced experts at detecting villous atrophy on still images. When used as a decision-support tool alongside non-expert endoscopists, the AI significantly improved their detection accuracy, with a particularly notable effect on difficult-to-read images.15PubMed. Detection of duodenal villous atrophy on endoscopic images using a deep learning algorithm
This kind of tool could be especially valuable in settings where celiac disease isn’t the primary reason for the endoscopy. Many celiac diagnoses are made incidentally, when a patient undergoing endoscopy for acid reflux or other complaints happens to have a duodenum that looks abnormal. An AI running in the background could prompt the endoscopist to take biopsies they might not have otherwise considered. Routine biopsies during endoscopies performed for gastroesophageal reflux have been shown to catch celiac cases, but the cost-effectiveness depends heavily on the prevalence of undiagnosed celiac disease in the patient population being scoped.16PubMed Central. Cost Effectiveness of Routine Duodenal Biopsy Analysis for Celiac Disease During Endoscopy for Gastroesophageal Reflux
How Blood Tests and Biopsy Results Relate
You might wonder whether high antibody levels on a blood test predict what the biopsy will show. They do, to a degree. Higher levels of IgA anti-tissue transglutaminase antibodies tend to correlate with more severe mucosal damage. In one study, about 82% of patients with the most advanced histological damage had high antibody titers, and titers above a certain threshold had a positive predictive value of roughly 78% for severe villous atrophy.17PubMed Central. Association of Tissue Transglutaminase Antibody Titer with Duodenal Histological Changes in Children with Celiac Disease Another study confirmed that antibody ratios above a defined cutoff could identify significant mucosal damage with high specificity.18PubMed. Correlation between IgA tissue transglutaminase antibody ratio and histological finding in celiac disease
But the correlation is far from perfect, especially at lower antibody levels. Some people with modestly elevated serology still have significant damage on biopsy, and some with very high antibody levels have relatively preserved villi. That imperfect overlap is a big part of why adults are still sent for endoscopy rather than diagnosed on blood tests alone.
Potential Celiac Disease and the Normal-Looking Biopsy
A frustrating scenario for both patients and doctors occurs when someone has positive celiac antibodies and the right genetic markers but a biopsy that comes back essentially normal. This is known as potential celiac disease. The small intestinal mucosa in these patients falls into the mildest end of the damage spectrum, sometimes showing only a subtle increase in intraepithelial immune cells or deposits of IgA antibodies detectable only with specialized staining.19PubMed Central. The Challenge of Treatment in Potential Celiac Disease
Potential celiac disease is not a false alarm. Studies tracking children with positive antibodies and initially normal biopsies have shown that a significant proportion eventually develop full-blown mucosal damage over time.20PubMed. Natural history of potential celiac disease in children Whether these patients should start a gluten-free diet immediately or wait for follow-up biopsies remains a matter of debate. But the takeaway for anyone reading their own results is that a “normal” endoscopy and biopsy do not necessarily close the book on celiac disease when serology is clearly positive.
Other Conditions That Look Similar on Endoscopy
Villous atrophy is the hallmark of celiac disease under the microscope, but it is not exclusive to it. Other conditions can produce a similar appearance, including certain infections, medication reactions (particularly from the immunosuppressant olmesartan and other drugs), autoimmune enteropathies, tropical sprue, Crohn’s disease affecting the duodenum, and common variable immunodeficiency.21PubMed. Noncoeliac enteropathy: the differential diagnosis of villous atrophy in contemporary clinical practice The visual appearance during endoscopy does not distinguish celiac disease from these mimics. That is why the diagnosis rests on the combination of serology, biopsy findings, clinical history, and sometimes genetic testing, rather than any single piece of the puzzle.
A large international study of patients diagnosed with celiac disease also found that the endoscopy picked up other incidental findings in about 10% of patients, most commonly erosive reflux esophagitis and gastric erosions. Older patients (over 50) were nearly twice as likely as younger patients to have at least one additional abnormality discovered during the procedure.22PubMed Central. Upper gastrointestinal endoscopic findings in celiac disease at diagnosis: A multicenter international retrospective study So beyond its role in diagnosing celiac disease, the endoscopy serves a useful screening function for other upper GI problems that might be contributing to symptoms.
Monitoring on a Gluten-Free Diet
After diagnosis, some patients undergo follow-up endoscopies to check whether the intestinal lining has healed on a gluten-free diet. Mucosal recovery is a good sign that the diet is working and that long-term complications are less likely. Research has explored whether advanced endoscopic techniques could eventually eliminate the need for repeat biopsies during monitoring. One study using a water immersion technique found it could predict histological recovery of the villi with high accuracy, suggesting that an endoscopy-based visual approach might one day serve as a less invasive monitoring tool.23PubMed. A highly accurate method for monitoring histological recovery in patients with celiac disease on a gluten-free diet using an endoscopic approach that avoids the need for biopsy
For patients with refractory celiac disease, where symptoms and intestinal damage persist despite strict gluten avoidance, capsule endoscopy has a role. A small, swallowable camera captures images along the entire small intestine, reaching areas that a standard upper endoscopy cannot. This is useful for spotting complications like ulcerative jejunitis or, in rare cases, intestinal lymphoma, which are serious risks in the refractory form of the disease.24PubMed Central. Capsule endoscopy in celiac disease
What an Endoscopy Actually Tells You in Practice
If you are scheduled for an endoscopy and celiac disease is on the table, here is what to realistically expect. The procedure itself typically takes ten to fifteen minutes. You will be sedated, so you won’t feel the biopsies being taken. Afterward, the endoscopist may mention whether the duodenum looked normal or suspicious, but that impression is just a preliminary read. The definitive answer comes from the pathology report, usually a few days to a couple of weeks later.
One critical point that trips people up: you should not start a gluten-free diet before the endoscopy unless your doctor specifically tells you to. Removing gluten can allow the intestinal lining to start healing, which reduces both the visual markers and the biopsy findings, potentially leading to a false-negative result. The same principle applies to the blood tests. Both serology and histology are most informative when you are actively eating gluten.
If your biopsy comes back with damage graded at the more severe end of the spectrum, the diagnosis is usually straightforward when combined with positive serology. If it comes back with only mild changes or looks normal, and your blood work is positive, the picture gets murkier and may require additional testing, genetic analysis, or follow-up over time. Celiac disease is a diagnosis that sometimes unfolds over months rather than resolving in a single visit, and a normal-appearing endoscopy is one reason that can happen.