Abnormal endoscopy images reveal a wide catalogue of changes to the gastrointestinal lining, from subtle color shifts and altered surface textures to open ulcers, bulging masses, and swollen blood vessels on the verge of rupture. What makes endoscopy so valuable is that these visual findings often point to a specific diagnosis before a biopsy result ever comes back. A reddened, ring-shaped esophagus tells one story; a deep, punched-out stomach ulcer tells another. Understanding what endoscopists actually see on the screen, and why certain patterns raise alarms, can demystify a procedure that millions of people undergo every year.
Esophageal Findings That Signal Trouble
The esophagus is the first stretch of gut the endoscope travels through, and abnormal images here can range from mild to alarming. One of the most commonly flagged conditions is eosinophilic esophagitis, an immune-driven disorder where white blood cells pile up in the esophageal lining. On the screen it produces a distinctive set of features: stacked rings that give the esophagus a ridged, “trachealized” appearance; long vertical furrows running down the wall; white specks of exudate dotting the surface; and a pale, washed-out look caused by mucosal swelling. A validated scoring system called the EREFS grades these five major features (edema, rings, exudates, furrows, and strictures) to track disease severity and treatment response.1Digestive Diseases. Role of Advanced Diagnostics for Eosinophilic Esophagitis In severe cases the esophagus narrows so much that food gets stuck, a problem you can literally see on the image as a tight, small-caliber tube. An additional finding sometimes described as “crepe paper esophagus” refers to mucosa so fragile it tears during the exam itself.2Gut. Endoscopic assessment of the oesophageal features of eosinophilic oesophagitis: validation of a novel classification and grading system
Esophageal varices, the swollen veins that develop when liver disease backs up blood flow, present a very different picture. They appear as bluish, bulging columns running along the esophageal wall. What matters most to the endoscopist is not just the size of these veins but their surface markings. Red color signs, such as red wale markings (thin streaks on the varix surface) and hematocystic spots (small blood-filled blisters), indicate a high risk of rupture. Research has found that hematocystic spots in particular are tied to early bleeding events, even in small or straight varices.3PubMed Central. The Risk of Bleeding in Small/Straight Esophageal Varices with Red Color Sign on Endoscopy: A Retrospective Analysis from the Natural Course In other words, a varix that looks calm on the surface might be far less dangerous than a smaller one stippled with those cherry-red blisters.
When Infections Leave Their Mark on the Esophagus
Two viral infections that commonly target the esophagus in immunocompromised patients, cytomegalovirus (CMV) and herpes simplex virus (HSV), create strikingly different images. HSV esophagitis tends to produce discrete, well-bordered ulcers, sometimes with tiny blisters or a pseudomembrane coating. The ulcers may cluster together in a coalescent pattern and have raised, shouldered edges. CMV esophagitis, on the other hand, favors deep or punched-out ulcers, often with serpiginous (snake-like) outlines, an uneven base, or a yellowish exudate. CMV ulcers also tend to wrap around the esophagus more than HSV ulcers do.4PubMed Central. Can endoscopists differentiate cytomegalovirus esophagitis from herpes simplex virus esophagitis based on gross endoscopic findings? These visual differences can guide an initial clinical guess, though a biopsy is usually needed to confirm which virus is responsible.
What Stomach and Duodenal Lesions Look Like
The stomach is where endoscopy images get especially varied. One of the most common findings is gastritis linked to Helicobacter pylori, the bacterium behind most stomach ulcers and a recognized risk factor for gastric cancer. Endoscopically, H. pylori-related changes include mucosal swelling, patchy redness, small nodules, sticky mucus, enlarged folds, and the disappearance of the normal delicate vascular pattern visible in a healthy stomach. Among these features, mucosal nodularity has the highest reported diagnostic accuracy for active H. pylori infection, followed by mucosal swelling.5Clinical Endoscopy. Accuracy of Endoscopic Diagnosis of Mild Atrophic Gastritis with Helicobacter pylori Infection Other clues, like xanthomas (small yellowish patches of fat-laden cells) and intestinal metaplasia (a whitish, slightly raised change where stomach lining starts to resemble intestinal lining), can signal long-standing infection and a higher cancer risk.
When a peptic ulcer bleeds, what the endoscopist sees determines how urgently it needs to be treated. The Forrest classification, used worldwide, sorts ulcer appearances into categories based on their bleeding risk. Active spurting (Forrest IA) and active oozing (Forrest IB) are the most obvious and the most dangerous; blood is visibly flowing from the ulcer. A non-bleeding visible vessel (Forrest IIA), which looks like a small pigmented nub protruding from the ulcer base, is another high-risk finding. All three of these warrant immediate endoscopic treatment. An adherent blood clot (Forrest IIB) sitting over the ulcer crater calls for the endoscopist to remove the clot and assess what lies beneath. Lower-risk findings, such as a flat red or dark spot on the ulcer floor (Forrest IIC) or a clean, white ulcer base (Forrest III), can generally be managed without endoscopic intervention.6PubMed Central. Forrest Classification for Bleeding Peptic Ulcer: A New Look at the Old Endoscopic Classification
Early gastric cancer is one of the trickiest things to spot because it often looks subtle. Proposed criteria include a well-demarcated lesion and irregularity in color or surface pattern when viewed under standard white light. When the endoscopist switches to magnifying endoscopy with narrow-band imaging, the key warning signs become an irregular microvascular pattern or an irregular microsurface pattern, both bounded by a clear demarcation line separating abnormal from normal tissue.7PubMed Central. The endoscopic diagnosis of early gastric cancer These findings are especially important because catching cancer confined to the mucosa means it can sometimes be removed endoscopically, avoiding major surgery entirely.
Magnified Surface Patterns in the Esophagus and Stomach
Much of what separates an experienced endoscopist from a novice is the ability to read surface microarchitecture, especially under magnification with contrast agents like acetic acid. In the upper GI tract, acetic acid sprayed onto the mucosa temporarily whitens the surface and sharpens the visibility of tiny pits, grooves, and ridges. Studies using magnifying endoscopy have classified these patterns into distinct types: small round pits, ovoid or tubular pits, thin linear grooves, deep coarse grooves, finger-like villous projections, flat foveolar areas, and thick ridged patterns sometimes described as “cerebroid” because they resemble the folds on the surface of the brain.8Gastrointestinal Endoscopy. Abnormal Endoscopy Images: What Do They Show? Each pattern corresponds to a different type of epithelial lining, which in turn helps predict whether a suspicious patch is benign metaplasia, a precancerous change, or something worse. The clinical value lies in guiding biopsies: instead of sampling the stomach at random, the endoscopist targets areas where the surface pattern breaks from the surrounding norm.
Colorectal Polyps and How They Differ
Colonoscopy is probably the setting where abnormal images have the most direct impact on patient care, because removing precancerous polyps prevents colorectal cancer. The challenge is that not all polyps are precancerous. Hyperplastic polyps, which are common and almost never turn malignant, can look similar to adenomas (the kind that can become cancer) under standard white light. Narrow-band imaging makes the distinction easier by highlighting surface vessel patterns and pit architecture. Studies have shown that the criteria for telling adenomas from hyperplastic polyps using this technology can be learned in a brief training session, achieving high accuracy even among less-experienced endoscopists.9PubMed. Differentiating adenomas from hyperplastic colorectal polyps: narrow-band imaging can be learned in 20 minutes
When the endoscopist uses magnifying endoscopy in the colon, the pit pattern classification becomes critical. The system grades surface patterns from type I (normal round pits) through type V (destroyed, irregular architecture). Type V pit patterns deserve particular attention: research has found that when a type V pattern covers a bounded area of a lesion, about half of those lesions turn out to be invasive cancers that have penetrated into the deeper submucosal layer. If that pattern spreads across a wide area of the surface, extensive deep invasion should be strongly suspected.10PubMed. Diagnosis of colorectal tumorous lesions by magnifying endoscopy That distinction can change the treatment plan entirely, since a cancer confined to the superficial layers can be scooped out during the colonoscopy, while deep invasion usually requires surgical resection.
Inflammatory Bowel Disease on the Screen
Inflammatory bowel disease (IBD) produces some of the most visually dramatic endoscopy images. What the endoscopist sees also helps distinguish between the two major forms, ulcerative colitis and Crohn’s disease. Ulcerative colitis typically starts at the rectum and extends in a continuous, unbroken stretch of inflammation upstream. The mucosa looks red, swollen, and granular, often with superficial ulcerations and easy bleeding when touched. Crohn’s disease behaves differently: its inflammation is patchy and discontinuous, with normal-looking mucosa between affected segments. It often involves the area where the small intestine meets the colon, and the ulcers tend to be deeper, sometimes taking on a linear or serpiginous pattern that creates a “cobblestone” appearance of the mucosal surface.11PubMed Central. Endoscopic Diagnosis and Differentiation of Inflammatory Bowel Disease Recognizing these visual patterns early matters because the two conditions are treated differently, and misdiagnosis can lead to the wrong therapy or unnecessary surgery.
Seeing Inside the Small Bowel
The small intestine used to be the hardest part of the GI tract to examine because standard endoscopes could not reach most of it. Capsule endoscopy changed that. The patient swallows a pill-sized camera that transmits thousands of images as it travels through the gut. The most common reason for ordering one is unexplained GI bleeding after standard upper and lower endoscopy have come up empty. Capsule images commonly reveal arteriovenous malformations (tangles of abnormal blood vessels), small bowel tumors, and ulcers that were invisible to other tests.12PubMed. Imaging of small bowel disease: comparison of capsule endoscopy, standard endoscopy, barium examination, and CT The technology is good at spotting vascular and inflammatory lesions, though it has a notable blind spot: solitary tumors and other isolated lesions can be missed.13PubMed Central. Evidence-Based Guide on Capsule Endoscopy for Small Bowel Bleeding
Capsule endoscopy and standard upper endoscopy also play a role in diagnosing celiac disease. Endoscopic markers include scalloping of the duodenal folds, a mosaic pattern on the mucosal surface, loss of the normal fold architecture, nodularity, and erosions. Obtaining biopsies in patients who show these markers has been shown to increase the diagnostic yield compared with random sampling. However, the accuracy of these visual markers for predicting the underlying tissue damage is disappointing, particularly in patients with partial villous atrophy, where sensitivity ranges between roughly 50% and 78%.14PubMed Central. Role of endoscopy in the diagnosis of coeliac disease: a narrative review That means a normal-looking duodenum does not rule out celiac disease, and biopsies remain essential when clinical suspicion is high.
Vascular Lesions That Mimic Each Other
Two conditions that frequently confuse even experienced endoscopists are portal hypertensive gastropathy (PHG) and gastric antral vascular ectasia (GAVE). Both involve abnormal blood vessels in the stomach and both can cause chronic bleeding, but they arise from different mechanisms and require different treatments. PHG is driven by high pressure in the portal venous system (usually from cirrhosis) and tends to affect the body and fundus of the stomach, giving the mucosa a snakeskin-like or mosaic appearance. GAVE, sometimes called “watermelon stomach,” produces rows of flat, reddish stripes fanning out from the pylorus that look strikingly like the stripes on a watermelon rind. Direct visualization during endoscopy is often necessary to tell them apart, and in ambiguous cases a biopsy is needed.15PubMed Central. Comparison of portal hypertensive gastropathy and gastric antral vascular ectasia: an update Getting the diagnosis right matters because PHG responds to medications that lower portal pressure, while GAVE is treated with endoscopic ablation of the abnormal vessels.
Bumps Beneath the Surface
Not every abnormal finding on endoscopy involves the lining itself. Subepithelial lesions, or SELs, are masses that sit underneath the mucosa and push it upward into the lumen, creating smooth, dome-shaped bumps. They account for a small but important fraction of findings, and the differential diagnosis is broad: gastrointestinal stromal tumors (GISTs), leiomyomas, lipomas, carcinoid tumors, schwannomas, cysts, and more. The initial endoscopic evaluation considers location in the GI tract, shape, color, surface characteristics, consistency when probed, and whether the overlying mucosa is intact or ulcerated.16PubMed Central. Systematic Endoscopic Approach for Diagnosing Gastric Subepithelial Tumors
Endoscopic ultrasound (EUS) is the best tool for further characterization. By pressing an ultrasound probe against the gut wall, EUS reveals which layer of the wall the mass originates from, its internal echo pattern, its margins, and whether there are cystic spaces or abnormal lymph nodes nearby. GISTs, for example, typically appear as round or dumbbell-shaped masses that are dark (hypoechoic) on ultrasound and arise from the muscular layers. Features such as irregular borders, internal cystic areas, echogenic foci, and nearby enlarged lymph nodes raise suspicion for malignancy.17Clinical Endoscopy. Endoscopic Ultrasonography in the Diagnosis of Gastric Subepithelial Lesions European guidelines recommend EUS as the go-to investigation for SELs, while noting that EUS alone cannot definitively distinguish among all subtypes and tissue sampling may still be needed.18PubMed. Endoscopic management of subepithelial lesions including neuroendocrine neoplasms: European Society of Gastrointestinal Endoscopy (ESGE) Guideline
Radiation-Induced Changes in the Rectum
Patients who have undergone pelvic radiation therapy, commonly for prostate or cervical cancer, can develop chronic radiation proctopathy months or years later. Endoscopically, the hallmark finding is clusters of telangiectasias: tiny, dilated blood vessels scattered across the rectal mucosa that look like small red spots or patches. These fragile vessels can bleed persistently, leading to anemia over time. One counterintuitive research finding is that the affected tissue is not actually ischemic. Measurements of mucosal oxygen levels have shown that oxygenation in areas with telangiectasias is normal and even slightly higher than in unaffected areas of the rectosigmoid colon.19PubMed. Absence of ischemia in telangiectasias of chronic radiation proctopathy This matters because it suggests the bleeding comes from fragile new vessel growth rather than from tissue starved of oxygen, which has implications for how aggressively the condition is treated.
How AI and Image Enhancement Are Changing What Gets Found
Two technologies are transforming abnormal image detection. The first, narrow-band imaging (NBI), filters the endoscope’s light source down to specific blue and green wavelengths that are preferentially absorbed by hemoglobin. This makes surface blood vessels and mucosal patterns stand out in sharp contrast, turning features invisible under standard white light into clearly defined structures.20PubMed Central. Role of narrow band imaging in endoscopic submucosal dissection As described in earlier sections, NBI is now integral to distinguishing polyp types, mapping tumor margins before removal, and spotting early cancers.
The second technology is artificial intelligence. Computer-aided detection (CADe) systems, trained on hundreds of thousands of endoscopy images, can highlight potential polyps on the live video feed in real time. A large meta-analysis found that AI-assisted colonoscopy increased adenoma detection by about 20% and cut the adenoma miss rate by roughly 55% compared with standard colonoscopy.21Gastrointestinal Endoscopy. Use of artificial intelligence improves colonoscopy performance in adenoma detection: a systematic review and meta-analysis The improvement held even when only expert endoscopists were analyzed, suggesting AI finds lesions that seasoned eyes still miss. The catch is that most of the extra detections are tiny, low-risk polyps. The gain in detecting advanced adenomas, the ones most likely to become cancer, has not been significant so far.22PubMed Central. AI and Polyp Detection During Colonoscopy AI also flags more non-neoplastic polyps, meaning more tissue gets removed and sent to pathology even when it would never have caused harm.23Scientific Reports. Clinical evaluation of a real-time artificial intelligence-based polyp detection system: a US multi-center pilot study
Perforations and Other Procedure-Related Findings
Sometimes the abnormal image is created by the procedure itself. Therapeutic endoscopy, which includes removing polyps, dilating strictures, and dissecting tumors from the gut wall, carries a small risk of perforation. On the screen, a perforation may look like a visible hole through which the endoscopist can see peritoneal fat or the outer surface of the bowel. In other cases, the clue is more subtle: a suspicious defect in the wall, a pocket of air where it should not be, or a site where tissue suddenly looks thinner than expected. Early recognition of such a defect during the procedure is the single most important factor in determining whether endoscopic closure will succeed and the patient will do well.24PubMed Central. Endoscopic management of perforations, leaks and fistulas Clips, suturing devices, and stents can often seal a perforation on the spot, but only if the endoscopist recognizes what they are looking at before the scope is withdrawn.
Artifacts That Fool the Eye and the Algorithm
Even with advanced optics and AI, endoscopy images are not always what they seem. Artifacts, visual distortions introduced by the equipment or the environment inside the gut, can obscure genuine pathology or mimic it. Common culprits include specular reflections (bright glare spots from the light source bouncing off a wet mucosal surface), air bubbles, blurring from rapid scope movement, saturation from overexposed lighting, and the presence of blood or instruments in the field of view. Researchers have begun training deep-learning models to automatically identify and flag these artifacts in real time so that the endoscopist or the AI polyp-detector can account for them rather than being misled.25PubMed Central. Endoscopy Artefact Detection by Deep Transfer Learning of Baseline Models The practical concern is real: a bubble sitting on a flat polyp can hide it entirely, while a glare spot on normal mucosa can look like a raised lesion. As AI systems become standard, their ability to ignore artifacts and focus on genuine tissue abnormalities will be just as important as their ability to spot polyps in the first place.