In most cases, an endoscopy in someone with gastroparesis looks completely normal. The procedure’s main job isn’t to diagnose gastroparesis directly but to rule out physical blockages that could mimic it. When the condition is more severe, though, endoscopy can reveal telling signs: undigested food sitting in the stomach despite hours of fasting, hardened masses of food material called bezoars, or a greenish pool of bile that has refluxed back from the small intestine.
Why Endoscopy Is Part of the Workup
Gastroparesis is defined as delayed stomach emptying without a mechanical obstruction. That last part is key. Tumors, scar tissue, ulcers near the stomach’s outlet, or a narrowed pylorus (the valve between the stomach and small intestine) can all slow emptying and produce the same symptoms: nausea, vomiting, bloating, and early fullness. An upper endoscopy lets the gastroenterologist thread a thin, flexible camera down the esophagus and visually inspect the stomach lining, the pylorus, and the first part of the small intestine. If none of those structures are physically blocked or deformed, the doctor can move forward with motility testing to confirm gastroparesis.
In other words, endoscopy is less about seeing gastroparesis and more about seeing what gastroparesis is not. A structurally normal stomach on camera doesn’t mean everything is fine. It simply means the problem is functional rather than anatomical, and the next step is usually a gastric emptying study.
Retained Food After Fasting
The most recognizable endoscopic sign of gastroparesis is food still sitting in the stomach when it shouldn’t be. Before any upper endoscopy, patients are asked to fast. Standard guidelines recommend at least six hours without food, and many centers require eight hours or more since fatty foods and meat slow digestion even in healthy stomachs. After that length of fasting, a normal stomach should be mostly empty.
When the endoscopist advances the camera into the stomach and finds solid food residue, that’s a red flag for delayed gastric emptying. Clinically, finding solid food after more than six hours of fasting is considered diagnostic of delayed emptying. Gastroenterologists visually estimate the volume of retained food as small, medium, or large. A small amount might be scattered fragments clinging to the stomach walls, while a large amount can partially fill the stomach and even obscure the view, making it harder to examine the lining underneath. Retained gastric content is also defined more precisely in some centers as any amount of solid material, or fluid exceeding roughly 0.8 milliliters per kilogram of body weight collected by suction during the procedure.
It’s worth noting that retained food can also show up in people who didn’t follow fasting instructions, or in patients on certain medications that slow digestion. The finding raises suspicion for gastroparesis but doesn’t confirm it on its own.
Bezoars: Hardened Masses of Undigested Material
In more severe or long-standing gastroparesis, food that sits in the stomach for extended periods can compact into a solid mass called a bezoar. On endoscopy, bezoars appear as dense, often irregularly shaped clumps sitting in the stomach. They come in several types depending on what they’re made of.
- Phytobezoars are the most common type in gastroparesis patients. They form from indigestible plant fibers found in fruits and vegetables, especially high-fiber foods like celery, pumpkin, and grape skins. A specific subtype called a diospyrobezoar, formed from persimmons, can become particularly hard because tannins in the fruit skin act like a glue.
- Pharmacobezoars are clumps of undissolved medications. Because the stomach isn’t emptying properly, pills and capsules can accumulate and stick together rather than passing into the small intestine where they’d normally be absorbed.
Endoscopy is considered the best method for diagnosing gastric bezoars because the camera allows direct visualization and even tissue sampling if needed. In some cases, the endoscopist can treat the bezoar during the same procedure, breaking it apart with specialized tools like snares or forceps, or suctioning fragments out through a large-channel scope.
Bile Pooling and Mucosal Changes
Beyond food retention, endoscopy sometimes reveals secondary clues that the stomach isn’t moving contents along normally. One of these is the presence of bile in the stomach. Normally, bile stays in the small intestine, but when motility is disrupted, it can wash backward through the pylorus. On camera, this shows up in two ways: a “bile lake,” which is a visible pool of yellow-green fluid sitting in the stomach, and bile staining, where the stomach lining itself takes on a greenish or yellowish discoloration from prolonged bile contact.
Bile staining is considered a more reliable indicator of significant bile retention than a simple bile lake, since it suggests the bile has been sitting in the stomach long enough to mark the tissue. Over time, bile reflux can also cause visible inflammation: the stomach lining may appear red, swollen, or irritated, a condition known as bile reflux gastritis. These findings aren’t exclusive to gastroparesis and can occur for other reasons, but in the context of delayed emptying symptoms, they add to the clinical picture.
When the Endoscopy Looks Completely Normal
Many people with confirmed gastroparesis have an unremarkable endoscopy. The stomach lining looks healthy, there’s no retained food, and the pylorus opens and closes as expected. This is actually common, particularly in mild to moderate cases. The stomach’s failure to contract and push food forward is a problem of muscle coordination and nerve signaling, not one that necessarily leaves visible marks on the tissue.
This is precisely why endoscopy alone cannot diagnose gastroparesis. The gold standard test is a gastric emptying study, typically done with scintigraphy. During this test, you eat a standardized meal (often eggs or oatmeal) that contains a tiny amount of radioactive tracer, and a scanner tracks how quickly the food leaves your stomach over four hours. Retention of more than 10% of the meal at four hours confirms delayed emptying. This test quantifies the problem in a way that endoscopy simply can’t.
What the Procedure Feels Like for Gastroparesis Patients
If you have suspected gastroparesis, your prep for endoscopy may require extra attention. Standard fasting instructions call for six to eight hours without food, but because your stomach empties slowly, your doctor may ask you to follow a liquid-only diet for 24 to 48 hours before the procedure. This helps ensure the stomach is as empty as possible so the endoscopist gets a clear view of the lining. Showing up with a stomach full of food doesn’t just suggest a diagnosis; it can actually make the procedure less effective and, in rare cases, increase the risk of aspiration (food entering the airway) during sedation.
The endoscopy itself is the same as it would be for anyone else. You’ll receive sedation, the scope takes about 10 to 15 minutes, and most people go home the same day. If retained food is found, the endoscopist may suction it out during the procedure. If a bezoar is discovered, removal or fragmentation might happen right then or be scheduled as a follow-up procedure depending on the size.