A hiatal hernia is not visible from the outside of your body. Unlike groin or belly button hernias that create a noticeable bulge under the skin, a hiatal hernia happens entirely inside your torso, where the upper part of your stomach pushes up through the opening in your diaphragm (the thin muscle separating your chest from your abdomen). It can only be seen through medical imaging or a camera inserted into the digestive tract.
What Happens Inside Your Body
Your diaphragm has a small opening called the esophageal hiatus, which is just wide enough for the esophagus (your food tube) to pass through on its way to the stomach. In a hiatal hernia, part of the stomach squeezes up through that opening and sits in the chest cavity, where it doesn’t belong. Picture a balloon being partially pushed through a ring: the ring is the diaphragm, and the balloon is your stomach.
What this looks like anatomically depends on the type. About 95% of hiatal hernias are the “sliding” type, where the junction between the esophagus and stomach slides upward through the opening. The entire top of the stomach migrates into the chest. In the less common paraesophageal type, the junction stays in place, but the rounded upper portion of the stomach (the fundus) bulges up beside the esophagus. Think of it as the stomach folding upward next to the food tube rather than pulling the whole connection point along with it.
There are also rarer and more complex types. A Type 3 hernia combines both patterns, with the junction and a portion of the stomach both sitting above the diaphragm. In a Type 4, other organs like the colon or spleen can herniate through the opening alongside the stomach.
What It Looks Like on a Chest X-Ray
Hiatal hernias are sometimes discovered by accident on a routine chest X-ray. The telltale sign is a gas-filled pouch sitting behind the heart. Normally, the area behind the heart contains only the esophagus and the aorta, so a round, air-containing structure in that spot stands out. Larger hernias are easier to spot this way; smaller ones can go unnoticed on a plain X-ray.
What It Looks Like on a CT Scan
CT scans provide a much more detailed picture. Radiologists look for several specific features: the thick, wavy folds of the stomach lining (called rugal folds) visible above the level of the diaphragm, soft tissue that is clearly separate from the narrow tube of the esophagus, or a lumpy, irregular contour of the digestive tract where it passes through the hiatus. In one characteristic image, a mass behind the heart may even show a fluid level inside it, confirming that a portion of the stomach, complete with its contents, has migrated upward.
CT also helps measure the size of the opening. In people without a hiatal hernia, the opening at the diaphragm typically measures about 7 to 10 millimeters across. When a hernia is present, the opening can widen to 16 to 21 millimeters or more, allowing a much larger portion of the stomach to pass through.
What It Looks Like During Endoscopy
The most direct view of a hiatal hernia comes from an endoscopy, where a thin camera is guided down the esophagus into the stomach. The doctor looks for a specific landmark: the Z-line, which is the visible color change where the pale lining of the esophagus meets the pinker, redder lining of the stomach. In a healthy anatomy, this transition sits right at the level of the diaphragm. In a sliding hiatal hernia, the Z-line is displaced more than 2 centimeters above the diaphragm.
When the camera is turned backward to look up (a “retrograde” view), the hernia appears as stomach folds extending upward alongside the scope’s shaft, creating a pouch above the diaphragm. The diaphragm itself may appear as a pinch or impression on the outside of the digestive tract.
Size matters clinically. Hernias measuring 2 centimeters or less are generally not considered significant. Larger ones, particularly those over 5 centimeters, are more likely to cause symptoms and more likely to be evaluated for potential treatment.
Tissue Changes Inside the Hernia
In larger hiatal hernias, the stomach folds that sit within the hernia sac can develop their own set of visible changes. Cameron lesions are linear erosions or shallow ulcers that form along the mucosal folds where the stomach is pinched at the diaphragm. During endoscopy, they appear as streaky, raw-looking lines on the stomach lining, sometimes with dark pigmented material overlying them. These erosions can bleed slowly over time, sometimes causing iron-deficiency anemia without any obvious digestive symptoms.
Why You Can’t See or Feel It From the Outside
Because the hernia occurs at the diaphragm, deep inside the torso and protected by the rib cage, there is no external bulge, lump, or visible change on your body’s surface. This is different from inguinal hernias (in the groin) or umbilical hernias (at the navel), which push against the abdominal wall and create a noticeable protrusion. A hiatal hernia is entirely hidden. The only external signs are the symptoms it can produce: heartburn, chest pressure, difficulty swallowing, or a feeling of fullness after small meals.