A hiatal hernia (HH) occurs when the upper part of the stomach pushes upward into the chest cavity through the esophageal hiatus, a small opening in the diaphragm. While many people experience no symptoms, others may have chronic heartburn or reflux. When a diagnosis is necessary, imaging tests are required. A routine Computed Tomography (CT) scan is often insufficient for initial diagnosis and can easily miss a hiatal hernia, necessitating more specialized testing.
Understanding the Hiatal Hernia
A hiatal hernia involves the diaphragm, the muscle separating the chest from the abdomen. The esophagus passes through a natural opening in this muscle, the hiatus, before connecting to the stomach. When the surrounding muscle tissue weakens, a portion of the stomach can bulge through this opening.
The condition is categorized into two types, which differ in their anatomical presentation. The sliding hiatal hernia, or Type I, is the most common, occurring when the junction between the esophagus and stomach slides up into the chest. This type is frequently associated with gastroesophageal reflux disease (GERD).
The second major category is the paraesophageal hernia. Here, a part of the stomach pushes up alongside the esophagus while the junction remains in its normal position. Although less common, the paraesophageal type is more serious because it carries a higher risk of complications, such as the stomach becoming twisted or having its blood supply cut off.
CT Scan Performance: Why Detection Can Be Difficult
A CT scan is a static, cross-sectional imaging tool that excels at visualizing solid organs, bone, and acute emergencies. However, it is not optimal as the primary screening method for a hiatal hernia due to the condition’s dynamic nature. Small hernias, particularly the sliding type, often move or reduce in size depending on the patient’s breathing or position, making them transiently visible.
Since the CT scan is performed with the patient lying flat and holding their breath, it may capture the stomach when it has slid back down into the abdomen, resulting in a false-negative finding. The small size of the most common sliding hernias also makes them subtle, easily blending into the surrounding soft tissue on a two-dimensional image. These subtle changes are hard to distinguish without specialized preparation.
Furthermore, CT scans are often performed without the necessary contrast agents that specifically outline the gastrointestinal (GI) tract. While oral contrast can improve visualization by filling the stomach, many routine CT scans lack this preparation. Without a clear delineation of the stomach’s inner lining, it is difficult to confidently identify a small protrusion above the diaphragm.
The strength of the CT scan is for assessing complications, not initial diagnosis. It is the preferred method when severe issues like strangulation, obstruction, or perforation are suspected. The CT can clearly show the status of the blood vessels and surrounding structures in these cases.
Definitive Diagnostic Imaging
The gold standard imaging test for definitive diagnosis is the barium swallow, also known as an Upper GI Series or esophagram. This test involves the patient swallowing a liquid barium mixture that coats the esophagus and stomach. This coating makes the structures visible on a series of X-ray images.
The primary advantage of the barium swallow is its ability to provide functional and anatomical information. The radiologist can observe the flow of the contrast and the movement of the stomach in real-time. This dynamic visualization is far more effective at capturing a sliding hernia than a static CT image.
Another highly effective diagnostic procedure is an esophagogastroduodenoscopy (EGD), commonly called an upper endoscopy. During this procedure, a flexible tube with a camera is passed down the throat to directly visualize the esophagus and stomach. The physician can directly see the gastroesophageal junction and measure the size of the hiatal hernia with high accuracy. The endoscopy is also invaluable for checking for associated complications, such as inflammation or tissue changes like Barrett’s esophagus.