Hiatal hernias are common anatomical changes often associated with persistent symptoms like heartburn and regurgitation. These symptoms frequently lead patients to undergo an upper endoscopy, also known as esophagogastroduodenoscopy (EGD). While endoscopy is a standard procedure for evaluating the upper digestive tract, a negative result does not always rule out the presence of a hiatal hernia. Understanding the limitations of this procedure is important for individuals who continue to experience discomfort. For this reason, it is possible for a hiatal hernia to go undetected during a routine endoscopic examination.
Defining the Hiatal Hernia and Endoscopic Detection
A hiatal hernia occurs when the upper part of the stomach pushes upward through the hiatus, the opening in the diaphragm. The diaphragm is a dome-shaped muscle separating the chest and abdomen. This upward movement displaces the normal anatomical relationship between the esophagus and the stomach, which can compromise the function of the lower esophageal sphincter and allow acid reflux.
An upper endoscopy involves inserting a flexible tube with a camera to visualize the lining of the esophagus, stomach, and duodenum. To identify a hiatal hernia, the endoscopist focuses on two specific landmarks. The first is the Z-line, which marks the squamocolumnar junction where the esophageal and gastric linings meet. The second is the diaphragmatic pinch, the point where the diaphragm muscle constricts the esophagus.
In a healthy individual, the Z-line and the diaphragmatic pinch should be located in close proximity, separated by less than two centimeters. A hiatal hernia is diagnosed when the Z-line and a portion of the stomach have moved more than two centimeters above the diaphragmatic pinch. This distance between these two points is the primary measurement used for endoscopic identification.
Why Endoscopy May Fail to Identify the Hernia
The most frequent cause for a missed diagnosis relates to the nature of the most common type, known as a sliding hernia (Type I). These hernias are not fixed in place and move dynamically between the chest and abdominal cavities. The hernia may only be present when intra-abdominal pressure increases, such as during coughing or straining. When the patient is relaxed and lying supine during the procedure, the stomach can easily slide back down.
The supine position, along with the sedation often administered, reduces the pressure gradient across the diaphragm. This physiological change allows the herniated portion of the stomach to temporarily return to its normal position below the diaphragm. This temporary reduction effectively masks the anatomical defect, causing the procedure to show a normal relationship between the Z-line and the diaphragmatic pinch.
Very small hiatal hernias, particularly those less than two centimeters, pose a technical challenge for differentiation from normal anatomy. The visual distinction between a small hernia and the natural laxity of the gastroesophageal junction can be subtle. The endoscopist must rely on precise measurement and careful observation, which can be complicated by slight movements.
The diagnosis relies on the subjective assessment and measurement skills of the individual endoscopist. Studies show inter-observer variability in accurately measuring the distance between the Z-line and the diaphragmatic pinch. This subjectivity means that what one practitioner classifies as a small hernia, another might interpret as normal anatomical laxity, contributing to the potential for a miss.
The endoscopy procedure requires the inflation of air into the stomach to distend the organ and provide a clear view of the mucosal lining. This necessary insufflation of air can contribute to the hernia being missed, as the increased pressure can physically push a small, sliding hernia back into the abdominal cavity.
The technique used by the practitioner also plays a part in detection success. The standard technique involves retroflexion, where the endoscope tip is bent back 180 degrees to view the junction from inside the stomach looking up. If the practitioner omits this maneuver or does not carefully observe the junction during scope withdrawal, a small or transient hernia is more likely to be overlooked.
Other Tools for Confirming a Hiatal Hernia
When clinical suspicion remains high despite a negative endoscopy, alternative imaging methods are utilized to confirm the diagnosis. The Barium Swallow, or Upper Gastrointestinal (GI) Series, is frequently employed because it offers a dynamic assessment of the upper digestive tract. The patient drinks a contrast agent, and the movement of the esophagus and stomach is tracked using real-time X-ray imaging.
This method is often superior to endoscopy for visualizing sliding hiatal hernias because the patient is imaged in various positions, including standing or lying down. Imaging the patient upright and while actively swallowing allows the practitioner to observe anatomical changes under physiological stress. This dynamic imaging can capture the transient upward movement of the stomach that endoscopy missed.
High-Resolution Manometry (HRM) assesses the function and pressure profile of the esophagus and its sphincters. While primarily used for motility disorders, HRM can indirectly confirm a hiatal hernia by precisely mapping the location of the lower esophageal sphincter (LES) relative to the diaphragmatic pinch. A separation of more than one centimeter between the LES pressure zone and the crural diaphragm pressure zone suggests a hiatal hernia.
Computed Tomography (CT) scans are not the first-line diagnostic for smaller hiatal hernias but are useful in specific scenarios. CT imaging provides detailed cross-sectional views that can identify the size and contents of larger hernias, particularly complex paraesophageal hernias. This imaging is relevant if complications are suspected, such as twisting, obstruction, or strangulation of the herniated stomach portion.
Ambulatory pH monitoring or impedance-pH monitoring provides functional confirmation of a hiatal hernia’s effect. This test measures the frequency and duration of acid or non-acid reflux episodes in the esophagus over a 24 to 48-hour period. Persistent, abnormal reflux confirmed by this monitoring, even with a negative endoscopy, suggests an underlying anatomical issue is still present.
When to Seek Further Evaluation
A patient who receives a negative endoscopy result but continues to suffer from persistent, classic symptoms should seek further evaluation. Ongoing symptoms like frequent heartburn, acidic regurgitation, chronic cough, or unexplained chest discomfort warrant a follow-up conversation with the gastroenterologist. These symptoms indicate that an underlying anatomical or functional issue may still be present.
The next step involves a detailed review of the symptoms and a discussion about the possibility of a missed diagnosis. Patients should request alternative diagnostic testing, such as a Barium Swallow or High-Resolution Manometry, to gain a more complete picture. Pursuing further evaluation ensures that the correct cause of the discomfort is identified and appropriately managed.