Overview
Hiatal hernia (also called hiatus hernia and paraesophageal hernia) occurs when part of the stomach protrudes into the thoracic cavity through the esophageal hiatus of the diaphragm. Embryologic development of the diaphragm is a complex process; a number of defects result in a variety of possible congenital hernias through the diaphragm. A hernia may occur through a congenitally large esophageal hiatus; however, acquired hernias through the esophageal hiatus are more common. These hiatus hernias are classified either as sliding hernias or paraesophageal hernias (see the images below). Approximately 99% of hiatal hernias are sliding, and the remaining 1% are paraesophageal.
Most hiatal hernias are found incidentally, and they are usually discovered on routine chest radiographs or computed tomography (CT) scans performed for unrelated symptoms. When symptomatic, patients may experience heartburn, dyspepsia, or epigastric pain. Rarely, the patient may present with recurrent chest infections resulting from aspiration of gastric contents. A paraesophageal or, rarely, a sliding hiatal hernia may present acutely because of a volvulus or strangulation. Paraesophageal hernias are particularly likely to incarcerate and cause symptoms of intermittent epigastric pain. Barrett esophagus is commonly associated with hiatal hernia; patients with Barrett esophagus may present with reflux symptoms or dysphagia.
Preferred examination
Plain chest radiographs may demonstrate a retrocardiac gas-filled structure. An upper GI barium series is the preferred examination in the investigation of suggested hiatal hernia and its sequelae. CT scans are useful when more precise cross-sectional anatomic localization is desired. The use of magnetic resonance imaging (MRI) and radionuclide studies is anecdotal. Ultrasonography is a sensitive means of diagnosing gastroesophageal reflux, and it is particularly attractive for use in young patients because it is noninvasive and does not require the use of ionizing radiation.
A diagram showing the 3 major orifices at the inferior aspect of the diaphragm (inferior vena cava [IVC], esophagus, aorta).
A diagram depicting a sliding hiatal hernia. The gastroesophageal junction (Jn) is located above the diaphragmatic hiatus.
This diagram of a paraesophageal hiatal hernia shows the normal infradiaphragmatic location of the gastroesophageal junction.
Although paraesophageal hernias are uncommon, they are potentially life-threatening because of the risk of volvulus and incarceration. The incidence of a hiatal hernia increases with age. When the lower esophageal sphincter is located within the thorax, its reinforcement of the diaphragmatic crus is loosened and allows gastroesophageal reflux of acid contents; such reflux may be symptomatic of hiatal hernia in one quarter of patients because of reflux esophagitis.
Krim and associates highlight the predisposing factors, mechanism, and different types of volvulus, as well as the role of imaging in making the diagnosis. Eventration of the diaphragm and hiatus hernia are precipitating factors for developing organoaxial and mesenteroaxial volvulus. The authors’ emphasize the role of imaging in making the diagnosis and distinguishing the types of volvulus to aid further management.
Limitations of techniques
The findings in an upper GI barium series may be specific, although the images may fail to demonstrate a small sliding hiatal hernia. Since gastroesophageal reflux may be intermittent, its presence may be overlooked. When no gas is present within the hernia, differentiating hernias from other retrocardiac masses may be difficult at times.
Making the diagnosis of hiatal hernia using sonography is not always straightforward, and an intermittent hernia is likely to be missed; however, some physicians regard sonography as the examination of choice in infants because the findings may differentiate duodenal causes of vomiting from esophageal causes.