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. Traditionally, these hiatus hernias were classified either as sliding hernias or paraesophageal hernias (see the images below). The anatomic classification of hiatal hernias has evolved to further differentiate paraesophageal hiatal hernias. This type 3 hiatal hernia has mixed features of both sliding and paraesophageal hernias. [1] Approximately 99% of hiatal hernias are sliding, and the remaining 1% are paraesophageal. [2, 3, 4]
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. [5, 6]
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Hiatal hernias are classified into 4 types [2] :
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Although paraesophageal hernias are uncommon, they are potentially life-threatening because of the risk of volvulus and incarceration. Symptoms include chest pain, abdominal pain, and respiratory distress. Symptomatic paraesophageal hernias require surgical repair, which is usually performed laparoscopicaly. [7]
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 25% of patients because of reflux esophagitis. [8, 9]
Krim and associates highlighted 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 hiatal 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. [10]
Imaging modalities
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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. MRI is not routinely used in the diagnosis of a hiatal hernia, and it offers no advantages over the dynamic capability of an upper GI barium series. MRI has helped to achieve a diagnosis of a paraesophageal omental hernia, in which a retrocardiac mass was shown as a fatty tumor, with contiguous blood vessels extending from the abdominal portion into the thoracic portion. Theoretically, conditions mimicking hiatal hernia on CT scans can mimic hiatal hernia on MRIs. 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. [4, 11, 12, 13, 14, 15, 16, 17, 18, 19]
Manometry studies have shown that it can be used to rule out motility disorders such as achalasia, which can mimic reflux. In some cases, high-resolution manometry provided an accurate diagnosis of hiatal hernia. [20, 21, 2]
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 ultrasonography is not always straightforward, and an intermittent hernia is likely to be missed; however, some physicians regard ultrasonography as the examination of choice in infants because the findings may differentiate duodenal causes of vomiting from esophageal causes.
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