CLASSIFICATION AND PATHOPHYSIOLOGY
Hiatal hernias are classified into four types according to the anatomic location of the gastroesophageal junction and the extent of herniated stomach or adjacent organs.
Type I hiatal hernias, also known as sliding hiatal hernias, are defined as an upward displacement of the gastroesophageal junction into the mediastinum. In this type of hernia, the stomach maintains its longitudinal alignment and the fundus migrates beneath the esophagogastric junction. This type of hiatal hernia appears to be related to age and deterioration of the phrenoesophageal membrane due to its repetitive upward stretching during swallowing. This theory is supported by the fact that people who carry weights have a higher incidence of sliding hiatal hernia than non-weightlifting controls.
Type II and III hiatal hernias are known as paraesophageal hernias. Type II – or true paraesophageal hernia – is defined by a normally positioned intraabdominal gastroesophageal junction with an upward herniation of the stomach alongside it. The type III hiatal hernia is known as “mixed” hernia and is characterized by displacement of both the gastroesophageal junction and a large portion of the stomach into the mediastinum, which lies cephalad to the gastroesophageal junction.
These types of hernia develop when there is a defect – most of the time congenital – in the esophageal hiatus, anterior to the esophagus. A type III hernia may start as a sliding hernia or as a type II hernia. In the former case as the hiatus enlarges more fundus and body of the stomach herniates into the chest. In the latter case the gastroesophageal junction migrates cephalad over time.
Type IV hernias are characterized by an enlarged esophageal hiatus which allows the hernia sac to contain organs such as the spleen, colon or small bowel. This kind of hernias initially develop on the left anterior aspect of the esophageal hiatus. The epiphrenic fat or the anterior gastric wall serves as the leading point with the remainder of the stomach migrating into the chest over time.The laxity of the gastrocolic and gastrosplenic ligaments allows a volvulus to develop.
There are two types of volvulus:
- Organoaxial in which the greater curvature of the stomach moves anterior to the lesser curvature along the axis of the stomach.
- Mesenteriocoaxial which is less common and in which the stomach rotates along its transverse axis.
The real prevalence of hiatal hernias in the general population is not known because most patients are asymptomatic.
More than 95% of hiatal hernias are type I sliding hernias. Less than 5% are paraesophageal hernias. Of these, type III is the most common accounting for 90% of the cases, type II accounting for 3.5% to 14%, and type IV for only around 2%-5%.
Women are more prone to developing paraesophageal hernias than men. The incidence of paraesophageal hernias increases with age. There have also has been described cases of familial hiatal hernia, with autosomal dominant transmission.
Although it is thought that more than 50% of patients with paraesophageal hernias are asymptomatic, when carefully questioned, around 89% will actually report symptoms related to the hernia. Symptoms include chest pain, epigastric pain, dysphagia, postprandial fullness, heartburn, regurgitation, vomiting, weight loss, anemia and respiratory symptoms. Dysphagia and postprandial fullness are more common in paraesophageal hernias than in sliding hernias.
The most serious complication of a paraesophageal hernia is incarceration with gastric outlet obstruction and gastric strangulation, which can lead to ischemia, perforation and sepsis. The combination of chest pain, retching without vomiting and the inability to pass a nasogastric tube – the Borchard triad – is the classic diagnostic triad of incarcerated intrathoracic stomach and is a regarded as a true surgical emergency.
Bleeding or anemia are evident in one third of patients with paraesophageal hernias. It may be caused by ischemia of the gastric mucosa or by Cameron ulcers – or riding ulcers – which are linear ulcers caused by the abrasive forces created as the stomach is pinched by the diaphragmatic hiatus. These ulcers are seen during endoscopy in 5% of the patients with hiatal hernias.
Physical examination can reveal decreased breath sounds or dullness to percussion in the left chest. In type IV hernias, bowel sounds may be auscultated in the chest. The diagnosis of most of the paraesophageal hernias relies on radiographic studies and endoscopy.
- Chest X-rays usually show an opacity in the left chest and an air-fluid level behind the heart. This is usually best seen in the lateral projection.
- The CT scan shows the anatomic alterations much more accurately and can determine whether other abdominal organs have migrated into the chest.
- The barium swallow remains the easiest way to determine the location of the esophagogastric junction and thus it may help to differentiate types II and III hernias.
- Endoscopy can diagnose a paraesophageal hernia during retroflexed evaluation of the esophagogastric junction.
- In type II endoscopy will show a second orifice next to the esophagogastric junction with gastric folds extending into the opening.
- In type III a gastric pouch extending above the diaphragm with the gastroesophageal junction entering part way up the side of the pouch.
- Manometry and pH-monitoring can be difficult to interpret due to the anatomical alterations but can provide significant information on esophageal motility which can change the treatment.
The fact that paraesophageal hernia is an anatomic abnormality makes surgical restoration of the normal anatomy the only effective treatment. Patients with obstructive symptoms, bleeding or complications of gastroesophageal reflux disease associated with paraesophageal hernias should undergo surgical repair because they are the group at risk of developing life-threatening complications requiring emergency surgery. Watch and wait is the ideal strategy for patients with asymptomatic hernias.