A hiatus hernia is when part of the stomach protrudes through the diaphragm up into the thoracic cavity.
There are two types; sliding and rolling. Sliding hernias account for up to 95% of all hiatus hernias.
- Sliding – in this, part of stomach at the oesophageal gastric junction is pulled upwards through the diaphragm. This reduces the angle between the oesophagus and the stomach, and thus removes one of the natural anatomical barriers to reflux. However, it is unlikely that this is the sole cause for reflux, as many people have a hiatus hernia and suffer no reflux symptoms. The hernia itself never causes any symptoms – it may however contribute to reflux which will produce symptoms.
- This type of hernia is only covered by peritoneum on its lateral and anterior sides. The posterior is not covered due to the ‘bare area’ on the back of the stomach.
- Rolling (aka para-oesophageal hernia)– this is where part of the fundus of the stomach will extend through the diaphragm at a separate site to the oesophagus. They can sometimes be huge, with almost the whole stomach becoming herniated, leaving the gastro-oesophageal junction lying right alongside the pylorus.
- This type of hernia is completely surrounded by a peritoneal sac.
- Symptoms develop very rarely, and often the hernia is discovered by accident on a CXR, indicated by a fluid level behind the mediastinum. When it does cause problems, then it may cause pain (due to stomach twisting), pain and discomfort after eating, and vomiting. It may present acutely if the hernia is strangulated.
It is possible in some patients for both types of hiatus hernia to exist simultaneously. This is in fact more common than a rolling hernia on its own, and is known as a mixed hiatus hernia. In this condition, reflux is relatively common.