Function of the Diaphragm

 

 

The diaphragm is the most important muscle used for breathing. It is a dome-shaped sheet of tissue. It consists of both muscles and tendons. The diaphragm separates the chest cavity, containing the lungs and heart, from the abdominal cavity, containing organs such as the liver, kidneys, and gastrointestinal tract.

There are three major openings which pass through the diaphragm. The aortic hiatus is the opening through which the body’s largest artery (the aorta) passes from the heart into the abdominal cavity. The second opening allows the inferior vena cava (the largest vein) to pass from the abdominal cavity up into the chest. The vena cava is firmly attached to and contiguous with the diaphragm. The third opening allows the oesophagus to pass down to the stomach. This opening (termed the oesophageal hiatus) represents a natural weak point because the muscles in this region are comparatively lax. Particularly in cases where the diaphragm is weakened, parts of the stomach (or even the entire stomach!) can pass up through this gap and migrate into the chest cavity. If this happens, we call it a hiatal hernia, i.e. a pathological (abnormal) passage of areas of the stomach into the chest cavity.

Risk Factors

A hiatal hernia (i.e. diaphragmatic hernia) is the most common type of internal hernia. It can either be congenital (i.e. present from birth) or acquired later in life. In many cases, those affected also have a weakness of their connective tissues. When combined with further risk factors, the risk of a diaphragmatic hernia occurring increases.

Beyond age (most hiatal hernias occur after the age of 50), a particular risk factor is being severely overweight (i.e. obesity). Having previous abdominal surgeries can also predispose patients to developing a hiatal hernia.

Types of Diaphragmatic Hernia

The most commonly seen hiatus hernia is termed an ‘axial-sliding’ hernia this represents about 80-90% of all hiatus hernias. In this type, the area where the oesophagus meets the stomach is shifted up the length of the oesophagus and into the chest cavity.

n much rarer cases, a paraesophageal hernia may be seen (paraesophageal = adjacent to the oesophagus). In this type of hernia, the area where the oesophagus and stomach meet remains below the diaphragm, but other parts of the stomach bunch up through the defect and end up in the chest cavity. Here they form a sack-like bulge that lies adjacent to the oesophagus on top of the diaphragm.

All other types are referred to as mixed types. In these cases, both types of issue can occur.

Key Symptom – Heartburn

A hiatus hernia does not always cause symptoms. Many hernias, especially when small, remain asymptomatic long-term, and are often only discovered by chance. This can occur, for example, on X-ray imaging of the chest and/or abdomen. These hernias do not require treatment. We are faced with a different situation when the hernia causes symptoms, and as a result significantly impacts on patients’ quality of life.

The most common clinical picture is termed gastroesophageal reflux disease (GERD), associated with severe and frequent heartburn, and often accompanied by difficulty swallowing and pain felt behind the breastbone – both symptoms tend to be worse when in a lying position. Furthermore, those affected may often suffer from a dry cough or asthma-type symptoms. Other possible symptoms which may occur include a burning sensation of the tongue, laryngitis, sleep apnoea, or even cardiac complaints – due to the heart’s ability to beat being impaired by the hernia. There has also been an increase in the worldwide incidence of oesophageal cancer – a possible consequence of a reflux disease which remains rare.

Reflux occurs when stomach acid can flow back into the oesophagus due to presence of a hiatus hernia. The lower end of the oesophagus is no longer supported by the diaphragm, allowing this reflux to occur. In healthy individuals this back-flow is prevented by a narrower area in the diaphragm (the natural oesophageal hiatus).