Hiatal hernia is a condition that occurs when a portion of the stomach protrudes into the chest cavity through an opening in the diaphragm.

The diaphragm is a dome-shaped muscle used for breathing that separates the chest cavity and the abdomen. The esophagus passes through an opening in the diaphragm (called a hiatus) into the stomach. Under normal circumstances, most of the esophagus is located above the diaphragm and the stomach is located below the diaphragm. In patients with hiatal hernias, the muscle tissue around the hiatus becomes weak, causing the upper part of the stomach to bulge through the diaphragm into the chest cavity.

Hiatal hernias may also interfere with the functioning of the esophagus and stomach. Normally, the diaphragm is aligned with the lower esophageal sphincter (LES), a muscle that serves as a valve between the esophagus and stomach. When food passes through the esophagus, the LES relaxes and allows it to enter the stomach. After the food passes, the LES constricts and prevents stomach acid from flowing back into the esophagus.

Ordinarily, the diaphragm supports and puts pressure on the LES. In patients with hiatal hernias, however, the LES is located above the diaphragm. This reduces the pressure of the LES, and allows stomach acid to flow back into the esophagus.

In some patients, a hiatal hernia can cause a large part of the stomach to protrude through the diaphragm, which can exert pressure on the lungs and diaphragm. Patients with larger hiatal hernias can easily develop ulcers within the hiatal hernia (Cameron’s erosions) and especially with the use of nonsteroidal anti-inflammatory drugs (NSAIDs).

If the portion of the stomach that protrudes into the chest cavity becomes twisted, this can result in pain, vomiting and possible obstruction of the esophagus. In rare cases, the entire stomach protrudes into the chest cavity and may result in restriction of blood flow to the stomach. This is a serious condition that requires immediate surgery.

Because hiatal hernias can interfere with the functioning of the diaphragm and LES, patients have a greater of risk of developing certain conditions, including:

• Gastroesophageal reflux disease (GERD). A condition marked by the backflow (reflux) of stomach acid into the esophagus. The main symptom is heartburn.
  

  

• Erosive esophagitis. Inflammation or irritation of the esophagus, usually caused by acid reflux and often resulting in heartburn and painful swallowing.

If not treated properly, recurrent cases of GERD can lead to complications, including:

• Difficulty swallowing (dysphagia). Stomach acid can cause inflammation and scarring in the esophagus. This narrows the esophagus and makes it hard to swallow.
  
  
• Barrett's esophagus. A small number of people with chronic GERD develop Barrett’s esophagus, a precancerous condition in which the cells lining the lower part of the esophagus are changed or replaced with abnormal cells. Patients with Barrett’s esophagus are at a higher risk of developing esophageal cancer.
  
  
• Esophageal cancer. Most patients with Barrett’s esophagus do not develop cancer. However, some develop adenocarcinoma. The main symptom of an esophageal tumor is progressing difficulty with swallowing.

Hiatal hernias are common in the United States and are associated with advancing age (especially in people age 50). Women and people who are overweight are also more likely to develop hiatal hernias.