A hiatal hernia is herniation of the stomach into the thorax through the hiatus. Hiatal hernias are divided into four types:

• type 1: sliding hiatal hernia (~95%)
• type 2: paraesophageal hiatal hernia with the gastroesophageal junction in a normal position
• type 3: mixed or compound type, paraesophageal hiatal hernia with displaced gastroesophageal junction
• type 4: mixed or compound type hiatal hernia with additional herniation of viscera