A hiatal hernia is mainly caused by a combination of weakened diaphragm muscle and increased pressure inside the abdomen, which lets part of the stomach bulge up through the opening (hiatus) in the diaphragm.

What a hiatal hernia is

  • A hiatal hernia happens when the upper part of the stomach, or nearby tissue, pushes up through the diaphragm’s natural opening where the esophagus passes.
  • Many people have small hiatal hernias without symptoms; larger ones are more likely to cause reflux or chest discomfort.

Main underlying causes

  • Age-related weakening or loss of elasticity in the diaphragm muscle, especially around the hiatus, makes it easier for the stomach to slip upward.
  • Being born with an unusually large hiatus (congenital defect) can predispose someone to a hiatal hernia even at a younger age.

Things that increase abdominal pressure

These do not always cause a hiatal hernia by themselves, but they raise the risk by repeatedly pushing the stomach upward:

  • Obesity or significant weight around the abdomen.
  • Pregnancy, which temporarily increases pressure inside the abdomen.
  • Chronic coughing (for example from COPD or smoking) or frequent heavy sneezing.
  • Straining during bowel movements because of chronic constipation.
  • Repeated heavy lifting, bending, or intense exercise that involves bearing down.
  • Forceful or repeated vomiting, which can sharply raise pressure in the upper abdomen.

Other contributing factors

  • Trauma or injury to the diaphragm area, including some types of abdominal or esophageal surgery, can weaken the structures that hold the stomach in place.
  • Genetics and family history may play a role, as some people seem more prone to develop a lax hiatus or connective-tissue weakness.
  • Older age in general is a strong risk factor; hiatal hernias are more common in middle-aged and older adults than in young people.

When to see a doctor

  • Seek urgent care for severe chest pain, trouble swallowing, vomiting, or black or bloody stools, as large or twisted hiatal hernias can occasionally cause serious complications.
  • For ongoing heartburn, regurgitation, or upper abdominal discomfort, a clinician can confirm if a hiatal hernia is present and advise on treatment such as lifestyle changes, medication, or, in some cases, surgery.