A hiatal (or hiatus) hernia is the abnormal protrusion of any abdominal structure/organ, most often a portion of the stomach, into the thoracic cavity through a lax diaphragmatic esophageal hiatus. It may be congenital or secondary to ageing, obesity, and/or smoking. There are four types of hiatal hernia: sliding, paraesophageal, mixed, and complex. Sliding hiatal hernias, where the gastroesophageal junction (GEJ) and the gastric cardia migrate into the thorax, account for 95% of hiatal hernias. In paraesophageal hernias (PEH), only the gastric fundus herniates into the thorax, whereas in mixed hiatal hernias, the GEJ as well as the gastric fundus herniate. Complex hiatal hernias are rare and characterized by protrusion of any abdominal organ other than the stomach. Nearly half of all patients with hiatal hernia are asymptomatic and require no medical or surgical intervention. Symptomatic patients with sliding hiatal hernia present with features of gastroesophageal reflux disease (GERD), which are usually managed with lifestyle modification and proton pump inhibitors. Patients with PEH or mixed hiatal hernias typically present with intermittent dysphagia, substernal discomfort, or abdominal pain, and in rare cases present acutely with gastric volvulus and strangulation. All symptomatic PEH, mixed, and complex hiatal hernias require operative intervention to avoid life-threatening complications. Also see our article “ ”.
Types of hiatal hernias 
Type I: sliding hiatal hernia
- Most common type (95% of cases)
- The GEJ and the gastric cardia slide up into the posterior mediastinum.
- The gastric fundus remains below the diaphragm (hourglass stomach)
Type II: paraesophageal hiatal hernia
- Part of the gastric fundus herniates into the thorax.
- The GEJ remains in its anatomical position below the diaphragm.
Type III: mixed hiatal hernia
Type IV: complex hiatal hernia
- Herniation of any abdominal structure other than the stomach (e.g., spleen, omentum, or colon)
- Rarest type
- Esophageal hiatus
Gastroesophageal junction (GEJ)
- Normally lies at the level of the esophageal hiatus
- Phrenoesophageal ligament (PEL) attaches to the esophagus at the GEJ
Changes in the presence of a hiatal hernia
- Predisposing factors lead to laxity of the esophageal hiatus, e.g.:
- Relative negative intrathoracic pressure and the lax hiatus → herniation of the abdominal contents into the thorax → loss of reflux barrier + compromised fluid emptying of distal esophagus → gastroesophageal reflux disease (GERD) 
- : most sensitive test
Endoscopy: used to diagnose hiatal hernia and evaluate for possible complications (see “Complications” below)
- Z-line: squamocolumnar junction, which represents the transition from the squamous epithelium-lined esophageal mucosa to the columnar epithelium-lined gastric mucosa; corresponds to the GEJ
Other tests that can detect hiatal hernias include 
- Chest x-ray
- CT Thorax: recommended for urgent preoperative evaluation of complicated type II, III, and IV hernias
- Esophageal manometry: helps calculate the size of a sliding hiatal hernia by accurately identifying the level of the diaphragmatic hiatus
- gastroesophageal reflux : not a diagnostic test; useful for determining the extent of
Management of patients with sliding hiatal hernia
- Conservative management
- Surgery: laparoscopic/open fundoplication and hiatoplasty ; 
Management of patients with types II, III, IV hiatal hernias 
Complications of type I
- Arise from long-standing gastroesophageal reflux (see "Complications” in “”)
Complications of type II, III, IV
- (occult/massive) → iron deficiency anemia 
- Gastric volvulus 
- Total gastric obstruction
The complications of types II, III, and IV are often medical emergencies.
We list the most important complications. The selection is not exhaustive.