Parahiatal Hernia

Excerpt

Parahiatal hernia (PHH) is a rare diaphragmatic hernia, an abnormal protrusion of the viscera through an abnormal diaphragmatic defect between the left part of the right and left crura. The diaphragm is a vital muscle for breathing, derived from the septum transversum (anterior portion), pleuroperitoneal folds (posterolateral part), and dorsal mesentery (posteromedial part). This anatomical barrier between the thoracic and abdominal cavities has regular openings for various structures. The hiatal opening at the 10th thoracic vertebral level allows the esophagus to pass through its right crus to form the gastroesophageal junction (GEJ). A PHH typically occurs on the left side of the GEJ. Due to its proximity, PHH always gets confused with a hiatus hernia (see Image. Endoscopic View of a Parahiatal Hernia).

Hiatus Hernia

Most diaphragmatic hernias are hiatal defects. The most prevalent type is the sliding type, characterized by the cephalad migration of the GEJ (Type I). A less frequent variant is the paraesophageal type, with the stomach rolling without (Type II) or with GEJ migration (Type III). In the worst case, diaphragmatic hernia is associated with herniation of other abdominal viscera and the stomach (Type IV). A hiatal hernia's distinctive feature is an abnormal viscera protrusion through a normal opening (esophageal hiatus) in contrast to PHH. The stomach is generally the only herniated content in a hiatal hernia, with other viscera, including the transverse colon, omentum, small bowel, and spleen, rarely found.