José (Pepe) Boix-Ochoa - Dr., Professor, Secretary General / Treasurer World Federation of Associations of Pediatric Surgeons (WOFAPS), Barcelona, Spain.
Founding Member of the European Union of University Surgical Professors.
Honorary Professor and Visiting Professor in 39 Universities (outside Spain).
Honorary Member and Honorary Fellowship in 49 National and International Societies of Surgery and Paediatric Surgery.
Member of 14 Editorial Boards of Pediatrics, General Surgery, Pediatric Gastroenterology and Pediatric Surgery.
Honorary Member and Guest-Speaker of the American Pediatric Surgical Association (APSA), American Academy of Pediatrics (AAP) and American Academy of Pediatric Gastroenterology (AAPG).
Boix-Ochoa has identified 6 factors which comprise the antireflux barrier. All of these operate over an area from 3 to 7 cm and represent what is generally referred to as the Lower Esophageal Sphincter (LES):
1. Pinch-Cock Action – The right crus of the diaphragm forms a sling-shaped orifice around the esophagus. During deep inspiration, this pulls the esophagus to the right and downward with deep inspiration, thus narrowing the esophageal lumen. This is affected by paralysis of the diaphragm.
2. Intraabdominal Esophagus – Felt by Boix-Ochoa to be the key to the LES, and to successful fundoplication. It determines the length of esophagus exposed to intraabdominal pressure and, therefore, the length of “esophageal valve” holding back potential refluxate. A sufficient segment of abdominal esophagus is considered >2 cm; a mechanically incompetent LES has an abdominal length <1 cm, or an overall sphincter length <2 cm. At birth, the total length of the LES ranges from 0.5-1cm and increases to 2.5-3 cm by 3 months of age. This will be shortened in hiatal hernia, short esophagus, gastrostomy, and esophageal atresia.
3. Angle of His – at the junction of the esophagus and the stomach. In a child with a normal-sized intraabdominal esophagus, this angle is acute. With an acute angle, when a child vomits, more contents strike the fundus than escape via the esophagus. The resulting pressure in the fundus further increases the acuity of the angle, shutting off the esophagus. In conditions such as short esophagus, hiatal hernia, and esophageal atresia the angle is obtuse, and the fundus actually acts as a funnel into the esophagus, allowing reflux at much lower intragastric pressures.
4. Mucosal Rosette – signifies redundant folds of mucosa at the gastroesophageal junction, present only when a normal angle of His is present. With increased intragastric pressure or negative intrathoracic pressure, these folds squeeze together to form a weak antireflux valve.
5. High Pressure Zone – an area of increased muscular thickness near the gastroesophageal junction, it is described as a manometric sphincter. The basal tone of the HPZ increases until 45 days of age, at which time maturation is complete. Of note, this tone reaches maturity at the same time regardless of gestational age; thus, an immature HPZ CANNOT explain the increased incidence of GER in preemies.
6. Abdominal Pressure – Intraabdominal pressure between 6-8 cm H2O is necessary to maintain a competent LES by collapsing the intraabdominal segment. Conditions where intraabdominal pressure is lacking (e.g., omphalocele, gastroschisis, muscular weakness) will result in GER. Under normal circumstances, elevated intraabdominal pressure will NOT cause reflux (not to be confused with intragastric pressure, which will cause reflux when elevated).
Maturation of the LES and gastroesophageal competence are achieved between 5-7 weeks of life, regardless of gestational age or birthweight. Thus, reflux is physiologic in infants less than 6 weeks old, and fundoplication is contraindicated prior to age 6 weeks.
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