Nature of antireflux barrier formed by Nissen fundoplication surgery

Nissen fundoplication is an effective surgical treatment for the treatment of gastroesophageal reflux disease but the exact mechanism by which it works remains debatable. We determined the effects of Nissen (360° wrap) and Toupet (270° wrap) fundoplication on the esophagogastric junction (EGJ) pressure in response to distension of the stomach in an ex-vivo preparation of the porcine esophagus and stomach. The duodenal opening was sealed, and stomach cannulated for gas insufflation using a barostat device. The effect of gastric distension on the EGJ was measured, before and after fundoplication, using high-resolution esophageal manometry impedance (HRMZ) catheter as well as with the functional luminal imaging probe (FLIP). Prior to fundoplication, insufflation of the stomach resulted in an immediate leakage of gas through the esophageal orifice with minimal gastric distension. Following fundoplication, the stomach distended like a balloon without leakage of air through the esophagus. The HRMZ recordings show an increase in the EGJ pressure with gastric distension that was 2-3 times higher than the increase in gastric pressure. The FLIP detected a graded decrease in the EGJ distensibility with gastric distension following fundoplication. We propose a novel mechanism by which fundoplication builds a mechanical barrier at the EGJ "sphincter like valve" to strengthen the anti-reflux barrier function.