Posterior vagal trunk

Posterior vagal trunk refers to the continuation of right vagus nerve as it follows the esophagus through the esophageal hiatus of the diaphragm to enter into the abdominal cavity. Similarly, the anterior vagal trunk is a continuation of the left vagus nerve. The relocation of the right and left vagi onto the posterior (dorsal) and anterior (ventral) surfaces of esophagus is due to the rotation of the gut inside abdominal cavity.

The two vagal trunks communicate with each other via posterior and anterior communicating branches, forming peri-esophageal plexus superior to the esophageal hiatus.

Both vagal trunks–posterior and anterior–contain parasympathetic motor and visceral afferent neurons:

• The parasympathetic fibers are preganglionic neurons which arise from the dorsal motor nucleus of vagus inside medulla oblongata in the brainstem. They join the prevertebral plexus around the aorta and its branches, however, do not synapse over here. Thereupon, preganglionic parasympathetic neurons of the posterior vagal trunk get distributed to various parts of foregut, midgut, associated viscera and celiac plexus. Here, they synapse with post-ganglionic neurons of the local enteric nervous system within the gut wall. Even though the enteric nervous system can regulate and coordinate gastrointestinal secretion and peristalsis independently, the parasympathetic neuronal input from the vagal trunks can hugely modulate its working to cause increased peristalsis and secretions.

• The visceral afferent fibers bring in sensory information from the foregut and the midgut, including sensations of gut fullness, nausea and probably pain. They also traverse through prevertebral plexus, en-route to the central nervous system.

Injuries to posterior and anterior vagal trunks during procedures, such as myotomy and gastric fundoplication could result in delayed gastric emptying and sometimes post-vagotomy diarrhea.