There are two types of peristaltic contractions: primary and secondary. The primary peristaltic wave helps to move food forward. The secondary peristaltic wave initiates if the primary peristaltic wave does not work, and food is not able to pass. Due to the distention of the esophagus, stretch receptors become stimulated, and the secondary wave clears the bolus.

The stretching of the gut stimulates peristalsis during the development of the food bolus, which activates the ENS, parasympathetic activation, and chemical activation of the gut.

Swallowing partially occurs due to the ENS and has three phases: oral, pharyngeal, and esophageal. During the pharyngeal phase of swallowing, peristalsis first occurs due to the pharynx and then goes to the esophageal phase. Gravity assists with the downward movement of the bolus as well. Gastric peristalsis occurs at the site of the corpus and antrum with peristaltic contractions increasing in the antrum. Intestinal peristalsis occurs in the small and large intestines. In the colon, there is a mass movement, and peristaltic contraction helps to move the chyme. Strong peristalsis is apparent when the stomach and small intestine are empty due to the migrating motor complex (MMC). When there is a lack of MMCs, there can be increased intestinal bacterial growth.[9]

Motility disorders involving peristalsis can be tested by esophageal, antroduodenal, colonic, and anorectal manometry.[12] High-resolution manometry can help clinicians test abnormal and normal peristalsis. A 24 hour pH catheter can also measure acid reflux, which can be due to disorders involving issues with peristalsis.[13] A barium esophagogram is useful for the detection of transit and swallowing.[14]

Disorders involving peristalsis:

Gastroesophageal Reflux Disease (GERD)

GERD occurs when stomach contents travel backward up into the esophagus, which can be due to an impaired lower esophageal sphincter (LES). Normally the LES contracts after the passage of food; however, in GERD, it can remain open, allowing stomach acid to travel in a retrograde fashion. Many factors contribute to GERD, one of which is dysfunctional peristalsis and bolus movement, which is a finding in patients with the condition. Usually, esophageal peristalsis assists in clearing refluxate, but this is not always the case in GERD.[15]

Hirschsprung Disease

In Hirschsprung disease, the ENS is nonfunctional, which can lead to intestinal blockage, among other issues. The ENS controls motility, and a lack of this system, in turn, affects peristalsis where it can no longer function properly, and contents cannot pass. Both the myenteric plexus and submucosal plexus are affected. The risk of Hirschsprung’s disease increases with Down syndrome and normally requires surgery.[16]

Gastroparesis

Gastroparesis occurs when the stomach cannot move its contents forward even without an obstruction. The pathophysiology behind gastroparesis is complex; however, there is a lack of communication between smooth muscle and ICCs, thus affecting peristalsis. Diabetic gastroparesis can also occur. Individuals who have elevated blood glucose levels can have neuronal damage, which affects the myenteric plexus.[17]

Achalasia

Achalasia is a disorder in which the LES does not relax to allow food to travel from the esophagus to the stomach. In both children and adults, achalasia involves dysfunctional peristaltic movement of the esophagus, greater LES pressure, and the inability of the sphincter to relax.[12] A lack of peristalsis is most likely due to the dysfunction of the myenteric plexus in the esophagus. Specifically, there is a problem with inhibitory transmitters preventing peristaltic movement leading to greater excitation, adding to the LES pressure.[18]

Reverse peristalsis (vomiting)

 A factor that leads to the vomiting reflex is reverse peristalsis, and as the name implies, contents are moved backward instead of forward. This action begins in the small intestine and moves towards the stomach.

Abnormal peristalsis can be detected and classified. High-resolution manometry helps to define weak and absent peristalsis. In the recent Chicago classification, weak peristalsis is when there are breaks in 20-mmHg isobaric contours and occurs in greater than twenty percent of swallows. Failed peristalsis is present in greater than thirty percent of swallows.[14]

Peristalsis plays a significant role in multiple common diagnoses that health care professionals see daily. From common disorders including constipation or diarrhea where peristaltic contractions can be decreased or increased to rarer forms of pathologic peristalsis having involvement in Hirschsprung disease, it is an essential aspect of the gastrointestinal system.