Motility and the Esophagus Flashcards
The GI tract as “Barett’s machine”
Alimentary tract
A muscular tube that extends from the mouth to the anus. The musculature is striated/skeletal muscle in the mouth, pharynx, upper esophagus and pelvic floor and visceral type smooth muscle elsewhere.
Basic structure of the GI tract (in axial cross-section)
Muscularis externa
Outer muscular wrapping of the gut. Consists of an internal circular section and an external longitudinal section. Inbetween these two layers lies the myenteric plexus, aka Auerbach’s plexus.
The submucosal plexus
aka Meissner’s plexus
Located within the submucosa, the layer in between the mucosa and the circular muscle.
Two main types of neuron within the myenteric plexus
Excitator and inhibitory.
Inhibitory innervation involves neurotransmitters such as nitric oxide (NO) and vasoactive intestinal peptide (VIP). These control muscle relaxation.
Excitatory innervation involves mainly acetylcholine. This controls muscle contraction via muscarinic receptor acitvation.
Forces in peristalsis
Requires contraction above the food bolus and relaxation below the food bolus.
Sphincter of Oddi
Connects the biliary tree to the small intestine and releases bile and pancreatic juices when it relaxes.
Ileo-cecal valve
The valve in between the last part of the small intestine the ileum and the large intestine. It opens to allow digested food to past through the intestine and into the colon to create feces
Sphincters and valves of the GI tract
Three functional regions of the esophagus
- Upper esophageal sphincter
- Esophageal body
- Lower esophageal sphincter
The esophageal body is composed of . . .
. . . a mixture of striated and smooth muscle.
The dominant form transitions from striated to smooth as you move down the esophagus.
Phases of swallowing
- Oral preparatory phase
- Oral phase
- Pharyngeal phase
- Esophageal phase
- Lower esophageal sphincter relaxation
Oral preparatory phase of swallowing
Food enters the mouth, mixes with saliva and is formed into a bolus.
While the food is in the oral cavity, the soft palate and base of the tongue are in contact to prevent the bolus from entering the pharynx
This phase is entirely under voluntary neural control
Oral phase of swallowing
Begins with bolus being propelled posteriorly. The tongue tip rises to the hard palate, while the back sinks down posteriorly. This pushes the bolus posteriorly into the pharynx.
The bolus entering the pharynx, along with the extra contact between the tongue and palate, triggers the swallow reflex.
Up to the beginning of the swallow reflex, this is entirely under voluntary control.
Pharyngeal phase of swallowing
Begins as the swallow reflex is triggered. This is a rapid reflex (>1 second) that progresses as follows:
The soft palate elevates and retracts, closing the nasopharynx off. The hyoid bone elevates the larynx which also helps open the UES, while the epiglottis folds down over the laryngeal vestibule. The circopharyngeal muscle relaxes, opening the way to the UES.
Longitudinal contraction of the pharynx brings the UES closer to the base of the tongue. The pharyngeal muscles force the bolus through the UES. Finally, the posterior wall of the pharynx begins a contraction that serves two purposes: 1st, it forces any remaining food through the UES. 2nd, it begins a peristaltic wave that carries through the esophagus.
Once the food has passed the upper esophageal sphincter it immediately closes.
Esophageal phase of swallowing
The peristalsis wave initiated in the pharyngeal phase continues down the esophagus. Upper third of esophagus contracts 1-2 seconds post-swallow, while the lower two-thirds contract 5-8 seconds post-swallow. Peristalsis is triggered by the distension of the esophageal lumen.
Lower-esophageal sphincter relaxation phase
Once the bolus has made its way down the esophagus, the final step is for the lower sphicter to relax. This is induced by vagally mediated inhibition involving nitric oxide as a neurotransmitter. Innervation is by the enteric nervous system (myenteric plexus), Vagus (mediates inhibition and hence relaxation of LES), and the sympathetic nervous system.
Antireflux mechanisms are also operational during this phase.
Antireflux mechanisms of the lower esophageal sphincter
The antireflux barriers include two sphincters within the lower esophageal sphincter or LES, namely, the internal esophageal sphincter and the diaphragmatic sphincter (also called the external esophageal sphincter), and the unique anatomic configuration at the gastroesophageal junction.
Both relax during a swallow, however they can also relax during a reflex called a transient LES relaxation.
Videofluoroscopic Swallow Study
Completed by a speech-language pathologist and radiologist.
The patient eats or drinks various consistencies mixed with barium that provides a real-time view of the swallow. The purpose of this test is to assess the safety and efficiency of the swallow.
The following observations can be made: aspiration (food entering the airway below the vocal folds), penetration (food entering the larynx but not below the vocal folds), and residue (food that remains in the oral cavity or pharynx after the swallow).
Flexible Endoscopic Evaluation of Swallowing
Passing an endoscope transnasally and may be used for diagnostic therapy or to monitor therapy progress. The oral and esophageal phase of the swallow cannot be visualized with FEES. Also, the bolus cannot be visualized during the swallow because of the tissues of the pharynx contact each other during the swallow obscuring the view
Esophagram
X-ray images obtained while a patient swallows barium- may also be called upper GI fluoroscopy.
Serves to identify anatomical problems with the esophagus– any high-grade obstructive lesion, strictures, diverticuli, hiatal hernia, or foreign body lodged in esophagus. Certain esophageal motility disorders may also demonstrate characteristic appearances on esophagram
Upper Endoscopy
Consists of looking directly into the esophagus with a flexible videoscope. It helps identify causes of mechanical obstruction such as malignancy, non-radio opaque foreign bodies, or strictures. It also allows for assessment of mucosal inflammatory changes that may contribute to symptoms, such as infectious, peptic (acid-related), or allergic esophagitis.
Mucosal biopsies may be obtained during endoscopy for histologic evaluation.
Esophageal manometry
During the test, patients take 10 liquid swallows, while the muscular pressure generated by contractions of the esophagus are recorded.
Indications for performing an esophageal manometry include: (1) assessment of esophageal dysmotility and anatomical landmarks, (2) assistance in proper placement of pH monitoring probe for quantifying acid reflux, (3) evaluate for contraindications to anti-reflux or other esophageal surgeries, and (4) prognosticate outcomes of anti-reflux or other esophageal surgeries.
Two main components make up the data collected from an esophageal manometry: (1) the esophageal body and (2) the esophageal sphincters (LES, UES).
High-resolution esophageal manometry
Same idea as normal esophageal manometry, but with more sensors. The advantage is that you get to generate pressure heat maps of the esophagus.
pH probing
A pH catheter can be used to quantify and characterize GER. It is usually reserved for patients who remain symptomatic despite maximal anti-reflux medications and/or for patients with atypical GER symptoms such as hoarseness, chronic cough.
Multiple coordinated measurements are made and are categorized into acid (pH<4) or non-acid (pH>4)
Dysphagia
Swallowing disorder. May lead to complications such as dehydration, malnutrition, airway obstruction, or pneumonia. It is important to characterize dysphagia as solid dysphagia, liquid dysphagia or both.
Solid food dysphagia is usually related to an anatomical abnormality in the esophagus.
Liquid dysphagia usually means there is an anatomical or functional problem with structures relevant to the oral and pharyngeal phases of swallowing.
Dysphagia to both solids and liquids from the onset is likely related to an esophageal motility disorder or a problem with the chewing and swallowing muscles
Algorithm for esophageal motility disorders
GERD due to hiatus hernia
Layers of different organs that make up the GI tract
What is shown at 11’ o clock in this esophageal endoscopy?
An inlet patch - a small patch of gastric mucosa exteding out of the stomach proximal to the upper esophageal sphincter.
This is a normal anatomical variant and is not associated with any pathology.
Laryngeal cleft
Congenital connection between the larynx and esophagus that results in the larynx being ‘stuck’ open a crack. Requires surgery in order to diagnose.
This causes aspiration of thin fluids, but sticking to food and thicker fluids can help avoid aspiration. Slowing the rate of fluid consumption also helps to avoid (for infants this means using a special sippy cup lid).
Patients presents with fever and odynophagia with severe throat pain at rest. Esophageal ulcers are revealed on upper endoscopy and biopsied. Below is the specimen. What is the likely diagnosis?
Herpetic esophagitis
Note that HSV-1 is usually the causative agent, and that the appearance on biopsy is large, polyploid epithelial cells with lobular, ground-glass, pink-purple nuclei showing viral inclusion bodies. Often accompanied by local neutrophilic inflammation and systemic lymphocytosis.
Note that with HSV, this could be a primary infection or a reactivation.
Patient presents with 3 months of daily heartburn refractory to H2 blockers. They are referred for endoscopy where they have apparent LES-proximal acid burn. The biopsy below is obtained. What is the likely diagnosis?
Reflux esophagitis
Note the features of the pathology: Acanthosis and basal cell hyperplasia, with much larger and more euchromatic nuclei all the way up the epithelium. There is also local eosinophilia and lymphocytic inflammation, likely Th2.
Eosinophilia restricted to the lower esophagus proximal to the EGJ is highly specific for reflux esophagitis.
The following image is observed on video fluoroscopic swallow study. What is the interpretation?
Penetration of fluid into the larynx.
Likely causative of a liquid-only dysphagia.
What pathology is indicated by this esophageal manometry?
Achalasia
What pathology is indicated by this esophageal manometry?
ALS or other neuropathic condition affecting somatic muscle
Early ALS often presents as dysphagia due to inability to open the UES. May also present as speech pathology.
The following is seen in upper GI fluoroscopy. What is the likely diagnosis?
Achalasia
This is referred to as the “bird’s beak” sign
Nissen Fundoplication
May be done if LES is too consistently relaxing in order to increase the LES pressure and make reflux less frequent.
Note that 11% of procedures result in iatrogenic dysphagia, and may result in difficulty clearing gastric gas, which may be very uncomfortable.
What pathology is indicated by this esophageal manometry?
Scleroderma
Scleroderma dysphagia presents this way due to interference with nerve conduction due to fibrosis around the myenteric plexus.
What pathology is indicated by this esophageal manometry?
High-pressure peristalsis and difficulty opening the LES. This will likely result in substantial dysphagia.
This is sometimes an iatrogenic effect of the fundoplication procedure or similar procedures used to treat excessive LES relaxation.
