Motility Disorders Flashcards
How do you assess esophageal motility?
- Esophageal manometry
- Currently termed high-resolution esophageal manometry
- This test is performed using a transnasal, intraluminal manometry catheter containing pressure sensors spaced closely together
- Once positioned from the nares into the stomach, assessment of esophageal motility is made as patient swallows repeated small boluses of water
- This eval assesses the esophageal body peristalsis and upper and lower esophageal sphincter function
What is achalasia?
- Prototypcial esophageal motility disorder
- Results from inflammatory destruction of neurons in the myenteric plexuses of the esophagus
- Destruction predominantly involves the nitric oxide-producing, inhibitory neurons that affect the relaxation of esophageal smooth muscle and spare the cholinergic neurons that contribute to the lower esophageal sphincter tone
- Loss of inhibition at the LES leads to the cardinal defect = failure of appropriate LES relaxation after swallowing
- In the esophageal body, this results in aperistalsis
- Symptoms result from impairment of LES relaxation and resultant esophagogastric function outflow obstruction
What is the upper esophageal sphincter?
• (UES) The major elements of the analysis of upper esophageal sphincter are:
○ Degree of UES relaxation
§ Measured by the nadir UES pressure
○ Magnitude of the intrabolus pressure
§ As a measure of the resistance to flow across the UES
○ Presence or absence of pharyngeal peristalsis
How do you assess the function of the lower esophageal sphincter?
• Analysis of LES function involves determination of its location, basal pressure and degree of relaxation
How do you assess esophageal body motor function?
- Esophageal motor function is assessed by the amplitude and propagation of the pressure waves
- These two parameters can be used to determine the presence and success rate of peristalsis
What are the esophageal manometry findings that establish the dx of achalasia?
• Incomplete relaxation of the LES aperistalsis in the smooth muscle esophagus
Why does scleroderma mess up GI motility?
• Multi-system disorder predominantly associated with skin and GI tract involvement
• Associated with alterations of the microvasculature, the autonomic nervous system and the immune system with a downstream consequence of fibrosis
• Initially small vessel vasculitis that leads to vascular derangement and resultant smooth muscle atrophy and finally fibrosis
• Enventually the entire smooth muscle section of GI tract is susceptible and 90% of patients with scleroderma have GI tract involvement
• In the esphagus - atrophy of the lower 2/3 of esophagus
• Also atrophy and hypotension of the LES
○ GERD and troubles swallowing
○ Eventually GERD creates strictures and makes swallowing even worse
How does esophageal manometry distinguish scleroderma from achalasia?
• Weakened LES in scleroderma vs. a hypertensive LES in achalasia
What is meant by spastic disorders of the esophagus?
- Uncoordinated peristalsis for some reason
- Manometry shows inappropriate pressures for too long or too early
- Patients report difficulty swallowing because the peristalsis isn’t pushing the bolus down properly
What nervous system structures need to be coordinated to create proper gastric motility?
- Parasympathetic
- Sympathetic
- Enteric
What happens in the proximal stomach when food first enters?
- Proximal stomach = cardia, fundus, body
* Receptive relaxation - very little intragastric pressure increase when food first hits the fundus
What’s the major function of the distal stomach?
- Distal - gastric and antrum
- Controls mechanical and some limited enzymatic digestion
- Contraction in distal stomach also regulates gastric emptying into duodenum
- Remember that delivery of chyme to duodenum is not to exceed the rate of small intestine digestion
What mediates receptive relaxation in the proximal stomach?
- This facilitates the food storage role of the stomach
- Occurs when a peristaltic wave reaches the lower esophageal sphincter and is largely mediated by vagal nerve fibers via stimulation of mechanoreceptors
- Mechanoreceptors initiate a vaso-vagal reflex with is the basis for the decrease in gastric accommodation post-vagotomy
Describe the peristaltic movements of the stomach
• Interstitial cells of Cajal are peristalsis pacemaker cells
○ Reside in the midportion of the gastric body and travel distally towards the pylorus at a frequency of about 3/min
• Contractions at proximal stomach are weak - mixing contents and secretions
• Waves are stronger in antrum where grinding occurs
• Early stages of antral contraction pylorus is open allowing a little chyme to leak out
• Followed by pyloric closure forcing intragastric contents back into antrum
○ Goal is 1-2mm size of globules
What do the interstitial cells of Cajal do to the stomach?
- Gastric peristalsis originates in the pacemaker cells
- Interstitial cells of Cajal are peristalsis pacemaker cells
- Reside in the midportion of the gastric body and travel distally towards the pylorus at a frequency of about 3/min
Can scleroderma affect the stomach too and not just the esophagus?
• Yes, there can be stomach-specific fibrosis of smooth muscle