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Gastric Motility Disorders

Gastroparesis

  • Absence of Organic Causes:
    • No stricture, ulcer, tumor, superior mesenteric artery syndrome, or mechanical obstruction
  • Absence of Non-Organic Causes:
    • Functional dyspepsia, rumination syndrome, cyclic vomiting syndrome, or bulimia/anorexia nervosa

Gastric Motility

  • Fasting:
    • Migrating Motor Complex (MMC)
  • Feeding:
    • Accommodation and receptive relaxation
  • Postprandial:
    • Antral mill

Fasting Motility

  • Migrating Motor Complex (MMC):
    • Consists of slow waves and action potentials
  • Phases of MMC (Total 90 minutes):
    • Phase I: Motor quiescence (40 minutes)
    • Phase II: Irregular contractility (40 minutes)
      • Slow waves originate in pacemaker at the greater curvature, mid body
      • Slow waves: 3 cycles/min (stomach); 10 cycles/min in the duodenum, propagating at 5-10 cm/min to the terminal ileum in 1.5 hours
      • Circumferential and antegrade movement
    • Phase III: Organized, strong propulsive contractions (10 minutes)
      • MMCs originating in the stomach are more likely to propagate distally than those originating in the small bowel
      • Phase III contractions help propel air, digestive fluids, debris, and gut flora distally, preventing stasis and bacterial overgrowth
      • Motilin (from M cells in proximal small bowel) is the primary hormone for Phase III of MMC
      • Motilin has 50% sequence homology with Ghrelin
  • Accommodation / Adaptive Relaxation:
    • Involves the fundus via a local reflex arc
    • Remains intact after vagotomy
  • Receptive Relaxation:
    • Involves the body of the stomach
    • Abolished by vagotomy
  • Effect on Emptying:
    • Decreased emptying time for liquids

MCQ: True Statements About Gastric Motility

Question:

Following are true except:

  1. MMC occur during fasting
  2. Receptive relaxation is in fundus
  3. Accommodation is intact after vagotomy
  4. CGRP in vagal efferents are primary mediators of post-op ileus

Answer:

2) Receptive relaxation is in fundus

Explanation:

  • Receptive relaxation occurs in the body of the stomach, not the fundus.
  • MMC (Migrating Motor Complex) indeed occurs during fasting.
  • Accommodation (adaptive relaxation in the fundus) is intact after vagotomy.
  • CGRP (Calcitonin Gene-Related Peptide) is a primary mediator in post-operative ileus through its role in vagal efferents.

Risk Factors for Gastroparesis

  • Gender:
    • More common in females than males (4:1 ratio)
  • Average Age:
    • Typically diagnosed around 34 years
  • Common Causes:
    • Idiopathic (most common)
    • Diabetes (accounts for one-third of cases)
      • Often associated with 10 years of diabetes (DM)
    • Post-viral infection
    • Post-surgical (especially following vagotomy, intentional or inadvertent)
    • Parkinson's disease
    • Scleroderma
    • Pseudo-obstruction

Gastric Emptying Studies

  • Gold Standard:
    • Nuclear medicine solid-phase gastric emptying test
  • Diagnostic Criteria:
    • >50% of a solid meal is retained 2 hours after ingestion
    • >10% of a solid meal is retained after 4 hours
  • Test Meal:
    • Radionuclide eggbeater meal (250 kcal, low fat) is used as the test meal
  • Accuracy:
    • Liquid emptying is considered less accurate than solid-phase tests

Management of Gastroparesis

  1. Correct Underlying Conditions:
    • Hyperglycemia and electrolyte imbalances
    • Start with a liquid diet to ease gastric emptying
  2. Pharmacological Management:
    • Metoclopramide:
      • Only FDA-approved drug for gastroparesis
      • Central action: D2 antagonist (at the CTZ)
      • Peripheral action: 5HT3 antagonist / 5HT4 agonist
    • Erythromycin:
      • Acts as a motilin agonist
      • Targets gastric antrum and proximal duodenum
      • Issues with decreasing effectiveness over time, gut flora alteration, risk of resistance, and potential cardiac arrhythmias
    • Mitemcinal:
      • An erythromycin-derived motilin agonist
      • Improves gastroparesis symptoms but has no significant improvement over placebo
  3. Ghrelin:
    • Ghrelin and motilin are co-produced in the duodenum and proximal jejunum
    • Ghrelin infusions stimulate gastric contractility and emptying
    • Ghrelin has separate receptors from motilin
  4. Botox Injection:
    • Performed endoscopically
    • Prepyloric region (<2 cm from pylorus) targeted, injected circumferentially
    • Repeated at several months intervals
    • Provides relief for an average of three months
    • Females and older patients respond well
  5. Gastric Pacing:
    • Uses high-frequency and low-energy electrical stimulation
    • Improves symptoms in up to 60% of patients

  6. Enterra Device:

    • Consists of two electrical leads
    • Ideal for patients who have not undergone previous gastric surgery
    • Benefits noticed after several months
    • Leads placed along the anterior greater curvature of the stomach, separated by about 1 cm
    • Most distal electrode located about 10 cm proximal to the pylorus

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MCQ 1: Gastroparesis - Correct Statement

Question:

Which of the following is the correct statement regarding gastroparesis?

  1. Male affected more than females
  2. C13 labelled Octonate/spirulina is the gold standard
  3. Erythromycin is FDA approved for gastroparesis
  4. >50% retention of solid food after 2 hours is diagnostic

Answer:

4) >50% retention of solid food after 2 hours is diagnostic

Explanation:

  • Gastroparesis is diagnosed when >50% of a solid meal is retained 2 hours after ingestion.
  • Females are affected more than males, and C13 labelled Octonate/spirulina is not the gold standard (solid-phase gastric emptying study is).
  • Erythromycin is not FDA-approved for gastroparesis but is used off-label.

MCQ 2: MEDTRONIC (ENTERRA) Gastric Electrical Stimulation - False Statement

Question:

Which of the following is a false statement regarding MEDTRONIC (ENTERRA) gastric electrical stimulation for gastroparesis?

a. FDA approved for intractable (drug-refractory) cases

b. 3 cycles per minute (CPM) is used in this device

c. MRI cannot be done after placement of this device

d. Diabetic gastroparesis has better outcomes than idiopathic gastroparesis cases

Answer:

b) 3 cycles per minute (CPM) is used in this device

Explanation:

  • The MEDTRONIC Enterra device operates at 12 cycles per minute (CPM), not 3.
  • It is FDA approved for drug-refractory cases, MRI cannot be performed after placement, and diabetic gastroparesis generally shows better outcomes compared to idiopathic cases.