Which of the following is true about gastric emptying?

Which of the following is true about gastric emptying?

A. Decreased by cholecystokinin
B. Decreased by gastrin
C. Increased by secretin
D. Increased by GIP


Answer is A. Decreased by cholecystokinin

Factors affecting stomach empyting include those which promote and those which inhibit it.


Factors that promote gastric emptying are:

• Gastric volume
• Increased food volume in stomach promotes increased emptying
• Antral distension stimulates vasovagal excitatory reflexes leading to increased antral pump activity
• Liquid vs solid food: Clear fluids empty rapidly (T1/2 » 30 minutes). Solids stay in stomach longer (T1/2 » 1-2 hours)
• Pylorus is open enough for H2O/fluids to empty with ease. Constriction of the pyloric sphincter to solids until chyme is broken down into small particles and mixed to almost fluid consistency
• Types of food
• Protein empties fastest, followed by carbohydrates. Fats take longest to empty

          Note: high protein food especially meat stimulate release of gastrin from antral mucosa

• Hormonal factors
• Gastrin has mild to moderate stimulatory effects on motor functions in the body of the stomach. Enhances activity of pyloric pump
• Motilin released by epithelium of the small intestine enhances the strength of the migrating motor complex which is a peristaltic wave that begins within the oesophagus and travels thru the whole GIT every 60-90 min during the interdigestive period. Help empty remaining food in stomach
• Neural
• Parasympathetic innervation (via vagus) stimulates motility
• Local myenteric reflex
• Drugs - Prokinetics eg cisapride, erythromycin, metoclopramide

Factors that inhibits gastric emptying are:

• Duodenal distension results in inhibitory enterogastic reflexes. It can slow or even stop stomach emptying if the volume of chyme in the duodenum becomes too much.
• Osmolarity of chyme - Iso-osmotic gastric contents empty faster than hyper or hypo-osmotic contents due to feedback inhibition produced by duodenal chemoreceptors (hyper more inhibitory than hypo)
• Types of food - Fat and protein breakdown products in the small intestine inhibits gastric emptying
• Acid - pH of chyme in the small intestine of < 3.5-4 will activate reflexes to inhibit stomach emptying until duodenal chyme can be neutralized by pancreatic and other secretions
• Temperature - Cold liquids (40 degreee C) empty slowly as compared to warmer liquids
• Hormones 
• Cholecystokinin is released from duodenum in response to breakdown products of fat and protein digestion. It blocks the stimulatory effects of gastrin on the antral smooth muscle and hence decreases gastric emptying.
• Secretin released from the duodenum in response to acid, has a direct inhibitory effect on the gastric smooth muscles
• Others eg somatostatin, vasoactive intestinal peptide (VIP), gastic inhibitory peptide (GIP)
• Neural
• Sympathetic nerves (via the celiac plexus) inhibits motility
• Patient factors
• Pregnancy delays gastric emptying (progesterone)
• Anxiety delays gastric emptying
• Pain
• Elderly
• Disease states eg diabetes mellitus (autonomic neuropathy), post-operative bowel surgery with resultant ileus, high intra-abdominal pressure
• Drugs eg. opioids
• Mechanical eg pyloric stenosis