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Gastric emptying

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Gastric emptying

Claudia Cheng

updated in August 2006

Introduction

Stomach emptying is a coordinated function by intense peristaltic contractions in the antrum. At the same time, the emptying is opposed by varying degrees of resistance to passage of chyme at the pylorus. Rate depends on pressure generated by antrum against pylorus resistance. Chyme = food in stomach which has been thoroughly mixed with stomach secretions

Factors affecting stomach empyting

  1. Promote

§         Gastric volume

o       Increased food volume in stomach promotes increased emptying

o       Antral distension stimulates vasovagal excitatory reflexes leading to increased antral pump activity

§         Liquid vs solid food

o       Clear fluids are empty rapidly (T1/2 » 30 minutes). Solids stay in stomach longer (T1/2  » 1-2 hours)

o       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

o       Protein empties fastest, followed by carbohydrates. Fats take longest to empty

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

§         Hormonal factors

o       Gastrin has mild to moderate stimulatory effects on motor functions in the body of the stomach. Enhances activity of pyloric pump

o       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

o       Parasympathetic innervation (via vagus) stimulates motility

o       Local myenteric reflex

§         Drugs

o       Prokinetics eg cisapride, erythromycin metoclopramide

  1. Inhibit

§         Duodenal distension

o       Results in inhibitory enterogastic reflexes

o       Slow or even stop stomach emptying if the volume of chyme in the duodenum becomes too much

§         Osmolarity of chyme

o       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

o       Fat and protein breakdown products in the small intestine inhibits gastric emptying

§         Acid

o       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

o       Cold liquid (40C) empty more slowly

§         Hormones

o       Cholecystokinin released from duodenum in response to breakdown products of fat and protein digestion. Blocks the stimulatory effects of gastrin on the antral smooth muscle

o       Secretin released from the duodenum in response to acid, has a direct inhibitory effect on the gastric smooth muscles

o       Others eg somatostatin, vasoactive intestinal peptide (VIP), gastic inhibitory peptide (GIP)

§         Neural

o       Sympathetic nerves (via the celiac plexus) inhibits motility

§         Patient factors

o       Pregnancy delays gastric emptying (progesterone)

o       Anxiety delays gastric emptying

o       Pain

o       Elderly

o       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

 Ó Claudia Cheng August 2006


©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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