Voluntary or involuntary forceful expulsion of stomach contents in a retrograde fashion up to and out of the mouth.

Results in forceful expulsion of gastric contents from relaxation of the stomach, esophageal sphincter and pylorus, with the simultaneous contraction of the abdominal musculature, and retroperistalsis of the small intestine.

Occurs independently from nausea but most often are associated.

Retching is the rhythmic spasmodic movement of the diaphragm and abdominal muscles, in the absence of gastric content expulsion.

Associated with neurotransmitters acetylcholine, histamine, serotonin and dopamine.

Commonly associated adverse reaction to medications such as NSAIDs, chemotherapy agents, antidepressants, analgesics, antibiotics, and hormonal therapy.

Commonly associated with bacterial and viral infections.

The brain and GI tract particularly associated with nausea and vomiting.

Nausea is a cerebral sensation, while vomiting is a brain stem response.

The motor control of the gut involved at three levels: the parasympathetic ans sympathetic nervous system, the smooth muscle cells and the enteric brain neurons.

The stomach lining, the chemoreceptor trigger zone in the floor of the fourth ventricle, the vestibular apparatus and the brain cortex all involved with the physiology of nausea.

The final common pathway from the above four areas is the vomiting center, causing the neuromuscular reflex.

All four neurotransmitters are located in the chemoreceptor trigger zone, and the lining of the gastrointestinal tract.

Serotonin is particularly important in the gastrointestinal tract, while acetylcholine and histamine are important in the vestibular apparatus.

Cortex mediated nausea/vomiting not associated with specific neurotransmitters.

Usually preceded by nausea.

Known as emesis.

Retching which is the repetitive contraction of the muscles of the diaphragm and abdominal wall often precedes or accompanies vomiting.

Mediated by efferent stimuli from the vomiting center in the brain and associated with neurotransmitters acetylcholine, histamine, serotonin and dopamine.

Most episodes acute and self-limited.

Causes numerous and varied and include: 1-medications-analgesics, anesthetics, antiasthmatics, anticonvulsants, antidepressants, anti-inflammatory, antimicrobials, antiparkinsonian drugs, cancer chemotherapy agents, cardiovascular drugs, corticosteroids, diabetic drugs, ergot alkaloids, gastrointestinal drugs, hormonal agents, iron replacement drugs, substance abuse agents: 2-infections: 3-gastrointestinal disorders: 4-CNS disorders: 5-Psychologic/Psychiatric disorders: 5-medical diseases-cardiac, genitourinary, endocrine, metabolic, and pregnancy: 6-postoperative: 7-radiation therapy: 8-idiopathic.

Acute onset suggests viral gastroenteritis, pancreatitis, biliary tract disease, or drug reaction.

Insidious onset related to gastroesophageal reflux disease, gastroparesis, metabolic disorders and pregnancy.

Nausea and vomiting may occur with increased intracranial pressure, acute labyrinthitis, Ménèire’s disease and motion sickness.

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