Vomiting (aka emesis) is the involuntary, forceful expulsion of stomach's contents, through the mouth, and sometimes the nose. Nausea is the feeling one is about to vomit, but doesn't necessarily result in vomiting. Regurgitation (aka posseting) is return of undigested food back up to the mouth, without the force/displeasure of vomiting. D&V is shorthand for diarrhea and vomiting.

• Vomitus includes:
  • Gastric secretions, which are highly acidic
  • Recent food intake
  • Malodorous

• Vomiting is caused by stimulation of receptors in the chemoreceptor trigger zone, on the floor of the 4th ventricle of the brain, known as the area postrema
• The area postrema is a circumventricular organ (i.e. structures in the brain charcterized by their extensive vasculature, and lack of normal BBB, allowing for linkage between the CNS and the peripheries), and thus can be stimulated by blood-borne drugs, that can stimulate or inhibit vomiting
• There are various inputs to the vomiting center, including:
  • Stimulation of different receptors in the chemoreceptor trigger zone (e.g. dopamine D2 receptors, serotonin 5-HT3 receptors, opioid receptors, acetylcholine receptors, substance P), in different pathways, in which the final common pathway involves substance P
  • Vestibular system, sends information to the brain via CN8 (vestibulocochlear), which plays a major role in motion sickness, and is rich in muscarinic and histamine H1 receptors
  • CN10 (vagus) is activated when the pharynx is irritated, causing a gag reflex
  • Vagal and enteric nervous system inputs information regarding the state of the GI system. Irritation of the GI mucosa by chemotherapy, radiation, distension, or acute infectious gastroenteritis activates 5-HT3 receptors of these inputs
  • CNS mediates vomiting that arises from psychiatric disorders and stress from higher brain centers

• Digestive, including:
  • Gastritis
  • Gastroenteritis
  • GERD (gastroesophageal reflux disease)
  • Bowel obstruction
  • Overeating
  • Food allergies (often also causing hives/swelling), including allergic reaction to cow's imlk protein (milk allergy, lactose intolerance)
  • Cholecystitis, pancreatitis, appendicitis, hepatitis
  • Food poisoning
• Systemic, as in:
  • Brain tumor
  • Elevated ICP (intracranial pressure)
  • Overexposure to ionizing radiation

• Contents:
  • Fresh blood, called hematemesis, is vomit that is bright red, and suggests bleeding from the esophagus
  • Dark red vomit with liver-like clots, suggests profuse bleeding in the stomach, e.g. from a perforated ulcer
  • Coffee ground vomiting, where there is altered blood resembling coffee grounds, as the iron in the blood is oxidized. This suggests bleeding in the stomach, because the gastric acid has had time to change the composition of the blood
  • Bile, is vomit that is green or yellow, which can enter vomit during subsequent heaves due to duodenal contraction if the vomiting is severe. It indicates the pyloric valve is open, and bile is flowing into the stomach from the duodenum. Sometimes, gastric contents can have a yellow tinge, which is not bile. It can indicate:
    • Mechanical bowel obstruction
    • Volvulus
    • Bowel ischemia
  • Fecal vomiting (aka stercoraceous vomiting, copremesis) is vomiting, in which partially or fully digested matter is expelled from the intestines, into the stomach. It is often a consequence of intestinal obstruction or a gastrocolic fistula. Though it is not usually fecal matter that is expelled, it smells noxious
  • Dry heaves (non-productive emesis) is where the vomiting reflex continues for an extended period with NO appreciable vomitus. It can be painful and debilitating
• Projectile vomiting is vomiting that ejects the gastric contents w/ great force. It is a classic Sx of infantile hypertrophic pyloric stenosis, in which it typically follows feeding and can be so forceful that some materials exits through the nose

• Antiemetics to suppress nausea/vomiting
• Where dehydration results, rehydration/IV fluids

• Aspiration of vomit
• Dehydration and electrolyte imbalance, as prolonged and excessive vomiting depletes the body of water, and alters electrolyte status
  • Gastric vomiting directly causes loss of acid (H+) and chloride (Cl-) directly. Alkaline tide is where normally after eating a meal, the stomach's parietal cells will produce bicarbonate ions (alongside HCl), which is basic, thereby increasing blood pH. This causes hypocholeremic metabolic alkalosis (i.e. low Cl, basic pH, high bicarbonate). This causes the kidney to try compensate for alkalosis (too much +) by excreting more potassium, causing hypokalemia
  • If vomiting of intestinal contents occurs, which is less frequent, this will include bile acids and bicarbonate, and can cause metabolic ACIDOSIS
• Cachexia, if the Pt loses intake of food
• Mallory-Weiss tear
• Dentistry

• Valvular regurgitation
• Diarrhea
• Nausea