9 Vomiting

Definitions
Vomiting is defined as the involuntary return to, and forceful expulsion from, the mouth of all or part of the contents of the stomach. Waterbrash is the sudden secretion and accumulation of saliva in the mouth as a reflex associated with dyspepsia. Retching is the process whereby forceful contractions of the diaphragm and abdominal muscles occur without evacuation of the stomach contents.
KEY POINTS
• Vomiting is initiated when the vomiting centre in the medulla oblongata is stimulated, either directly (central vomiting) or via various afferent fibres (reflex vomiting).
• Vomiting of different origins is mediated by different pathways and transmitters. Therapy is best directed according to cause.
• Consider mechanical causes (e.g. gastric outflow or intestinal obstruction) before starting therapy.
Important diagnostic features
Central vomiting
• Drugs, e.g. morphine sulphate, chemotherapeutic agents.
• Uraemia.
• Viral hepatitis.
• Hypercalcaemia of any cause.
• Acute infections, especially in children.
• Pregnancy.
Reflex vomiting
Gastrointestinal causes (5HT3 and Ach mediated— treatment: promotilants, SHT3 antagonists)
• Ingestion of irritants.
Bacteria, e.g. salmonella (gastroenteritis).
Emetics, e.g. zinc sulphate, ipecacuanha.
Drugs, e.g. alcohol, salicylates (gastritis).
Poisons, e.g. salt, arsenic, phosphorus.

• PUD: especially gastric ulcer; vomiting relieves the pain.
• Intestinal obstruction.
Hour-glass stomach (carcinoma of the stomach). Pyloric stenosis—infant: hypertrophic pyloric stenosis, projectile vomiting; adult: pyloric outlet obstruction secondary to PUD or malignant disease.
Small bowel obstruction: adhesions, hernia, neoplasm, Crohn’s disease.
Large bowel obstruction: malignancy, volvulus, diverticular disease.
• Inflammation: appendicitis, peritonitis, pancreatitis, cholecystitis, biliary colic.
General causes (ACh and D2 mediated—treatment:
anticholinergics, antidopaminergics)
• Myocardial infarction.
• Ovarian disease, ectopic pregnancy.
• Severe pain (e.g. kick to the testis, gonadal torsion, blow to the
epigastrium).
• Severe coughing (e.g. pulmonary TB, pertussis).
CA’S causes UVAdr andACh mediated—treatment:
anticholinergics, sedatives)
• Raised intracranial pressure.
Head injury.
Cerebral tumour or abscess.
Hydrocephalus.
Meningitis.
Cerebral haemorrhage.
• Migraine.
• Epilepsy.
• Offensive sights, tastes and smells.
• Hysteria.
• Middle ear disorders (H2 mediated—treatment: antihistamines). Menière’s disease.
Travel/motion sickness.