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 (5-HT3 and Ach Mediated – Treatment: Promotilants, 5-HT3 Antagonists)
- Ingestion of irritants:
bacteria, e.g. salmonella (gastroenteritis)
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