Vomiting

Involuntary forcible expulsion of stomach contents through the mouth. Vomiting may be preceded by nausea, pallor, sweating, excessive salivation, and slowed heart-rate. It occurs when the vomiting centre in the brainstem is activated by signals from 1 of 3 places in the body: the digestive tract; the balancing mechanism of the inner ear; or the brain, either due to thoughts and emotions or via the part of the brain that responds to poisons in the body. The vomiting centre sends messages to both the diaphragm, which presses down on the stomach, and the abdominal wall, which presses inwards, thereby expelling the stomach contents upwards through the oesophagus. Vomiting may be due to overindulgence in food or alcohol, is a common side effect of many drugs, and may follow general anaesthesia. Vomiting is also common in gastrointestinal disorders such as peptic ulcer, acute appendicitis, gastroenteritis, and food poisoning. Less commonly, it is due to obstruction (see pyloric stenosis; intussusception) or a tumour of the digestive tract. It may also be due to inflammation (see hepatitis; pancreatitis; cholecystitis). Other possible causes are pressure on the skull (see encephalitis; hydrocephalus; brain tumour; head injury; migraine), conditions affecting the ear’s balancing mechanism (see Ménière’s disease; labyrinthitis; motion sickness), and hormonal disorders (see Addison’s disease). Vomiting may be a symptom of ketoacidosis in poorly controlled diabetes mellitus. It may also be a symptom of an emotional problem or be part of the disorders anorexia nervosa or bulimia. Persistent vomiting requires medical investigation. Treatment depends on the cause. Antiemetics may be given. (See also vomiting blood; vomiting in pregnancy.)