ABSTRACT
Vomiting is the forcible expulsion of gastric contents from the mouth. It is often preceded by the unpleasant sensation of nausea. Vomiting is mediated by the emetic centre in the medulla, which receives afferent neurons from the gastrointestinal tract, the chemoreceptor trigger zone in the medulla, the vestibular apparatus and the cerebral cortex. There are six main stimuli that cause nausea or vomiting: distension or obstruction of a hollow organ; exposure of the gastrointestinal mucosa to an irritant or toxic substance; stimulation of the chemoreceptor trigger zone; abnormal stimuli arising from the vestibular system; raised intracranial pressure; and cerebral factors. Abdominal USS or computed tomography (CT) scan may reveal gallstones, renal calculi, gastrointestinal tumours or other intra-abdominal pathology. CT of the brain may visualise a thromboembolic stroke, intracranial haemorrhage, tumour or other space-occupying lesion. Staining for acid-fast bacilli and CSF mycobacterial culture should be performed if tuberculous meningitis is a possibility.
