Nausea and vomiting
Nausea is the sensation of impending vomiting, whilst retching is the involuntary muscle contractions associated with vomiting, without the expulsion of gastric contents. Vomiting may occur with or without nausea. The causes of nausea and vomiting are diverse, for example alcohol and drugs, motion sickness, pregnancy, many gastrointestinal causes, neurological disorders and myocardial infarction.
Nausea and vomiting can be due to stimulation of the chemoreceptor trigger zones, located in the floor of the fourth ventricle, or by vagal afferents from the gut. These signals stimulate vomiting centres in the medulla.
A history should elucidate the timing, precipitating and relieving factors of the nausea or vomiting and associated symptoms such as abdominal pain. Early morning vomiting is characteristic of pregnancy, but also raised intracranial pressure. Gastrointestinal obstruction may cause vomiting early or late in the condition depending on the site of obstruction. Higher levels of obstruction tend to cause vomiting of less digested food, which occurs more rapidly after eating. Haematemesis is the vomiting of blood, which may appear fresh or partially digested (coffee ground appearance).
A drug history is important as many drugs can precipitate nausea, especially drugs used in chemotherapy. Peptic ulcer disease caused by nonsteroidal antiinflammatory drugs (NSAIDs) may manifest as nausea and vomiting or even haematemesis, and a typical history of epigastric pain may be elicited.