Nausea and Vomiting

Nausea and vomiting are symptoms rather than diseases. They can result from many different conditions, such as infection, food poisoning, motion sickness, overeating, intestinal obstruction, brain injuries, appendicitis, and migraine headaches. They can also be symptoms associated with more serious medical conditions such as heart attacks, central nervous system disorders, kidney and liver diseases, and cancer. Nausea is the subjective feeling of the need to vomit; however, it does not always lead to vomiting. Vomiting, or emesis, is the forcible voluntary or involuntary [Page 1211]oral expulsion of upper gastrointestinal contents due to contraction of the gut and thoracoabdominal wall musculature.

There are many activators of emesis and these stimuli can act at several anatomic sites. Emesis provoked by noxious stimuli, such as thoughts or smells, originates in the cerebral cortex. Cranial nerves are responsible for the gag reflex that results in emesis. Motion sickness and inner ear disorders act on the labyrinthine apparatus and vestibular system. Gastric irritants and anticancer medications that induce emesis stimulate the gastroduodenal vagal afferent nerves. Bowel obstruction or ischemia causes emesis through the stimulation of nongastric visceral afferent nerves. The chemoreceptor trigger zone in the medulla responds to blood-borne emetic stimuli. Neurotransmitters that induce emesis are selective for these anatomic sites. Labyrinthine disorders stimulate vestibular cholinergic muscarinic and histaminergic receptors. Gastroduodenal vagal afferent stimuli activate serotonin receptors. The chemoreceptor trigger zone has several receptor types, including serotonergic, cholinergic, histaminergic, and dopaminergic.

The differential diagnosis for nausea and vomiting is quite diverse. Conditions within and outside the gut as well as drugs and toxins can be responsible. Intraperitoneal disorders such as visceral obstruction and inflammation may produce vomiting. Gastric obstruction results from ulcer disease or cancer, whereas intestinal obstructions are typically due to adhesions, tumors, volvulus, intussusception, or inflammatory bowel disease such as Crohn's disease. The most common cause is duodenal ulcer disease, followed by functional dyspepsia and irritable bowel syndrome. Pregnancy is another common cause of temporary nausea and vomiting. Infectious and inflammatory diseases such as appendicitis, pancreatitis, and hepatitis can also cause nausea and vomiting. Rare metabolic diseases such as diabetic ketoacidosis, renal tubular acidosis, hypercalcemia, and adrenocortical insufficiency may also present with these symptoms. Drug-induced nausea should always be considered. Common offensive agents include nonsteroidal antiinflammatory drugs (NSAIDs), opiates, antibiotics, hormone preparations, and chemotherapeutic agents.

Obviously, different diseases can present with different symptoms, so diagnosis based upon gastrointestinal symptoms alone can be difficult. Other symptoms such as anorexia, weight loss, and abdominal pain must be taken into account. Temporal relations are also important clues to the underlying etiology. A detailed history and physical exam is key to finding the cause of nausea and vomiting. Symptoms must be identified as acute or chronic. Hematemesis, or vomiting blood, raises suspicion of ulcer disease, Mallory-Weiss tears, or malignancy. Feculent material in the vomit is present with more distal obstruction. Fevers suggest the presence of an infectious source. Headaches and visual changes may occur with an intracranial source.

Malignant disease is rare under the age of 45 years. It is reasonable to manage younger patients at initial presentation with trial medications and advice regarding lifestyle modification such as diet, weight reduction, smoking, and alcohol cessation. If symptoms persist, however, they should be evaluated further. Testing for H. pylori infection should be one of the first tests done to exclude infected duodenal ulcers. Patients over the age of 45 are likely to have organic pathology. Testing for H. pylori is less useful in this age group because it is very common, therefore, not specific. All patients aged over 45 with symptoms persisting more than four weeks should be referred for investigation.

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