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INTRODUCTION AND EPIDEMIOLOGY

Nausea and vomiting accompany a variety of illnesses. Symptoms may be due to primary GI disorders such as bowel obstruction or gastroenteritis. However, symptoms may also represent pathology of the CNS (increased intracranial pressure, tumor), psychiatric conditions (bulimia nervosa, anxiety), endocrine or metabolic abnormalities (DKA, hyponatremia), or iatrogenic causes (medications, toxins). Also, nausea and vomiting may be the result of severe pain, myocardial infarction, sepsis, or other systemic illnesses. A comprehensive history and physical examination, as well as the use of various diagnostic modalities, are needed to determine the cause and its complications.

In the United States, the most common cause of acute nausea and vomiting is viral gastroenteritis. Other important considerations are side effects from medication and, in young women, pregnancy.1

PATHOPHYSIOLOGY

Multiple neurons in the medulla oblongata are activated in a sequential fashion to induce vomiting. The vomiting center is the chemoreceptor trigger zone, located in the area postrema of the fourth ventricle. Chemoreceptors in this area are outside the blood–brain barrier and are stimulated by circulating medications and toxins, including dopaminergic antagonists (levodopa, bromocriptine), nicotine, digoxin, and opiate analgesics. Another important peripheral pathway for emesis is mediated through vagal afferents. Vagal activation is triggered by direct gastric mucosal irritants (such as NSAIDs) or increased luminal distention (gastric outlet obstruction, gastroparesis). Vagus activation stimulates neurons in the area postrema and nucleus tractus solitarius. These areas are rich in serotonin receptors and are a major site of action of antiemetic drugs, such as granisetron and odansetron.2 Similar receptors are found throughout the GI tract, as well as the cortex and limbic system, vestibular system, heart, and genitalia.

CLINICAL FEATURES

The differential diagnosis of nausea and vomiting is exhaustive, as pathology of almost every organ system may lead to nausea and vomiting (Table 72-1). A thorough history and physical examination will help guide the diagnostic approach to the patient presenting with nausea and vomiting.

TABLE 72-1Differential Diagnosis of Nausea and Vomiting

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