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Nausea is a vague, intensely disagreeable sensation of sickness or “queasiness” and is distinguished from anorexia. Vomiting often follows, as does retching (spasmodic respiratory and abdominal movements). Vomiting should be distinguished from regurgitation, the effortless reflux of liquid or food stomach contents; and from rumination, the chewing and swallowing of food that is regurgitated volitionally after meals.

The brainstem vomiting center is composed of a group of neuronal areas (area postrema, nucleus tractus solitarius, and central pattern generator) within the medulla that coordinate emesis. It may be stimulated by four sources of afferent input: (1) Afferent vagal fibers from the GI viscera are rich in serotonin 5-HT3 receptors; these may be stimulated by biliary or GI distention, mucosal or peritoneal irritation, or infections. (2) Fibers of the vestibular system, which have high concentrations of histamine H1 and muscarinic cholinergic receptors. (3) Higher CNS centers (amygdala); here, certain sights, smells, or emotional experiences may induce vomiting. For example, patients receiving chemotherapy may start vomiting in anticipation of its administration. (4) The chemoreceptor trigger zone, located outside the blood-brain barrier in the area postrema of the medulla, is rich in opioid, serotonin 5-HT3, neurokinin 1 (NK1), and dopamine D2 receptors. This region may be stimulated by drugs and chemotherapeutic agents, toxins, hypoxia, uremia, acidosis, and radiation therapy. Although the causes of nausea and vomiting are many, a simplified list is provided in Table 15–1.

Table 15–1.Causes of nausea and vomiting.

CLINICAL FINDINGS

A. Symptoms and Signs

Acute symptoms without abdominal pain are typically caused by food poisoning, infectious gastroenteritis, drugs, or systemic illness. A 2021 prospective study of 1992 consecutive ...

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