Chapter 039. Nausea, Vomiting, and Indigestion (Part 4)

Diagnostic TestingFor intractable symptoms or an elusive diagnosis, selected diagnostic tests can direct clinical management. Electrolyte replenishment is indicated for hypokalemia or metabolic alkalosis. Detection of iron-deficiency anemia mandates a search for mucosal injury. Pancreaticobiliary disease is indicated by abnormal pancreatic enzymes or liver biochemistries, whereas endocrinologic,rheumatologic, or paraneoplastic etiologies are suggested by specific hormone or serologic testing. If luminal obstruction is suspected, supine and upright abdominal radiographs may show intestinal air-fluid levels with reduced colonic air. Ileus is characterized by diffusely dilated air-filled bowel loops. ...
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Chapter 039. Nausea, Vomiting, and Indigestion (Part 4) Chapter 039. Nausea, Vomiting, and Indigestion (Part 4) Diagnostic Testing For intractable symptoms or an elusive diagnosis, selected diagnostic testscan direct clinical management. Electrolyte replenishment is indicated forhypokalemia or metabolic alkalosis. Detection of iron-deficiency anemia mandatesa search for mucosal injury. Pancreaticobiliary disease is indicated by abnormalpancreatic enzymes or liver biochemistries, whereas endocrinologic,rheumatologic, or paraneoplastic etiologies are suggested by specific hormone orserologic testing. If luminal obstruction is suspected, supine and uprightabdominal radiographs may show intestinal air-fluid levels with reduced colonicair. Ileus is characterized by diffusely dilated air-filled bowel loops. Anatomic studies may be indicated if initial testing is nondiagnostic. Upperendoscopy detects ulcers or malignancy, while small-bowel barium radiographydiagnoses partial small-bowel obstruction. Colonoscopy or contrast enemaradiography can detect colonic obstruction. Abdominal ultrasound or computedtomography (CT) defines intraperitoneal inflammatory processes, while CT ormagnetic resonance imaging (MRI) of the head can delineate intracranial disease.Mesenteric angiography or MRI is useful when ischemia is considered. Gastrointestinal motility testing may detect a motor disorder thatcontributes to symptoms when anatomic abnormalities are absent. Gastroparesiscommonly is diagnosed using gastric scintigraphy, by which emptying of aradiolabeled meal is measured. Isotopic breath tests and telemetry capsulemethods also have been validated. Electrogastrography, a noninvasive test ofgastric slow-wave activity using cutaneous electrodes placed over the stomach,has been proposed as an alternate means of diagnosing gastroparesis. Thediagnosis of intestinal pseudoobstruction often is suggested by abnormal bariumtransit and luminal dilation on small-bowel contrast radiography. Small-intestinalmanometry can confirm the diagnosis and further characterize the motorabnormality as neuropathic or myopathic based on contractile patterns. Suchinvestigation can obviate the need for open intestinal biopsy to evaluate forsmooth muscle or neuronal degeneration. Nausea and Vomiting: Treatment General Principles Therapy of vomiting is tailored to correction of medically or surgicallyremediable abnormalities if possible. Hospitalization is considered for severedehydration especially if oral fluid replenishment cannot be sustained. Once oralintake is tolerated, nutrients are restarted with liquids that are low in fat, as lipidsdelay gastric emptying. Foods high in indigestible residues are avoided as thesealso prolong gastric retention. Antiemetic Medications The most commonly used antiemetic agents act on sites within the centralnervous system (Table 39-2). Antihistamines such as meclizine anddimenhydrinate and anticholinergic drugs like scopolamine act on labyrinthine-activated pathways and are useful in motion sickness and inner ear disorders.Dopamine D2 antagonists treat emesis evoked by area postrema stimuli and areuseful for medication, toxic, and metabolic etiologies. Dopamine antagonistsfreely cross the blood-brain barrier and cause anxiety, dystonic reactions,hyperprolactinemic effects (galactorrhea and sexual dysfunction), and irreversibletardive dyskinesia. Table 39-2 Treatment of Nausea and Vomiting Treatm Mechanism Examples Clinicalent Indications Antieme Antihistamine Dimenhydrinate, Motiontic agents rgic meclizine sickness, inner ear disease Anticholinergi Scopolamine Motion c sickness, inner ear disease Antidopamine Prochlorperazine, Medication-, rgic thiethylperazine toxin-, or metabolic-induced emesis 5-HT3 Ondansetron, Chemothera antagonist granisetron py- and radiation- ...