Structural studies

Structural investigation may be needed to exclude organic illness as a cause of vomiting. Flat and upright abdominal radiographs are obtained as a screening examination. Small intestinal air–fluid levels with absent colonic air suggest obstruction, whereas diffuse distension is consistent with ileus. Contrast radiography of the small intestine may confirm partial obstruction. If symptoms are intermittent, enteroclysis may provide more detailed assessment of the small bowel. Upper endoscopy can assess possible gastric outlet obstruction and affords the ability to perform biopsy of suspicious lesions. Retained food in the absence of obstruction is seen in gastroparesis. For suspected pancreaticobiliary disease, ultrasound, computed tomography (CT), endoscopic ultrasound, hepatobiliary scintigraphy, or magnetic resonance cholangiopancreatography may be useful. Computed tomographic and magnetic resonance imaging (MRI) of the head may be indicated for suspected central nervous system sources. Angiography or MRI can detect mesenteric ischemia.

Functional studies

When lumenal obstruction is excluded, gastroparesis and intestinal pseudo-obstruction are considered causes of symptoms. Gastroparesis is diagnosed by demonstrating delayed emptying of an ingested meal. Scintigraphic measures of emptying of solid (^99mTc-sulfur colloid in eggs) or liquid (¹¹¹In-DTPA in water) radionuclides are most commonly used, although office-based breath tests using ¹³C-labeled foods show promise.

When scintigraphy incompletely characterizes the cause of nausea and vomiting, other functional tests may be offered in specialized gastrointestinal physiology laboratories. Manometry of the stomach and duodenum can evaluate motor patterns under fasting and fed conditions. These patterns are reasonably specific for neuropathic and myopathic causes of gastroparesis and pseudo-obstruction. Intestinal manometry complements findings from barium radiography of the small intestine, which can reveal slow transit and lumenal dilation in cases of severe dysmotility. Electrogastrography measures electrical pacemaker activity of the stomach through electrodes affixed to the abdomen. Some clinical conditions produce pacemaker rhythms that are too rapid (tachygastria) or slow (bradygastria) that are postulated to underlie development of nausea and vomiting. In rare cases of severe unexplained dysmotility, a surgical full-thickness intestinal biopsy is required to show degeneration of nerve or muscle layers.

Differential diagnosis

Nausea is the subjective sensation of an impending urge to vomit, and vomiting (emesis) is the forceful ejection of gastric contents from the mouth. Retching may precede vomiting but involves no discharge of upper gut contents. Other symptoms may be misinterpreted by the patient as nausea or vomiting. Regurgitation is the effortless return of gastric or esophageal contents in the absence of nausea or involuntary spasmodic muscular contractions. Rumination is characterized by regurgitation of food into the mouth, where it is rechewed and reswallowed. Anorexia refers to loss of appetite. Early satiety is the sensation of gastric fullness before a meal is completed. Nausea may be part of a general complaint of indigestion that includes abdominal discomfort, heartburn, anorexia, and bloating. The differential diagnosis of nausea and vomiting includes medications, gastrointestinal and intraperitoneal disease, neurological disorders, metabolic conditions, and infections (Table 5.1).

Medications

Drug reactions are among the most common causes of nausea and vomiting, especially within days after initiating therapy. Chemotherapeutic agents such as cisplatin and cyclophosphamide are potent emetic stimuli that act on central and peripheral neural pathways. Emesis from chemotherapy may be acute, delayed, or anticipatory. Analgesics such as aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) induce nausea by direct gastrointestinal mucosal irritation. Other classes of medications that produce nausea include cardiovascular drugs (e.g. digoxin, antiarrhythmics, antihypertensives), diuretics, hormonal agents (e.g. oral antidiabetics, contraceptives), antibiotics (e.g. erythromycin), and gastrointestinal medications (e.g. sulfasalazine).

Table 5.1 Causes of nausea and vomiting

Medications
Nonsteroidal anti-inflammatory drugs
Cardiovascular drugs (e.g. digoxin, antiarrhythmics, antihypertensives)
Diuretics
Hormonal agents (e.g. oral antidiabetics, contraceptives)
Antibiotics (e.g. erythromycin)
Gastrointestinal drugs (e.g. sulfasalazine)

Central nervous system disorders
Tumors
Cerebrovascular accident
Intracranial hemorrhage
Infections
Congenital abnormalities
Psychiatric disease (e.g. anxiety, depression, anorexia nervosa, bulimia nervosa, psychogenic vomiting)
Motion sickness
Labyrinthine causes (e.g. tumors, labyrinthitis, Ménière disease)

Miscellaneous causes
Posterior myocardial infarction
Congestive heart failure
Excess ethanol ingestion
Jamaican vomiting sickness
Prolonged starvation
Cyclic vomiting syndrome
Chronic cannabis use (cannabinoid hyperemesis syndrome)

Gastrointestinal and peritoneal disorders
Gastric outlet obstruction
Obstruction of the small intestine
Superior mesenteric artery syndrome
Gastroparesis
Chronic intestinal pseudo-obstruction
Pancreatitis
Appendicitis
Cholecystitis
Acute hepatitis
Pancreatic carcinoma

Endocrinological and metabolic conditions
Nausea of pregnancy
Uremia
Diabetic ketoacidosis
Thyroid disease
Addison disease

Infectious disease
Viral gastroenteritis (e.g. Hawaii agent, rotavirus, reovirus, adenovirus, Snow Mountain agent, Norwalk agent)
Bacterial causes (e.g. Staphylococcus spp., Salmonella spp., Bacillus cereus, Clostridium perfringens)
Opportunistic infection (e.g. cytomegalovirus, herpes simplex virus)
Otitis media