How should I evaluate and manage a patient who presents with vomiting, including history, physical exam, laboratory studies, imaging, and initial treatment?

Workup for Vomiting: A Structured Clinical Approach

Begin with a focused history targeting timing, characteristics, and red-flag features, followed by immediate basic laboratory testing (complete blood count, comprehensive metabolic panel, liver function tests, lipase, and urinalysis) to identify life-threatening causes and guide further evaluation. 1

Initial History: Critical Features to Elicit

Timing and onset pattern:

• Vomiting within first 2 days of life with bilious emesis or failure to pass meconium suggests bowel obstruction requiring urgent surgical evaluation—20% have midgut volvulus 2
• Morning symptoms in reproductive-age females indicate pregnancy until proven otherwise 3
• Postprandial symptoms suggest gastroparesis or functional dyspepsia 3

Vomitus characteristics:

• Bilious vomiting is an ominous sign requiring immediate imaging to exclude malrotation with volvulus 2, 1
• Undigested food suggests gastroparesis 3
• Blood indicates mucosal injury from Mallory-Weiss tear, ulcer, or malignancy 2

Associated symptoms requiring immediate attention:

• Altered sensorium, severe headache, or neurologic signs mandate head CT to exclude intracranial pathology 1, 4
• Abdominal distension with bilious vomiting indicates bowel obstruction 3, 4
• Severe dehydration (orthostatic hypotension, decreased skin turgor, dry mucous membranes) requires aggressive fluid resuscitation 2, 4

Epidemiologic and medication history:

• Cannabis use (≥4 times weekly for >1 year) suggests Cannabis Hyperemesis Syndrome—obtain non-judgmental substance history 2, 1
• Recent antibiotics, chemotherapy, or opiates are common culprits 2, 5
• Digoxin, phenytoin, carbamazepine toxicity can precipitate vomiting 1

Physical Examination: Key Findings

Volume status assessment:

• Check orthostatic vital signs, mucous membrane moisture, skin turgor, and jugular venous pulsations 2
• Tachycardia and orthostasis indicate significant dehydration requiring IV fluids 2

Abdominal examination:

• Distension with bilious vomiting mandates immediate surgical consultation 4
• Peritoneal signs suggest perforation, appendicitis, or other surgical emergency 4

Specific physical findings:

• Parotid gland enlargement (swollen cheeks/jawline) is pathognomonic for bulimia nervosa 6
• Neurologic deficits require head imaging 1, 4
• In infants: bulging fontanelle, enlarging head circumference suggest increased intracranial pressure 2

Initial Laboratory Testing (Mandatory for All Patients)

First-line panel:

• Complete blood count to identify infection, anemia, or hematologic abnormalities 1
• Comprehensive metabolic panel (electrolytes, glucose, BUN, creatinine) to detect hypokalemia, hypochloremia, metabolic alkalosis, and assess dehydration severity 1
• Liver function tests (AST, ALT, bilirubin) to evaluate hepatobiliary pathology 1
• Serum lipase to screen for acute pancreatitis 1
• Urinalysis to detect urinary tract infection, ketonuria, or renal disease 1

Additional testing based on clinical context:

• Urine pregnancy test immediately in all reproductive-age females—pregnancy is the most common cause in this demographic 3
• Urine drug screen in adolescents/young adults to detect cannabis or other substances 1
• Thyroid-stimulating hormone if hypothyroidism suspected 1
• Morning cortisol or ACTH stimulation test if Addison's disease suspected (unexplained hypotension, hyperpigmentation, hyponatremia) 1
• Serum calcium if hypercalcemia suspected 1

Critical pitfall: Hypokalemia and hypochloremic metabolic alkalosis strongly suggest purging behaviors in bulimia nervosa—obtain ECG to assess QTc prolongation and risk of sudden cardiac death 6

Imaging Studies: When and What to Order

Abdominal radiography:

• First-line imaging for suspected bowel obstruction—can differentiate proximal versus distal obstruction patterns 2
• Normal radiographs do NOT exclude malrotation—only 44% of surgical cases had definitively positive readings 2

Upper GI series with small bowel follow-through:

• Reference standard for evaluating malrotation in infants/children with bilious vomiting 2
• Sensitivity 96% but false-positives occur (10-15%) due to redundant duodenum or bowel distension 2
• Do NOT delay this study when bilious vomiting is present—midgut volvulus is a surgical emergency 1

Abdominal ultrasound:

• Limited role as primary modality for malrotation (21% false-positive, 2-3% false-negative for SMV/SMA relationship) 2
• Whirlpool sign (clockwise wrapping of SMV around SMA) is specific for midgut volvulus 2

Head CT/MRI:

• Indicated only when neurologic signs or symptoms of increased intracranial pressure present 1, 3

Avoid these imaging pitfalls:

• Do NOT perform contrast enema or upper GI series before plain abdominal radiograph 2
• Do NOT order gastric emptying scan routinely—few CVS patients have delayed emptying, and cannabis/opiate use confounds interpretation 2
• Do NOT repeat endoscopy or imaging unless new alarm symptoms develop 3

Advanced Diagnostic Testing (When Initial Workup Non-Diagnostic)

Upper endoscopy (EGD):

• Recommended when symptoms persist >7 days or worsen despite normal initial labs 1
• Excludes mechanical obstruction, peptic ulcer disease, malignancy 1
• One-time study is sufficient to exclude obstructive lesions—avoid repeated procedures 2

Gastric emptying scintigraphy:

• Gold standard for gastroparesis diagnosis—must run ≥2 hours (preferably 4 hours) with radiolabeled solid meal 3
• Consider when postprandial fullness, early satiety, and bloating predominate 3

Initial Treatment Priorities

Fluid resuscitation:

• Oral rehydration solution (Na 90 mM, K 20 mM, Cl 80 mM, HCO₃ 30 mM, glucose 111 mM) is superior to IV fluids for patients able to take oral fluids—less painful, safer, less costly 2
• IV fluids required for severe dehydration, altered mental status, or inability to tolerate oral intake 2, 4

Nasogastric decompression:

• Mandatory for bilious vomiting to decompress stomach before surgical evaluation 4

Antiemetic therapy:

• Ondansetron 8 mg sublingual every 4-6 hours for acute vomiting 2
• Critical warning: Obtain baseline ECG before ondansetron—drug prolongs QTc, especially with electrolyte abnormalities 2, 1
• Do NOT use antiemetics if mechanical bowel obstruction suspected—masks progressive ileus and gastric distension 3

Pregnancy-specific management:

• First-line: Ginger 250 mg four times daily and vitamin B₆ (pyridoxine) 10-25 mg every 8 hours 2
• Second-line: Doxylamine (H1-antagonist) FDA-approved for persistent nausea/vomiting of pregnancy 2
• Thiamine 100 mg daily for minimum 7 days to prevent Wernicke encephalopathy in hyperemesis gravidarum 2

Common Pitfalls to Avoid

• Never overlook pregnancy testing in reproductive-age females regardless of reported sexual history 3
• Never delay imaging when bilious vomiting present—malrotation with volvulus is life-threatening 1
• Never assume normal labs exclude serious illness—>50% of adolescents with eating disorders have normal results despite medical instability 6
• Never stigmatize cannabis users—obtain direct, non-judgmental substance history as Cannabis Hyperemesis Syndrome is increasingly common 2, 1
• Aggressively correct hypokalemia and hypomagnesemia to prevent worsening symptoms and cardiac complications 1