What are the causes, evaluation, and treatment for green vomitus in an adult?

Green Vomiting in Adults: Urgent Evaluation for Bowel Obstruction

Green (bilious) vomiting in adults is a red flag symptom that mandates urgent evaluation for mechanical bowel obstruction, particularly small bowel obstruction or gastric outlet obstruction, which can lead to bowel ischemia, perforation, and death if not promptly diagnosed and treated.

Immediate Clinical Significance

Green or bilious vomitus indicates the presence of bile, which suggests that intestinal contents are being regurgitated proximally. This occurs when there is:

• Mechanical obstruction distal to the ampulla of Vater
• Gastric outlet obstruction from malignancy, stricture, or other causes
• Small bowel obstruction from adhesions, hernias, or tumors

The color comes from bile pigments (biliverdin), distinguishing it from other causes of vomiting.

Urgent Diagnostic Approach

Key Historical Elements to Obtain Immediately:

• Timing and progression: Sudden vs. gradual onset; frequency and volume
• Associated symptoms: Abdominal pain (colicky suggests obstruction), distension, inability to pass gas or stool (obstipation)
• Surgical history: Prior abdominal surgeries increase risk of adhesive small bowel obstruction
• Cancer history: Known malignancy raises concern for malignant obstruction 1
• Recent medication changes: Opioids can cause severe constipation and pseudo-obstruction

Critical Physical Examination Findings:

• Abdominal distension and tympany
• High-pitched or absent bowel sounds (hyperactive early, absent late in obstruction)
• Peritoneal signs: Rigidity, rebound tenderness suggest perforation or ischemia
• Hernias: Examine all hernia sites (inguinal, femoral, umbilical, incisional)
• Hydration status: Assess for hypovolemia from fluid sequestration

Immediate Laboratory and Imaging:

• Electrolytes: Check for hypokalemia, metabolic alkalosis from vomiting
• Lactate: Elevated suggests bowel ischemia
• Complete blood count: Leukocytosis may indicate ischemia or perforation
• Plain abdominal radiographs (upright and supine): Look for dilated bowel loops, air-fluid levels, free air
• CT abdomen/pelvis with IV contrast is the gold standard: Identifies level and cause of obstruction, assesses bowel viability 1

Management Algorithm

If Mechanical Obstruction Confirmed:

1. Immediate resuscitation:

   • NPO (nothing by mouth)
   • IV fluid resuscitation with normal saline, correct electrolytes (especially potassium) 2
   • Nasogastric tube decompression to prevent aspiration and reduce distension 1

2. Surgical consultation: Urgent for complete obstruction, peritoneal signs, or concern for ischemia

3. Antiemetics (after decompression initiated):

   • Ondansetron 4-8 mg IV (5-HT3 antagonist) 2
   • Metoclopramide should be AVOIDED in mechanical obstruction as it increases motility and can worsen obstruction 2

If Malignant Obstruction (Non-Surgical Candidate):

For patients with advanced cancer and poor prognosis 1:

• Endoscopic stent placement for gastric outlet obstruction (preferred if life expectancy <6 months)
• Venting gastrostomy if stenting not feasible
• Octreotide to reduce secretions
• Corticosteroids to reduce tumor-associated edema

If No Obstruction Found:

Consider alternative diagnoses requiring specific evaluation:

1. Gastroparesis 3:

   • Obtain gastric emptying scintigraphy (4-hour study)
   • Check HbA1c if diabetic
   • Trial of metoclopramide 10 mg PO/IV TID or domperidone (if available)
   • Dietary modification: small, frequent, low-fat meals

2. Cyclic Vomiting Syndrome 4, 5:

   • Stereotypical episodes with symptom-free intervals
   • Screen for cannabis use (cannabinoid hyperemesis syndrome) 6
   • Prophylaxis: Amitriptyline 25-50 mg nightly (first-line) 5
   • Acute treatment: Ondansetron 8 mg IV + sumatriptan 6 mg SC 5

3. Cannabinoid Hyperemesis Syndrome 6:

   • Daily/heavy cannabis use (>1 year, ≥4 times weekly)
   • Compulsive hot water bathing behavior
   • Cannabis cessation is definitive treatment (6 months to confirm diagnosis)
   • Supportive care with IV fluids, ondansetron

Critical Pitfalls to Avoid

• Never dismiss bilious vomiting as "gastroenteritis" without imaging—56% of surgical obstructions have normal initial plain films 7
• Do not use metoclopramide or other prokinetics if obstruction suspected—can cause perforation 2
• Do not delay imaging for "conservative management"—bowel ischemia develops rapidly
• Avoid antimotility agents (loperamide) which can precipitate toxic megacolon if inflammatory cause 8

When to Hospitalize

Admit all patients with bilious vomiting until obstruction is excluded, especially if:

• Unable to tolerate oral intake
• Electrolyte abnormalities
• Imaging shows any degree of obstruction
• Hemodynamic instability
• Severe pain or peritoneal signs

The mortality and morbidity from missed bowel obstruction far outweigh the costs of admission and imaging. Green vomiting is never "just a virus" until proven otherwise with definitive imaging.