What are the possible causes of frequent vomiting immediately after eating and significant weight loss in a previously healthy 29-year-old?

Differential Diagnosis of Postprandial Vomiting with Significant Weight Loss in a Young Adult

Most Likely Diagnoses Requiring Urgent Evaluation

In a previously healthy 29-year-old with immediate postprandial vomiting for one year and 10kg weight loss over 2 months, the most critical diagnoses to exclude are mechanical gastric outlet obstruction, gastroparesis, and eating disorders—particularly bulimia nervosa—as these conditions directly cause the symptom pattern described and carry significant morbidity if untreated. 1, 2, 3

Mechanical Obstruction (Highest Priority)

• Upper endoscopy must be performed first to rule out mechanical obstruction before considering functional or motility disorders, as this is the essential initial step in the diagnostic algorithm 1, 4, 5
• Gastric outlet obstruction from peptic ulcer disease, malignancy, or pyloric stenosis can present with immediate postprandial vomiting and rapid weight loss 1
• Malignancy (gastric cancer, pancreatic cancer) must be excluded given the age, duration of symptoms, and severity of weight loss 1, 6

Gastroparesis

• Defined as delayed gastric emptying without mechanical obstruction, characterized by nausea, vomiting, early satiety, and postprandial fullness 2, 4, 5
• Gastric emptying scintigraphy is the gold standard diagnostic test and should be performed for at least 2 hours, preferably 4 hours, after ingestion of a radiolabeled meal 1, 4
• Common etiologies include diabetic (25% of cases), idiopathic (largest group), medication-induced (opioids, GLP-1 agonists), and post-surgical 2
• The timing of vomiting (immediately after eating) is somewhat atypical for gastroparesis alone, which usually presents with delayed vomiting 2, 7

Eating Disorders (Critical Consideration)

• Bulimia nervosa presents with recurrent binge eating followed by compensatory purging behaviors (self-induced vomiting) at least once weekly for 3 months, with self-worth overly based on body shape and weight 2, 3
• The pattern of vomiting "only when eating" and "immediately after eating" with significant weight loss (10kg in 2 months) is highly consistent with purging behavior 2, 3
• Self-induced vomiting can cause dental caries, salivary gland enlargement, gastroesophageal reflux disease, and electrolyte imbalances including potentially fatal hypokalemia 3
• Peak age of onset for bulimia nervosa is late adolescence to young adulthood, making this diagnosis age-appropriate 2

Essential Diagnostic Workup

Initial Laboratory Evaluation

• Complete blood count, serum electrolytes (particularly potassium), glucose, liver function tests, and lipase to rule out metabolic causes and assess for complications, with diagnostic yield of 70-80% 1, 6
• Urinalysis to evaluate hydration status and rule out renal causes 1
• For persistent vomiting >2-3 weeks, evaluate thiamin levels to prevent Wernicke encephalopathy 1, 4
• Check for hypokalemia and metabolic alkalosis, which suggest purging behaviors 3

Imaging and Endoscopic Evaluation

• Upper endoscopy (EGD) is mandatory as the first diagnostic test to exclude mechanical obstruction, malignancy, peptic ulcer disease, and assess for signs of self-induced vomiting (esophagitis, gastritis) 1, 4, 5
• If endoscopy is normal, proceed to gastric emptying scintigraphy using standardized low-fat egg white meal labeled with 99mTc sulfur colloid 4
• Medications affecting gastric emptying must be withdrawn 48-72 hours before testing 4

History Details to Elicit

• Detailed eating behaviors: timing of vomiting relative to meals, whether vomiting is effortless or forceful, presence of nausea before vomiting 1, 6
• Psychological factors: body image concerns, fear of weight gain, dietary restriction patterns, binge eating episodes 2, 3
• Medication and substance use: opioids, GLP-1 agonists, cannabis (cannabinoid hyperemesis syndrome), diet pills 2, 1, 5
• Associated symptoms: abdominal pain, early satiety, bloating, dental problems, hand calluses (Russell's sign from self-induced vomiting) 2, 3

Additional Differential Considerations

Cyclic Vomiting Syndrome

• Characterized by stereotypical episodes of nausea and vomiting with symptom-free intervals between episodes 5, 8
• The continuous nature of symptoms for one year makes this less likely unless episodes are frequent 5

Cannabinoid Hyperemesis Syndrome

• Requires history of long-term and intense cannabis use with characteristic pattern of cyclic vomiting and compulsive hot bathing 5
• Diagnosis requires cessation of cannabis for at least 6 months or 3 typical cycles 5

Superior Mesenteric Artery Syndrome

• Can occur with rapid weight loss and presents with postprandial vomiting 3
• More common in patients with eating disorders who have lost significant weight 3

Critical Pitfalls to Avoid

• Do not assume functional dyspepsia or gastroparesis without first excluding mechanical obstruction via endoscopy 1, 4
• Do not overlook eating disorders, particularly in young adults with weight loss and postprandial vomiting, as denial and concealment are common 2, 3
• Do not rely solely on patient-reported dietary intake; assess for signs of purging including dental erosion, parotid enlargement, and electrolyte abnormalities 3
• Do not perform gastric emptying studies before ruling out mechanical obstruction, as this wastes time and resources 1, 4
• Failure to check electrolytes can miss life-threatening hypokalemia from purging behaviors 3

Immediate Management Priorities

• Ensure adequate hydration with oral or intravenous fluids to prevent dehydration and electrolyte imbalances 1, 4
• Correct electrolyte abnormalities, particularly hypokalemia which carries risk of fatal arrhythmia 3
• Consider antiemetic therapy for symptom control while completing diagnostic evaluation 1
• Nutritional assessment is essential given 10kg weight loss in 2 months 1, 4
• If eating disorder is suspected, involve behavioral health specialists early in the evaluation 2, 3