What causes prolonged vomiting for several weeks after a diagnosis of infectious mononucleosis (mono)?

Prolonged Vomiting After Infectious Mononucleosis

Vomiting persisting for several weeks after mono is most likely caused by post-infectious gastroparesis, EBV-related hepatitis with ongoing inflammation, or a secondary complication such as splenic enlargement causing gastric compression, rather than the acute infection itself. 1, 2

Primary Considerations

Post-Infectious Gastrointestinal Dysfunction

• EBV-associated mononucleosis can cause hepatitis that may persist beyond the acute phase, leading to ongoing nausea and vomiting through hepatic inflammation and metabolic disturbances 1, 2
• Massive splenomegaly, which occurs commonly in infectious mononucleosis, can cause mechanical gastric compression and delayed gastric emptying 3, 2
• Post-viral gastroparesis may develop after the acute infection resolves, causing persistent symptoms 4

Metabolic and Electrolyte Complications

• Prolonged vomiting causes hypokalemia, hypochloremia, and metabolic alkalosis that perpetuate the vomiting cycle 4
• EBV hepatitis can cause metabolic derangements including hypoglycemia and electrolyte abnormalities 1, 3

Rare Hematologic Complications

• Agranulocytosis can occur even weeks after acute EBV infection and may present with severe intoxication, fever, and gastrointestinal symptoms including vomiting 3
• Autoimmune hemolytic anemia and thrombocytopenia are relatively rare but documented complications that can cause systemic symptoms 3, 2

Diagnostic Approach

Initial Laboratory Evaluation

• Obtain complete blood count, serum electrolytes, glucose, liver function tests, lipase, and urinalysis to exclude metabolic causes and assess for dehydration 4
• Check for hypercalcemia, hypothyroidism, and adrenal insufficiency if clinically indicated 4
• Monitor for persistent hepatitis with elevated transaminases and bilirubin 1, 3

Imaging and Endoscopy

• Perform one-time esophagogastroduodenoscopy or upper GI imaging to exclude obstructive lesions, peptic ulcer disease, or malignancy 5, 4
• Consider gastric emptying scintigraphy if gastroparesis is suspected (requires 2-4 hour study) 5
• Abdominal ultrasound to assess spleen size and hepatic abnormalities 3

Rule Out Alternative Diagnoses

• Obtain urine drug screen to assess for cannabis use, as Cannabis Hyperemesis Syndrome can present similarly in this age group 4
• Consider CMV, Toxoplasma gondii, viral hepatitis, or HIV if EBV serologies are atypical 1, 6

Management Strategy

Immediate Supportive Care

• Correct electrolyte abnormalities, particularly hypokalemia and hypomagnesemia 4
• Ensure adequate fluid intake of at least 1.5 L/day with small, frequent meals 4
• Provide thiamin supplementation to prevent Wernicke's encephalopathy in patients with persistent vomiting 4

Pharmacologic Treatment

• Initiate dopamine receptor antagonists (metoclopramide, prochlorperazine, or haloperidol) titrated to maximum benefit and tolerance 4
• Add 5-HT3 antagonist such as ondansetron 4-8 mg if symptoms persist after 4 weeks, though monitor for QTc prolongation 5, 4
• Caution: Ondansetron may increase stool volume/diarrhea, which could be problematic if gastrointestinal symptoms are prominent 4
• If gastroparesis or gastritis is suspected, add proton pump inhibitor and continue metoclopramide as it promotes gastric emptying 4

Specific Complications Requiring Intervention

• If agranulocytosis is identified (absolute granulocyte count <0.5 x 10⁹/L), consider high-dose corticosteroids and filgrastim (G-CSF) 5 micrograms every other day 3
• Corticosteroids are indicated for autoimmune hemolytic anemia and thrombocytopenia if present 3, 2

Critical Pitfalls to Avoid

• Never use antiemetics in suspected mechanical bowel obstruction, as bilious vomiting requires urgent fluoroscopy upper GI series and surgical consultation 5, 4
• Do not perform repeated endoscopy or imaging unless new symptoms develop 4
• Monitor for extrapyramidal symptoms with dopamine antagonists, particularly in young patients 4
• Avoid overlooking medication causes if the patient was started on antibiotics or other drugs during acute illness 5
• Do not dismiss the possibility of rare hematologic complications, as agranulocytosis can occur even weeks to a year after acute EBV infection 3