• BACKGROUND
    • Infectious mononucleosis is typically a self-limited disease commonly affecting young adults. Splenic rupture is a rare but serious complication affecting 0.1% to 0.5% of patients with mononucleosis. Current guidelines (based on published case reports) recommend complete activity restriction for 3 weeks after onset of mononucleosis symptoms to reduce rupture risk. We examined actual timing of mononucleosis-associated splenic injury using a large repository of unpublished patient data.
  • HYPOTHESIS
    • The risk of splenic injury after infectious mononucleosis will remain elevated longer than previously estimated.
  • STUDY DESIGN
    • Retrospective case series.
  • LEVEL OF EVIDENCE
    • Level 4.
  • METHODS
    • The Military Health System Management Analysis and Reporting Tool (M2) was used to conduct a retrospective chart review. Coding records of TRICARE beneficiaries aged 5 to 65 years between 2006 and 2016 were screened. Patients diagnosed with both splenic injury and mononucleosis-like symptoms were identified, and their medical records were reviewed for laboratory confirmation of infection and radiographically evident splenic injury.
  • RESULTS
    • A total of 826 records of splenic injury were found in M2. Of these, 42 cases met the study criteria. Mean time to splenic injury was 15.4 (±13.5) days. Only 73.8% (n = 31) of injuries occurred within 21 days, and 90.5% (n = 38) of splenic injuries occurred within 31 days of symptom onset.
  • CONCLUSION
    • A substantial number of splenic injuries occur between 21 and 31 days after symptom onset. While most splenic injuries were atraumatic, consideration should be given to extending return-to-play guidelines to 31 days after symptom onset to minimize risk. Risk of chronic pain after splenic injury may be higher than previously believed.
  • CLINICAL RELEVANCE
    • The risk for postmononucleosis splenic injuries remains elevated longer than current guidelines suggest. Restricting activity for 31 days after mononucleosis symptom onset may reduce the risk of splenic injury.