What is the appropriate workup and management for a patient with spleen pain due to infectious mononucleosis (mono)?

Workup for Spleen Pain Due to Infectious Mononucleosis

Obtain an abdominal CT scan with intravenous contrast immediately in any patient with infectious mononucleosis presenting with abdominal pain, as this is the gold standard for detecting splenic complications including rupture, infarction, or abscess, with 90-95% sensitivity and specificity. 1, 2

Initial Clinical Assessment

Key Physical Examination Findings

• Assess for left upper quadrant tenderness, referred left shoulder pain (Kehr's sign), and peritoneal signs, as 48% of mononucleosis patients develop abdominal pain and 24% present with abdominal complaints as their chief symptom 3
• Palpate carefully for splenomegaly, which occurs in approximately 50% of infectious mononucleosis cases, though clinical splenomegaly is present in only 30% of patients with actual splenic complications 4, 1
• Monitor hemodynamic status closely with serial vital signs, as splenic rupture can present with sudden fatal hemorrhage or more subtle bleeding that stops spontaneously 5

Laboratory Workup

• Obtain complete blood count with differential looking for leukocytosis with >50% lymphocytes and >10% atypical lymphocytes 4
• Measure serial hematocrit every 6 hours if splenic injury is suspected, as decreasing hematocrit indicates ongoing bleeding 1
• Confirm EBV infection with monospot test or, if negative, with viral capsid antigen (VCA) antibodies 4, 6

Imaging Strategy

Primary Imaging Modality

• CT scan with IV contrast is mandatory for any patient with abdominal pain and infectious mononucleosis, as it detects splenic rupture, subcapsular hematoma, infarction, and abscess 1, 2, 6
• CT findings to identify: Look for peripheral low-density wedge-shaped areas (infarction), contrast-enhancing cystic lesions (abscess), or free fluid with splenic laceration (rupture) 1

Alternative and Follow-up Imaging

• Doppler ultrasound or contrast-enhanced ultrasound can evaluate splenic vascularization and is useful for follow-up monitoring 1
• Repeat CT scanning at 36-72 hours should be considered in patients with decreasing hematocrit, moderate-to-severe injuries, or underlying splenic pathology 1

Risk Stratification and Timing

Critical Time Window

• Splenic rupture occurs in 0.1-0.5% of infectious mononucleosis cases, with mean time to injury of 15.4 days after symptom onset 4, 7
• Only 73.8% of ruptures occur within 21 days, and 90.5% occur within 31 days, meaning risk extends beyond traditional 3-week guidelines 7
• Delayed rupture can occur 4-10 days after initial presentation, with some cases reported months later 1

Management Based on Findings

If Imaging Shows Splenic Injury

• Grade I-II injuries (minor): Observe with bed rest for 48-72 hours, serial abdominal exams, and hematocrit monitoring every 6 hours 1
• Grade III-V injuries (moderate-severe): Consider hospital admission with close observation, potential angioembolization if hemodynamically stable with persistent bleeding, or immediate splenectomy if unstable 1
• Contained rupture with hemodynamic stability: Non-operative management is acceptable with intensive monitoring in a critical care setting with immediate operating room access 5, 6

If Imaging Shows Splenic Abscess

• Start broad-spectrum IV antibiotics immediately targeting Staphylococcus aureus and viridans streptococci (40% each in endocarditis-related cases) 2, 1
• Percutaneous catheter drainage is first-line for abscesses >4 cm with 80-90% success rates, preserving splenic function 2
• Proceed to splenectomy if percutaneous drainage fails, multiple complex abscesses exist, or persistent bacteremia continues despite antibiotics 2, 1

Activity Restriction Guidelines

Evidence-Based Recommendations

• Restrict all contact sports and strenuous exercise for minimum 31 days after symptom onset, as substantial splenic injuries occur between 21-31 days 7, 4
• Extend restriction to 8 weeks or until splenomegaly resolves documented by ultrasound or CT, as this provides additional safety margin 4, 5
• For documented splenic injury: Activity restriction of 4-6 weeks for minor injuries (Grade I-II) and 2-4 months for moderate-severe injuries (Grade III-V) 1

Post-Splenectomy Prophylaxis (If Surgery Required)

Vaccination Protocol

• Vaccinate at least 14 days post-operatively against Streptococcus pneumoniae, Haemophilus influenzae type b, and Neisseria meningitidis 8, 9
• Administer annual influenza vaccination for all post-splenectomy patients over 6 months of age 8, 9
• Reimmunize every 5-10 years for pneumococcal vaccine 9

Antibiotic Prophylaxis

• Initiate lifelong phenoxymethylpenicillin 250-500 mg twice daily, with highest priority in first 2 years post-splenectomy 8, 9
• Prescribe erythromycin for penicillin-allergic patients 8, 9
• Provide emergency standby amoxicillin (3g starting dose, then 1g every 8 hours) for home use at first sign of fever 8, 9

Patient Education

• Issue Medic-Alert identification and educate about lifelong OPSI risk with 30-70% mortality 8, 9
• Instruct immediate medical attention for any fever >101°F (38°C), malaise, or chills 9

Critical Pitfalls to Avoid

• Never rely on absence of splenomegaly to rule out splenic complications, as clinical examination is unreliable 1
• Do not discharge patients with persistent abdominal pain without CT imaging, as four young patients in Portland recently died at home from undiagnosed splenic rupture 3
• Avoid premature return to activity before 31 days or documented splenic healing, as current 21-day guidelines miss 26% of ruptures 7
• Do not treat large splenic abscesses (>4 cm) with antibiotics alone, as this has high failure rates and mortality from untreated sepsis 2