Is an ultrasound of the abdomen mandatory for patients with minor symptoms of infectious mononucleosis?

Management of Infectious Mononucleosis: Abdominal Ultrasound is NOT Mandatory for Minor Symptoms

Routine abdominal ultrasound is not required for patients with infectious mononucleosis who have minor symptoms and no specific abdominal complaints. 1

Clinical Assessment Should Guide Imaging Decisions

The decision to perform abdominal imaging in infectious mononucleosis should be based on specific clinical indicators rather than routine screening:

When Ultrasound is NOT Indicated

• Patients with typical IM symptoms alone (fever, pharyngitis, lymphadenopathy, fatigue) without abdominal complaints do not require routine ultrasound 1
• Mildly elevated liver function tests without clinical symptoms do not necessitate abdominal imaging in immunocompetent patients 1
• Routine screening for splenomegaly in asymptomatic patients is not evidence-based 1

When Ultrasound IS Indicated

Abdominal ultrasound becomes mandatory when specific warning signs are present:

• Left upper quadrant or hypochondrial pain - this is rare in uncomplicated IM and should raise concern for splenic complications 2
• Kehr's sign (left shoulder pain) - suggests diaphragmatic irritation from splenic bleeding 2
• Signs of peritoneal irritation - abdominal rigidity or guarding 2
• Hemodynamic instability - hypotension, tachycardia, or signs of acute blood loss 2
• Progressive anemia - unexplained drop in hemoglobin 2

The Evidence Against Routine Imaging

A systematic review of 3,924 patients with infectious mononucleosis found that:

• Clinical hepatomegaly occurred in 35% and splenomegaly in 44% of patients 1
• Ultrasound detected enlarged organs but did not change management in patients without specific symptoms 1
• No cases of decompensated liver disease were reported despite abnormal liver function tests 1
• Current evidence questions the need for routine LFT assessment in immunocompetent patients, let alone routine imaging 1

Understanding Splenic Rupture Risk

While splenic rupture is the most feared complication, it remains rare:

• Occurs in only 0.1-0.5% of IM cases 3
• Mortality rate is approximately 30% when rupture occurs 2
• Most ruptures present with clear symptoms - not as incidental findings on screening ultrasound 4, 2
• Spontaneous rupture without trauma is extremely rare - only 18 well-documented cases in the literature 4

Practical Management Algorithm

For patients with minor symptoms (fatigue, sore throat, fever, lymphadenopathy):

• Clinical examination is sufficient 3, 5
• No imaging required 1
• Advise avoidance of contact sports for 8 weeks 3, 5

For patients with abdominal pain:

• Urgent ultrasound or CT is mandatory 2
• This approach is critical when pain is associated with referred shoulder pain, peritoneal signs, or hemodynamic changes 2

For patients with deranged liver function tests but no symptoms:

• Routine ultrasound is not required 1
• Serial LFT monitoring is also unnecessary in immunocompetent patients 1

Important Clinical Pitfalls to Avoid

• Do not order routine imaging "just to check the spleen" - this is not supported by evidence and exposes patients to unnecessary healthcare costs 1
• Do not ignore new-onset abdominal pain - this requires immediate imaging as it may herald splenic rupture 2
• Do not rely on the absence of trauma history - spontaneous rupture can occur, though rarely 4, 2
• Do not allow patients to return to contact sports before 8 weeks regardless of how well they feel, as rupture risk persists after clinical recovery 4, 5

The Bottom Line

Reserve abdominal ultrasound for patients with specific abdominal symptoms or signs suggesting complications. The vast majority of IM patients with minor symptoms require only supportive care and activity restriction, not imaging surveillance. Clinical judgment based on symptomatology - not routine screening protocols - should drive imaging decisions in infectious mononucleosis.