Infectious mononucleosis (mono), often caused by the Epstein-Barr virus (EBV), is a widespread viral illness. While the infection is usually self-limiting, causing symptoms like fever, fatigue, and sore throat, it carries a small but serious risk of complications. The primary concern is the effect the virus has on the spleen, which can lead to a life-threatening event. This article assesses the risk of splenic injury associated with mono and the necessary steps to prevent it.
The Link Between Mono and Spleen Enlargement
The spleen, located in the upper left abdomen, filters blood and stores immune cells. During an acute EBV infection, the body mounts a robust immune response, generating large numbers of immune cells to fight the virus. These cells accumulate within the spleen, causing the organ to swell, a condition known as splenomegaly.
This intense cellular infiltration increases pressure within the organ’s capsule, the thin membrane surrounding the spleen. The enlargement stretches this capsule, making the spleen fragile and highly susceptible to injury. Splenomegaly is found in up to half of patients with active mononucleosis. The spleen’s fragile, enlarged state means that even minor trauma or increased abdominal pressure can result in a tear or rupture.
Quantifying the Risk of Splenic Rupture
Splenic rupture is a very rare complication, occurring in an estimated 0.1% to 0.5% of all mononucleosis cases. The vast majority of individuals who contract mono will not experience this complication.
The highest vulnerability occurs during the first few weeks after symptoms begin. The mean time from the onset of symptoms to a splenic injury is around 15.4 days. Most injuries occur within the first 21 days, but ruptures have been documented up to 31 days after symptom onset.
Splenic rupture is almost always associated with trauma, though the trauma may be minor. A large percentage of ruptures are classified as atraumatic, meaning they occur without a clear, forceful impact. This can include seemingly innocuous actions like straining or coughing. The risk remains elevated until the spleen returns to its normal size, which often takes four weeks or longer, and sometimes up to eight weeks.
Necessary Activity Restrictions During Mono Recovery
Temporary activity restrictions are required during recovery to mitigate the risk of splenic rupture. Restrictions focus on avoiding any activity that could cause direct abdominal trauma or significantly increase intra-abdominal pressure.
The most dangerous activities include all contact sports (football, basketball, hockey, and wrestling) due to the high risk of blunt force impact to the torso. Strenuous activities involving lifting, pushing, or straining must also be avoided, as these actions sharply elevate pressure within the abdominal cavity.
Prohibited activities include heavy weightlifting, intense calisthenics, and vigorous labor. Light, non-strenuous activities, such as short walks, are generally acceptable if the patient feels well.
The standard recommendation for avoiding contact sports is a minimum of three to four weeks, though some data suggests a restriction period of 31 days or up to eight weeks. Normal activity should not be resumed until the spleen is confirmed to be no longer enlarged. Confirmation often requires a physician’s physical exam or an abdominal ultrasound. Returning to activity too early is the primary preventable cause of this serious complication.
Recognizing the Signs of a Ruptured Spleen
Recognizing the signs of an acute splenic rupture is important, as it constitutes a medical emergency requiring immediate attention. The most common symptom is the sudden onset of severe, sharp pain, typically localized in the upper left side of the abdomen. This pain is often intense and quickly worsens.
A specific indicator of internal bleeding is pain felt in the left shoulder, known as Kehr’s sign. This referred pain occurs because the blood irritates the diaphragm, which shares nerve connections with the shoulder area. Kehr’s sign is a strong indicator but is not always present.
As internal bleeding progresses, patients may quickly develop signs of shock due to significant blood loss. Systemic symptoms include lightheadedness, dizziness, a rapid heart rate, and confusion or fainting. If sudden, severe abdominal pain combined with signs of internal bleeding occurs during a mono infection, emergency medical help must be sought immediately.