Swine influenza (H1N1) and acute appendicitis.

Background: During the swine influenza (H1N1) pandemic that began in 2009, many hospitalized adults had gastrointestinal symptoms. The most common symptoms associated with swine influenza (H1N1) were nausea, vomiting, or diarrhea. In the experience of the authors, swine influenza was not complicated by abdominal pain. There are a wide variety of infectious and non-infectious disorders that may present with a pain in the right lower quadrant, mimicking appendicitis, ie, pseudoappendicitis. Influenza predisposes to some types of bacterial infection, eg, influenza pneumonia may be complicated by simultaneous Staphylococcus aureus community-acquired pneumonia or subsequent community-acquired pneumonia due to Haemophilus influenzae or Streptococcus pneumoniae. It remains unclear if there is direct involvement of the appendix, ie, pseudoappendicitis as occurs with measles or if influenza itself somehow predisposes to increased frequency/severity of bacterial appendicitis. German clinicians first noted an increased incidence of acute appendicitis in children/young adults with influenza. The American and British cases of influenza and acute appendicitis compared to age-matched controls with more severe and of delayed onset/complicated by appendicial perforation/abscess. These reports noted an increased incidence/severity of acute appendicitis during influenza.

Methods And Results: A 15-year-old girl presented to the hospital with an influenza-like illness and right lower quadrant abdominal pain. Acute appendicitis was diagnosed by a computed tomography scan and the patient underwent emergency appendectomy. Subsequently, it was noted that she did not have leukocytosis and, in fact, had borderline leukopenia. Her differential white blood cell count also revealed relative lymphopenia. Neither leukopenia nor relative lymphopenia are features of acute bacterial appendicitis. These two findings in the setting of an influenza-like illness indicate the underlying presence of influenza. Post-operatively, respiratory secretion samples were sent for swine influenza (H1N1) testing. Both her respiratory florescent antibody (FA viral panel) was positive for influenza A, as was her RT-PCR for swine influenza (H1N1). The authors believe that this is the first case of swine influenza (H1N1) and acute bacterial appendicitis. Direct involvement of the appendix by swine influenza (H1N1) virus could not be demonstrated.

Conclusions: The authors conclude that during the swine influenza (H1N1) pandemic clinicians should be alert to the possibility of an increased incidence/severity of acute bacterial appendicitis in patients with swine influenza (H1N1) infection.