Is the incidence of appendicitis reduced in patients with sickle cell disease?

BACKGROUND Patients with sickle cell disease (SCD) often present with abdominal pain, usually attributable to vasoocclusion. Experience at a single institution suggested that appendicitis was a rare cause of abdominal symptoms in this population. OBJECTIVE We sought to determine whether the incidence of appendicitis was significantly lower in patients with SCD than in the population at large. METHODS A 17-year retrospective chart review was performed at Rainbow Babies and Children's Hospital, Cleveland, OH, to determine the approximate incidence of acute appendicitis (AA) in patients with SCD. In addition, we performed a statistical analysis comparing the incidence of AA among SCD patients enrolled in the Cooperative Study of Sickle Cell Disease with that in the general population. RESULTS Only two patients with SCD with pathologically confirmed AA were identified among approximately 200 patients followed at our institution during a 17-year period ( approximately 3500 patient-years), yielding an incidence rate of 5.7 cases per 10 000 patient-years. Among 3765 patients with SCD enrolled in the Cooperative Study of Sickle Cell Disease followed for a mean of 5.3 years (19 886 patient-years), a maximum of 9 cases of AA were identified, yielding an incidence rate of 4.5 cases per 10 000 patient-years. Based on data from the National Hospital Discharge Survey of 1978 to 1981, the incidence rate of AA in the general population (0 to 44 years of age) is approximately 16 per 10 000 patient-years. Paired t test analysis demonstrated a highly significant difference (P < .001) when comparing the incidence of AA among patients enrolled in the Cooperative Study of Sickle Cell Disease and the population at large. CONCLUSION AA is an unusual event in patients with SCD. The likelihood of developing appendicitis in SCD patients is less than one third of that for the population at large. Conservative therapy is warranted in the large majority of patients with SCD who present with acute abdominal pain. Surgical exploration is best limited to patients with clear evidence of potential surgical pathology or progressive findings during a period of observation. The biologic basis of our findings remains unknown.