The immunocompromised state alters the normal response to acute infection and wound healing. Appendicitis affects all types of patients and must be considered in those who have undergone organ transplantation, are receiving chemotherapy, have hematological malignancy, or are infected with the human immunodeficiency virus. The differential diagnosis of abdominal pain in this population is broad and includes hepatitis, pancreatitis (from medications or cytomegalovirus infection), acalculous cholecystitis, intra-abdominal opportunistic infections (cytomegalovirus colitis or mycobacterial ileitis), secondary malignancies (lymphoma or Kaposi’s sarcoma), graft-versus-host disease, and typhlitis. This broad differential diagnosis often results in delay in diagnosis and late presentation to surgical evaluation, at which time perforation may be more likely.
Appendicitis most commonly affects children age 10–19, with an overall incidence of approximately 20 cases per 10,000 population annually.Among those under age 20, infants age 0–4 have the lowest incidence of appendicitis (2 cases per 10,000 annually), but up to two-thirds will present with perforation. Perforation is common because infants often present later in their disease course and because of the difficulty in obtaining an accurate history. The diagnosis is further complicated by diseases of childhood that can mimic appendicitis. For instance, mesenteric adenitis, an inflammation of the mesenteric lymph nodes secondary to upper respiratory tract infection, can present with fever and right lower quadrant pain. Streptococcal pharyngitis and bacterial meningitis can also present with fever, nausea, and abdominal pain. These diagnoses should be considered when evaluating children for suspected appendicitis.
The diagnosis of acute appendicitis in the pregnant patient can be particularly challenging, as nausea, anorexia, and abdominal pain may be symptoms of both appendicitis and normal pregnancy. In addition, the gravid uterus can displace the abdominal viscera, shifting the location of the appendix from the right lower quadrant. Appendicitis affects 1 in every 1,400 pregnancies, an incidence similar to that of the nonpregnant female population.It can occur in any trimester, with perhaps a slight increase in frequency during the second trimester. Perforation is more common in the third trimester, however, and results from a longer duration from the onset of symptoms to operation. The differential diagnosis of appendicitis includes not only the conditions possible in nonpregnant women, but also certain conditions specific to pregnancy: ectopic pregnancy, chorioamnionitis, preterm labor, placental abruption, and round ligament pain.