Appendicitis is a common cause of abdominal pain, occurring in children of all ages. Appendicitis is typically caused by obstruction of the appendiceal lumen, resulting in appendiceal distention, inhibition of lymphatic and vascular drainage, edema, and perforation.

The classic symptoms of appendicitis are periumbilical abdominal pain, followed by fever, anorexia, and vomiting. As the disease progresses, pain localizes to the right lower quadrant (i.e., McBurney’s point). However, patients with appendicitis
often present atypically and with nonspecific symptoms. An appendix situated in the lateral colonic gutter may cause flank pain, while an appendix positioned more medially may irritate the bladder and cause dysuria and suprapubic pain. Alternatively, an appendix positioned in the pelvis may cause diarrhea if the inflamed appendix irritates the sigmoid colon. Patients may prefer to lie still because of the peritoneal irritation caused by an inflamed appendix, and children may report increasing pain with coughing or jumping.

Unfortunately, making the diagnosis of appendicitis can be challenging, especially in preverbal children in the early stages of the disease process. As a result, young patients frequently present after the appendix has perforated. These patients may report transient improvement of their pain immediately after perforation but soon complain of diffuse abdominal pain from peritonitis. Patients with appendiceal perforation may go on to develop intra-abdominal abscesses (see Chapter 8, “Abdominal Mass”).

The physical examination frequently reveals a fever and tenderness in the right lower quadrant, although fever may be absent and tenderness may be found in the flank or elsewhere in the abdomen, depending on the location of the appendix. The Rovsing sign (pain in the right lower quadrant with palpation of the left lower quadrant), the psoas sign (pain in the right lower quadrant with extension of the right thigh while the patient is lying on his or her left side), and the obturator sign (pain in the right lower quadrant when the flexed thigh and knee are held and the hip is rotated internally) are all signs that may be seen with appendicitis. A rectal examination may reveal irritation of the rectal wall by an inflamed appendix. If the appendix has perforated and the child has developed peritonitis, he or she may have diffuse abdominal tenderness, rebound tenderness, and abdominal wall rigidity. These children frequently also have signs of systemic toxicity, such as a high fever, tachycardia, and tachypnea.

Laboratory studies can be helpful in cases where the history and physical examination are equivocal. A peripheral white blood count often reveals a mild leukocytosis with an increasing left shift as the appendix becomes more gangrenous or ruptures; however, a normal white blood cell count does not rule out appendicitis. Electrolytes are usually not abnormal unless significant dehydration exists. A few white blood cells in the urine may be found if the appendix lies near the bladder or the ureter. Plain radiographs of the abdomen may occasionally reveal an appendicolith. More commonly, however, the x-ray findings are nonspecific. Diagnostic accuracy is enhanced in patients with equivocal presentations for appendicitis by
the use of either abdominal ultrasound and/or abdominal computed tomography (CT) scan. Ultrasound spares the child from ionizing radiation but more frequently results in indeterminate results than CT. CT scans are better at identifying other diagnoses that might cause abdominal pain and are generally more easily obtainable than ultrasound studies, but young patients frequently require sedation.