Appendicitis is the commonest surgical emergency in children and its prompt identification is often challenging. Meticulous history and physical examination supported by the judicious use of diagnostic imaging are the mainstays of its diagnosis.

Lifetime appendicitis risk is approximately 8%, with males slightly higher than females. Under the age of 3 years, perforation rates are close to 100%, likely secondary to delays in presentation, and missed diagnosis secondary to overlap of symptoms with more common ailments such as gastroenteritis. In adolescence, perforation rates decrease to approximately 15%. Appendicitis is more common in the early summer when enteric infections are high as well.¹

The infant’s appendix is somewhat funnel-shaped and becomes tubular after the age of 2 years.¹ Appendicitis begins with luminal obstruction by an appendicolith, foreign body, parasite, or lymphoid follicle hyperplasia. This leads to continued inflammation, mucous production, and eventual perforation resulting in peritonitis or abscess formation. Perforation rates range between 25% and 40%.

Missed appendicitis is one of the most frequent reasons for litigation in pediatrics. Appendicitis is missed upon first presentation up to 28% of the time. Gastroenteritis, constipation, and urinary tract infections are common diagnoses in those patients with a misdiagnosis.¹

The history is a crucial part of the evaluation of acute appendicitis, and particular features of the history will vary with age. The diagnosis is particularly challenging in children less than 3 years old because preverbal children cannot provide history, and the clinical course is often more rapid and frequently atypical compared with older children. Young children will more often have vomiting and irritability as their primary presentation, which has significant overlap with other diagnoses. Abdominal pain is not easy to elicit from a history, and if so, the patients are less likely to have focal right lower quadrant pain than older children. Because they frequently have perforated appendicitis at diagnosis, they have higher temperatures and higher rates of bilious emesis and bowel obstruction.

As children become more verbal, and the anatomy of the appendix changes, the historical features tend to become more reliable. The classic presentation of periumbilical pain, nausea, and migration of pain to the right lower quadrant is less frequent in children and is only reported in about one-third of patients. As opposed to adults, children are more likely to present with vomiting first, then followed by abdominal pain. Diarrhea is a frequent complaint and should not be assumed to indicate gastroenteritis. Older children often report anorexia, and pain with walking, coughing, or jumping.

Referred pain to the abdomen mimicking appendicitis is also common, and asking about respiratory and genitourinary symptoms is important. A classic example is a right lower lobe pneumonia that refers pain to the abdomen mimicking appendicitis.¹

Low-grade fever is often present early in the course of appendicitis but its absence does not rule it out. Tachycardia is a nonspecific finding noted in most children presenting with pain or fever. It is important to evaluate the child’s perfusion and respiratory status, assessing for evidence of compensated or decompensated shock. The classic findings of right lower quadrant tenderness, vomiting, and fever are less frequent in children than adults, especially in younger children. Evaluation of gait is a nonthreatening way to assess for peritoneal irritation. If they are in pain, they may walk hunched over or may be unable to walk at all. Younger children with significant stranger anxiety can be very difficult to examine. It is best, if possible, to examine these children in the arms of the caregiver, and one should pay special attention at this age to abdominal findings such as irritability with palpation, firmness, or distension. As children grow older and become verbal, the utility of bedside tests of peritoneal irritation (Table 51-1) becomes more useful. Pain with coughing, jumping, or walking can be elicited during the course of examination, and its presence increases the likelihood of appendicitis.

Chest and pulmonary examination may reveal lower-lobe crackles suggesting pneumonia. The genitalia should be examined. Testicular torsion and hernias can present with referred pain to the abdomen mimicking appendicitis. The rectal examination is of low utility and is best avoided.¹

A suggestive history and consistent physical examination is often enough evidence to proceed directly to surgery without further testing. This decision is surgeon- and institution-dependent. A multidisciplinary care guideline can often minimize variation, and recent evidence shows decrease in ancillary testing in settings where these guidelines exist.²