Appendicitis Review

Appendicitis is a transmural inflammatory process and a common cause of an acute abdomen. Inflammation that leads to perforation of the appendix, which is associated with increased morbidity and mortality, warrants prompt diagnosis. Etiology, clinical presentation, diagnostic studies, and the management of confirmed appendicitis will be addressed here.

Frequently, the etiology of appendicitis is luminal obstruction by a fecalith (the result of inspissated fecal material and inorganic salts¹), but the condition may also result from parasites, a malignancy, a foreign body, or fibrosis.^1-3 In some instances, lymphoid hyperplasia, resulting from a viral or bacterial infection, has been targeted as the cause of luminal obstruction.^1,4 Nevertheless, in one-third to one-half of patients, obstruction is not evident as a precipitating factor in the development of appendicitis. In such cases, the basis for the inflammation is unknown.⁵

As the obstructed appendix becomes congested, the intraluminal pressure and venous pressure increase, leading to stasis and ischemia.^1,5-8 The appendix becomes engorged with secretions. At this stage, the condition is considered uncomplicated, but if an inflamed appendix becomes gangrenous or perforates, the condition is then referred to as complicated appendicitis. Complicated appendicitis allows for invasion by intestinal bacteria of the abdominal cavity, potentially leading to peritonitis, septicemia, abscess, or fistula formation.^5,9

Conventional teaching supports the concept that uncomplicated appendicitis, unless treated surgically, eventually evolves into complicated appendicitis.¹⁰ Recent research refutes this assumption, however, as different etiologies may be associated with differences in progression^10-12; whether uncomplicated and complicated appendicitis are attributable to different etiologies is a question requiring further research. Irrespective of the natural progression of the disease, the current standard of care for appendicitis is still an appendectomy.¹³ In US hospitals in 2007 (the most recent year for which data are available), appendectomy was performed on 326,000 patients, or 10.9 patients per 10,000 population.¹⁴

EPIDEMIOLOGY

Appendicitis is most frequently seen in the second decade of life and occurs slightly more often in males than in females.^2,15 Furthermore, according to data reported to the National Hospital Discharge Survey (1970 to 2004), the rate of nonperforated appendicitis is much higher in men than in women.¹² In appendicitis, the risk for rupture is small within the first 36 hours of symptom onset. Beyond that point, there is a 5% increased risk for rupture with each ensuing 12-hour period.¹⁶

In neonates and infants, appendicitis is rare.³ In children younger than 3 years, however, the rate of perforation is 80% to 100%.^3,17,18 This high rate may be explained by the very young child’s limited ability to articulate his or her symptoms, or by caregiver reports that are typically limited to irritability or change in diet.^3,17,19 According to Marudanayagam et al,² who performed a retrospective study of 2,660 appendectomies during a six-year period, the perforation rate declined from 23.4% in patients age 10 or younger to 6.9% in those in their 20s, then rose steadily to more than 50% in patients 70 or older.

PATIENT EVALUATION

In most cases, a diagnosis of appendicitis can be made with a careful history, systematic physical exam, and a limited number of laboratory tests without special diagnostic modalities.¹³ The presence of symptoms and signs may help to rule in a diagnosis of appendicitis, but the absence of clinical findings often does not exclude its possibility.¹⁶ While adult and pediatric patients with appendicitis share many clinical findings (see Table 1^3,8,13,18), the occurrence rate of the various findings may differ among patient populations.^3,15

The median time from onset of symptoms until the patient presents for a medical evaluation averages 24 hours or less.¹⁶ Diagnosis in patients at extremes of age often proves more difficult than in other patients.²⁰ Thus, a high level of suspicion must be maintained in these patient populations.

The Symptom History

The appendix is located in the posteromedial wall of the cecum, approximately 3 cm below the ileocecal valve.¹ Initial pain perceived around the umbilicus represents a referred pain resulting from the visceral innervation of the midgut.²⁰ As the inflammatory process within the appendix advances, the pain localizes to the anatomical position of the right lower quadrant (RLQ), with involvement of the surrounding parietal peritoneum.²⁰(McBurney’s point, at the junction of the lateral and middle thirds of a line extending from the anterior superior iliac spine to the umbilicus, was noted as the point of maximal tenderness to palpation in acute appendicitis by Charles McBurney in the late 1800s.²¹)

This progression of symptoms, first recognized by John Benjamin Murphy in 1904, is considered a more reliable indicator of appendicitis than RLQ pain alone^3,22; in one large retrospective study, this migratory pain had the highest positive predictive value for pediatric and adult patients (94.2% and 89.6%, respectively).¹⁵ However, migration of pain occurs in only 50% to 60% of patients, and therefore may not be helpful.^1,23