Charles E. Stewart
EPIDEMIOLOGY
Appendicitis is common. Always consider appendicitis in the patient with abdominal pain who has not had an appendectomy. The lifetime incidence of appendicitis is about 7% to 9%, making appendicitis the most common abdominal surgical emergency. The lifetime risk for appendicitis is slightly higher for men than for women (8.6% and 6.7%, respectively).
Preoperative diagnosis of acute appendicitis has improved due to imaging techniques, but misdiagno-sis remains an important cause of successful malpractice claims against emergency physicians.
PATHOPHYSIOLOGY
Acute appendicitis develops from obstruction of the appendiceal lumen. Increased luminal pressure leads to vascular compromise, bacterial invasion, inflammatory response, and resultant tissue necrosis with possible perforation and peritoneal contamination.
Classically, appendicitis is associated with the migration of pain from the periumbilical area to the right lower quadrant (RLQ). However, there are many atypical presentations, often affected by variability of the anatomic location (eg, retrocecal, retroileal) of the appendix.
CLINICAL FEATURES
The most reliable symptom in acute appendicitis is abdominal pain.
RLQ pain is 81% sensitive and 53% specific for the diagnosis of acute appendicitis. Migration of periumbilical pain to the RLQ is 64% sensitive and 82% specific for the diagnosis of acute appendicitis.
After the onset of vague abdominal pain, the classic triad of symptoms in appendicitis includes anorexia, nausea, and vomiting. Sixty percent of patients with appendicitis will have some combination of these symptoms, but they are by themselves neither specific nor sensitive for appendicitis.
McBurney’s point tenderness, Rovsing’s sign, psoas sign, obturator sign, rectal examination tenderness, and rebound tenderness are all clinical examination findings that may be present. In children, the most reliable sign on physical examination is rebound tenderness.
Fever in appendicitis is a relatively late finding and rarely exceeds 39°C (102.2°F) unless rupture or other complications occur. As might be expected, fever is unreliable as an indicator for appendicitis. A temperature >99.0°F had a sensitivity of 47% (95% CI = 36%-57%) and a specificity of 64% (95% CI = 57%-71%).
DIAGNOSIS AND DIFFERENTIAL
The diagnosis of appendicitis is primarily clinical. Factors that increase the likelihood of appendicitis, listed in decreasing order of importance, are RLQ pain, rebound tenderness and/or rigidity, migration of pain to the RLQ, pain before vomiting, positive psoas sign, fever, and guarding. None of these factors are specific for appendicitis.
The differential diagnosis of appendicitis can include other RLQ GI complaints including volvulus, colitis, ileitis, bowel obstruction, diverticulitis, Crohn’s disease, intrabdominal abscess, intussusception, incarcerated hernias, gut malrotation, and mesenteric lymphadenitis. Genitourinary (GU) complaints that can mimic appendicitis include ovarian torsion, ectopic or hetertopic pregnancy, ovarian vein thrombosis and tubo-ovarian abscess or salpingitis in the female. In the male, testicular pain can be referred to the RLQ. Pyelonephritis or renal colic may cause RLQ pain in both women and men. Abdominal wall or rectus sheath hematomas and abscess within the psoas can also mimic appendicitis. Again, if the patient has right-sided abdominal pain, appendicitis should be considered unless a prior appendectomy has been done.
If the diagnosis is unclear, additional studies such as complete blood count, urinalysis, pregnancy test, and radiologic imaging should be considered.
Elevation of the white blood cell count is sensitive, but has a very low specificity for appendicitis.
Obtaining a urinalysis is important to rule out other diagnoses, such as urolithiasis or urinary tract infection; however, pyuria and hematuria can occur when an inflamed appendix overlies a ureter. Obtain a pregnancy test in every female of childbearing age who has a uterus.
Plain radiographs of the abdomen often have nonspecific abnormalities. Radiographic findings of possible acute appendicitis include appendiceal fecalith, appendiceal gas, localized paralytic ileus, blurred right psoas muscle, and free air.
Ultrasound is operator dependent and is significantly better in institutions where it is routinely used. Ultrasonography is limited in evaluating a ruptured appendix or an abnormally located (eg, retrocecal) appendix and in the obese patient. Ultrasound should be considered as an initial study for females and children as a means to limit radiation exposure (see Fig. 45-1).
Computed tomography (CT) is sensitive (98%) and quite specific (95%). Debate exists whether focused appendiceal CT or traditional nonfocused abdominal CT is the better choice and whether contrast need be used. CT findings suggesting acute appendicitis include pericecal inflammation, abscess, and peri-appendiceal phlegmon or fluid collections. Recent increases in use of CT scan have led to concerns about radiation risks to the patient (see Fig. 45-2).
Magnetic resonance imaging (MRI) may be useful for pregnant patients as there is no radiation involved in the diagnosis of appendicitis. Although MRI avoids any ionizing radiation and is deemed to be safe in pregnancy, it is more costly, time consuming, and of limited availability in most emergency departments. This significantly limits its usefulness in other patients.
In order to avoid premature surgical intervention or discharge of the patient with an uncertain diagnosis, patients with atypical presentations may be observed with serial abdominal examination.
The overall mortality rate for appendicitis is less than 1%, but it increases to 3% if the appendix is ruptured and approaches 15% in the elderly. The diagnosis of appendicitis is more difficult in the extremely young and the elderly, resulting in a higher incidence of delayed diagnosis and rupture with subsequent increases in mortality in these populations.
Appendicitis is the most common extrauterine surgical emergency in pregnancy, and occurs with an incidence equal to that of nonpregnant patients; if perforation and peritonitis occur, then fetal mortality rates are high.
FIG. 45-1. Ultrasonographic demonstration of acute appendicitis. A noncomprehensible inflamed appendix (red circles) is shown in a cross-sectional view (A; 7.5 MHz) and a longitudinal section (B; 7.5 MHz). Mural lamintion of the swollen appendix is maintained in the early stages of acute appendicitis. C. An appendicolith (arrow) with acoustic shadowing is demonstated (5 MHz). (Reprinted with permission from Ma OJ, Mateer JR, Blaivas M: Emergency Ultrasound, 2nd ed. Copyright © The McGraw-Hill Companies, 2008. All rights reserved. Chaper 9: General Surgery Applications, Figure 9–23, Parts A-C.)
FIG. 45-2. Acute appendicitis on contrast CT scan as evidenced by dilated and inflamed appendix (red circle).
EMERGENCY DEPARTMENT CARE AND DISPOSITION
In the United States, prompt surgical removal of the appendix is considered the most appropriate therapy.
Prior to surgery, patients should have nothing by mouth, and should have IV access, analgesia, and antibiotic therapy started.
Short-acting narcotic analgesics such as fentanyl (0.01–01.0 milligram/kg) are preferred, since they can be reversed by time or naloxone if necessary.
Antibiotics should cover anaerobes, enterococci, and gram-negative intestinal flora. Antibiotics given before surgery decrease the incidence of postoperative wound infection or, in cases of perforation, postoperative abscess formation. Several antibiotic regimens to cover anaerobes, enterococci, and gram-negative intestinal flora have been recommended, including piperacillin/tazobactam 3.375 grams IV or ampicillin/sulbactam 3 grams IV.
If no precise diagnosis is determined after evaluation and observation, the patient should be diagnosed as having nonspecific abdominal pain rather than be given a more specific diagnosis.
Patients who have no contraindication to discharge should be given specific instructions to obtain close follow-up with their primary care physician, and to return if their condition worsens or if they develop increased pain, fever, or nausea. The physician should ensure that a responsible party: parent or patient, understands that reevaluation can prevent serious complications and that diagnostic tests are not infallible.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 84, “Appendicitis,” by E. Paul DeKoning.