Appendicitis develops due to obstruction of the appendiceal orifice with secondary mucous accumulation, swelling, ischemia, necrosis, and perforation.

Obstruction of the appendix by one of a variety of causes

(e.g., lymphoid hyperplasia, fecaliths, infection such as parasites, tumor)

leads to an increase in luminal and intramural pressure.



Appendicitis is inflammation of the vestigial vermiform appendix.

Image not available.

Early acute appendicitis. Note the swelling of the appendix and the creamy yellow exudate on the surface (pus). Photograph by Dr. Gary Dale, Forensic Science Division, Montana State Department of Justice, Missoula, MT.



Bacterial overgrowth is accompanied by inflammation. If there is necrosis, perforation followed by diffuse peritonitis caused by bacteria of the normal colonic flora (e.g., E. coli and Bacteroides) may occur. Rupture of an inflamed appendix will lead to seeding of the peritoneal cavity with bacteria and a resultant peritonitis, which has a higher mortality rate.


Early in the course of the disease, the predominant organisms are anaerobic. In late disease, mixed organisms predominate. Escherichia coli, Peptostreptococcus, Bacteroides fragilis, and Pseudomonas are commonly isolated. 

Yersinia, Campylobacter, and Salmonella can cause an acute ileitis and mesenteric adenitis that can mimic appendicitis.

Complications include perforation and abscess formation.


Appendicitis is one of the most common surgical emergencies in contemporary medicine, with a yearly incidence rate of about 100 per 100,000 inhabitants.

The highest incidence is in the second decade of life.1

1. NPO

2. Intravenous fluids

3. Broad-spectrum intravenous antibiotics with gram-negative and anaerobic coverage to reduce the incidence of postoperative infections.

Intravenous regimens include

cefoxitin or cefotetan 1–2 g every 8 hours;

ampicillin-sulfabactam 3 g every 6 hours;

or ertapenem 1 g as a single dose.

4. Frequent clinical observation is critical in patients with an unclear diagnosis. One should start intravenous fluids and broad-spectrum antibiotics

5. Decision: Operative or nonoperative

[and obtain a STAT surgical consult as urgent appendectomy is the treatment of choice.]

Rupture of the appendix leads to peritonitis and possible death 

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Content 11


Which of the following tests has the highest sensitivity (i.e., misses the fewest) for appendicitis?

The correct answer is C.


Content 2

Content 3

A 32-year-old woman is evaluated in the emergency department for abdominal pain. She reports a vague loss of appetite for the past day and has had progressively severe abdominal pain, initially at her umbilicus, but now localized to her right lower quadrant. The pain is crampy. She has not moved her bowels or vomited. She reports that she is otherwise healthy and has had no sick contact. Exam is notable for a temperature of 100.7°F and heart rate of 105 bpm, but otherwise, vital signs are normal. Her abdomen is tender in the right lower quadrant, and pelvic examination is normal. Urine pregnancy test is negative. Which of the following imaging modalities is most likely to confirm her diagnosis?

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The correct answer is A. You answered A.

The answer is A.  The patient presents with typical findings for acute appendicitis with anorexia, progressing to vague periumbilical pain, followed by localization to the right lower quadrant. Low-grade fever and leukocytosis are frequently present. Although acute appendicitis is primarily a clinical diagnosis, imaging modalities are frequently employed because the symptoms are not always classic. Plain radiographs are rarely helpful except when an opaque fecalith is found in the right lower quadrant (<5% of cases). Ultrasound may demonstrate an enlarged appendix with a thick wall but is most useful to rule out ovarian pathology, tubo-ovarian abscess, or ectopic pregnancy. The effectiveness of ultrasonography as a tool to diagnose appendicitis is highly operator dependent. Even in very skilled hands, the appendix may not be visualized. Its overall sensitivity is 0.86, with a specificity of 0.81. Nonenhanced and contrast-enhanced CT are superior to ultrasound or plain radiograph in the diagnosis of acute appendicitis with sensitivity of 0.94 and specificity of 0.95. Findings often include a thickened appendix with periappendiceal stranding and often the presence of a fecalith. Free air is uncommon, even in the case of a perforated appendix. Nonvisualization of the appendix on CT is associated with surgical findings of a normal appendix 98% of the time. Colonoscopy has no role in the diagnosis of acute appendicitis.


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