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More than 300,000 appendectomies for acute appendicitis are performed each year in the U.S.,1 with an additional 700,000 patients affected in the European community.2 Although some studies suggest that the incidence of acute uncomplicated appendicitis is falling in Western countries, the incidence of complicated appendicitis (e.g., perforation) may actually be increasing.3,4 It has been estimated that the lifetime risk of developing acute appendicitis in the U.S. is 12% for males and 25% for females.5 Appendicitis remains the most common etiology of atraumatic abdominal pain in children >1 year old6 and is the most common nonobstetric surgical emergency in pregnancy, complicating up to 1 in 1500 pregnancies.7,8 Despite technologic advances in lab testing and imaging, accurate diagnosis is a challenge. Both “missed appendicitis” and unnecessary surgery for a false diagnosis are not without consequence. Thus, consider appendicitis in any patient with acute atraumatic abdominal pain without a previous appendectomy.

Appendicitis is caused by luminal obstruction of the vermiform appendix, typically by a fecalith. Other less frequent causes include obstruction by lymphatic tissue, gallstone, tumor, or parasites. Continued secretion from the luminal mucosa results in increased intraluminal pressure and appendiceal vascular insufficiency, leading ultimately to bacterial proliferation and inflammation. If the process is left unchecked, perforation may occur.

Visceral innervation produces the vague, hard to localize periumbilical or central abdominal discomfort frequently observed early in the course of disease. Progressive local inflammation and subsequent irritation of the somatically innervated parietal peritoneum produces the classic migration of pain to the right lower quadrant, to the McBurney point, located one third of the distance on a line traced superomedially from the anterior superior iliac spine to the umbilicus. As many as one third of patients may have an atypical presentation of acute appendicitis.9 Anatomic variation is one cause of atypical presentations. For example, a retrocecal appendix can produce right flank or pelvic pain, whereas malrotation of the colon results in transposition of the appendix and, subsequently, pain to the left upper quadrant. Displacement of the abdominal organs from a gravid uterus may lead to right upper quadrant tenderness in pregnancy. However, a right lower quadrant location of pain remains the most common location of pain in pregnant women with appendicitis.8

The signs and symptoms of acute appendicitis lie along a spectrum that correlates with pathophysiology and varies depending on the location of the appendix. Early on, patients classically complain of nonspecific symptoms of general malaise, indigestion, or bowel irregularity. Anorexia is common but not universally present. Alterations in bowel function are variable and can include constipation, diarrhea, and even obstruction as a late complication.10 Periumbilical or central abdominal pain generally develops after nonspecific symptoms. Nausea, with or without emesis, if present, typically follows the onset of pain.11 Subjective or objective fever is a frequent but variable complaint. As the clinical course progresses, discomfort migrates to the right lower quadrant. Flank pain, ...

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