Acute appendicitis is one of the most frequent surgical conditions seen by the general surgeon and is the most common indication for appendectomy. Appendicitis occurs when the lumen of the appendix becomes occluded—typically by a fecolith—leading to progressive distension of the distal portion of the organ (Fig. 15.1). Since the visceral peritoneum lacks the ability to accurately localize pain, this appendiceal distension first registers as a vague periumbilical pain. As the inflammation progresses, the parietal peritoneum overlying the appendix becomes irritated, which then localizes the process to an area in the right lower quadrant known as McBurney’s point. This migration of pain typically occurs over the first 24 h of illness, and therefore classic right lower quadrant pain may not yet be present in very early appendicitis.

While patients of any age can get appendicitis, it is far more common in children and young adults. It is important to keep in mind that patients at the extremes of age have the highest mortality from appendicitis, precisely because it is unsuspected in these age groups, and the very young and very old are often not able to describe their symptoms accurately, contributing to the delay in diagnosis. If treatment is delayed, perforation of the appendix can occur, leading to diffuse peritonitis and sepsis.

Typical physical exam findings associated with appendicitis are Rovsing’s sign, the obdurator sign, and the psoas sign. All three maneuvers elicit right lower quadrant abdominal pain by irritating the inflamed appendix, and their presence or absence can vary depending on the location of the appendix in relation to nearby structures (Fig. 15.2). It is important to note that several other processes can mimic appendicitis, particularly in female patients where pelvic inflammatory disease, tubo-ovarian abscess, ovarian torsion, and ectopic pregnancy must all be considered. Although in many cases appendicitis can reliably be diagnosed on the basis of a history and physical exam alone, CT imaging has now become a routine part of the work-up. On imaging, the appendix will appear distended, thick-walled, and will not fill with oral contrast; streaking in the periappendiceal fat indicates edema and inflammation (Fig. 15.3).

The treatment of appendicitis is almost always prompt appendectomy to remove the source of infection. However, in certain cases of perforated appendicitis, it is more prudent to avoid the operating room altogether. In the setting of intense inflammation, the surrounding intestines become edematous and friable, greatly increasing the potential morbidity from an appendiceal stump leak or inadvertent enterotomy. Therefore, it is occasionally appropriate to perform CT-guided percutaneous drainage of the intra-abdominal abscess and wait for the process to resolve while administering intravenous antibiotics.