Computer Tomography in Appendicitis: Errors
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Computer Tomography in Appendicitis: Errors

Computer tomography (CT) has had an important effect on the management of patients suspected of having appendicitis. Perceptive and interpretive errors may result from secondary involvement of small bowel by perforative appendicitis. Such secondary involvement mimics primary small-bowel disorders because of peritoneal dynamics and anatomic interrelationships.

Computer tomography (CT) has had an important effect on the management of patients suspected of having appendicitis. Perceptive and interpretive errors may result from secondary involvement of small bowel by perforative appendicitis. Such secondary involvement mimics primary small-bowel disorders because of peritoneal dynamics and anatomic interrelationships.

Among the specific problems encountered in the diagnosis of appendicitis is a failure to opacify the cecum and appendix. These common technical pitfalls and limitations result in no depiction of the normal appendix, which increases false-negative or false-positive diagnoses and lowers the diagnostic certainty of a normal examination. Such failure also results in the inability to depict the findings that are 100% specific for appendicitis: focal cecal apical thickening, the “arrowhead” sign, and the cecal bar adjacent to an appendicolith. Inadequate familiarity with the findings of appendicitis results in perceptive error.

Nonspecific features may be considered conclusive and specific findings and can be misapplied if the cecal apex is not identified. A learning curve exists in recognizing either the abnormal or the normal appendix . Lack of intraabdominal fat, especially in children, the elderly, and cachectic patients, increases the difficulty of finding the normal or abnormal appendix. Sonography, when expertise is available, is an important examination in this subset of patients, particularly in children. The CT technique should always include the intravenous administration of contrast material in these patients because of the resulting enhancement of the abnormal appendiceal wall and the demonstration of skip areas in the enhancement when the appendix is focally necrotic. A failure to monitor the examination and administer additional contrast material or to obtain different projections if needed to help clarify initially indeterminate findings is a pitfall that can be avoided. Volume averaging associated with CT section thickness greater than 5 mm can limit the ability to distinguish the appendix from adjacent structures.

Failure to use appropriate CT window settings, especially if free fluid is present, may obscure the appendix

and result in interpretive errors. Interpretive errors also result when the diagnostic threshold is too low for the CT diagnosis of acute appendicitis. Variation in the position of the cecum or appendix may cause difficulty in interpretation . The transverse cecum, cecal bascule, or malposition of the colon makes it imperative to identify the position of the cecum and terminal ileum before attempting to identify the appendix. Other interpretive problems include misidentification of an opacified vessel for the normal appendix or misidentification of a loop of unopacified small bowel for the abnormal appendix. Tip appendicitis, stump appendicitis, and secondary appendicitis may all present interpretive problems. As discussed in the section on the small bowel, findings secondary to appendicitis are often attributed to primary small-bowel diseases.

There are a variety of alternative diagnoses (or mimics), which should be sought because of the nonspecific clinical findings in appendicitis. Indeterminate CT examinations should be resolved by opacification of the cecum and appendix in the emergency department. A misleading clinical history also results in an interpretive pitfall.

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Comments (4)

Interesting and scary article! Voted up.

You have certainly explained these errors well.

Nice informative article. Well done. Voted up.

Outstanding piece of work.

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