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Studies examine use of computed tomography and risk of rupture in acute appendicitis

Computed tomography (CT) scans are being increasingly used to diagnose patients with suspected acute appendicitis. While use of CT scans does not harm patients with acute appendicitis, one study found that it does not translate to better overall outcomes and can delay surgery. A second study found that the risk of rupture in acute appendicitis, which can lead to serious infection or death, rises from 0 percent at 12 hours of untreated symptoms to 5 percent after 36 hours of untreated symptoms. Both studies were supported by the Agency for Healthcare Research and Quality (HS09698) and are summarized here.

Menes, T.S., Aufses, A., Rojas M., and Bickell, N.A. (2006, April). "Increased use of computed tomography does not harm patients with acute appendicitis." The American Surgeon 72, pp. 326-329.

These investigators examined the use of CT, delay in time to surgery as a result of CT use, and rupture rates in patients with appendicitis who underwent surgery in two periods: Phase 1, 1996 through 1998 (prior to common use of CT in these patients) and Phase 2, 2001 through 2002. CT was performed in 18 percent of the Phase 1 group compared with 62 percent in the Phase 2 group.

In the Phase 1 group, patients undergoing CT had a large delay to surgery compared with those without CT (18.6 hours vs. 7 hours). In the Phase 2 group, time to surgery was reduced to a median of 12 hours with CT, but still took twice as long (6 hours without CT). CT was also more accurate in the latter group with fewer false-negative and equivocal studies.

Overall, 35 percent of patients in Phase 1 who underwent a CT scan had a perforated appendix compared with 12 percent of non-CT patients. In Phase 2, 23 percent of patients who had CT scans had a ruptured appendix compared with 19 percent of non-CT patients. Over time with increased experience and efficiency, use of CT scans was not associated with increased time to surgery or higher rupture rates. Yet, the small percentage of patients with false-negative scans (that incorrectly showed no appendicitis) continued to experience longer time to surgery and higher rates of rupture. The researchers concluded that CT did not harm but did not translate to better overall outcomes for patients with acute appendicitis.

Bickell, N.A., Aufses Jr., A.H., Rojas, M., and Bodian, C. (2006, March). "Time and risk of rupture in appendicitis." Journal of the American College of Surgeons 202, pp. 401-406.

In 2000, 13 percent of patients hospitalized with acute appendicitis suffered a ruptured appendix. A ruptured appendix puts patients at risk for peritonitis (infection of the lining of the stomach and pelvis), sepsis (bloodstream infection), and death. Researchers conducted a retrospective chart review of 219 patients with appendicitis and found that rupture risk was 2 percent or less in patients with less than 36 hours of untreated symptoms prior to surgery. For patients with untreated symptoms beyond 36 hours, the risk of rupture rose to and remained steady at 5 percent for each ensuing 12-hour period. Risk of rupture was greater in patients with 36 hours or more of untreated symptoms, who were 65 years or older, who had a fever over 38.9 degrees C, or who had tachycardia (a heart rate of 100 beats or more per minute).

The time between first physician examination and treatment was shorter among patients who arrived at the emergency department compared with patients who first saw a physician outside the hospital (a median of 7.1 vs. 10.9 hours). Patients for whom a physician's leading diagnostic impression was appendicitis had shorter times to operation compared with patients with an uncertain diagnosis (6.3 vs. 11.3 hours). Patients sent for a CT scan waited longer for surgery compared with patients who did not receive a CT scan (18.6 vs. 7.1 hours). Over half of patients (57 percent) did not arrive at the hospital until they experienced symptoms for at least 24 hours, and 42 percent did not undergo an operation within the first 48 hours of their symptoms. The rupture rate was 16 percent, similar to other hospital-based reports. The researchers conclude that increasing time between symptom onset and treatment may boost a patient's risk of rupture and recommend that physicians be cautious about delaying surgery beyond 36 hours from symptom onset in patients with acute appendicitis.

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