How time affects the risk of rupture in appendicitis

Increasing time between symptom onset and treatment may be a risk factor for a ruptured appendix, but little is known about how the risk changes with passing time. This study aimed to determine the changes in risk of rupture in patients with appendicitis with increasing time from symptom onset to treatment to help guide the swiftness of surgical intervention.

We conducted a retrospective chart review of physician office, clinic, emergency room, and inpatient records of a random sample of 219 of 731 appendicitis patients operated on between 1996 and 1998 at 2 inner-city tertiary referral and municipal hospitals. Conditional risks of rupture were calculated using life table methods. Logistic regression was used to assess factors associated with rupture, and linear regression was used to assess factors affecting time from first examination to treatment.

Rupture risk was < or = 2% in patients with less than 36 hours of untreated symptoms. For patients with untreated symptoms beyond 36 hours, the risk of rupture rose to and remained steady at 5% for each ensuing 12-hour period. Rupture was greater in patients with 36 hours or more of untreated symptoms (estimated relative risk [RR]=6.6; 95% CI: 1.9 to 8.3), age 65 years and older (RR=4.2; 95% CI: 1.9 to 6.1), fever > 38.9 degrees C (RR=3.6; 95% CI: 1.2 to 5.7), and tachycardia (heart rate > or = 100 beats/minute; RR=3.4; 95% CI: 1.8 to 5.4). Time between first physician examination and treatment was shorter among patients presenting to the emergency department (median, 7.1 hours versus 10.9 hours; p<0.0001), and those for whom a physician's leading diagnostic impression was appendicitis (6.3 hours versus 11.3 hours; p<0.0001). Patients sent for CT scan experienced longer times to operation (18.6 hours versus 7.1 hours; p<0.0001).

Risk of rupture in ensuing 12-hour periods rises to 5% after 36 hours of untreated symptoms. Physicians should be cautious about delaying surgery beyond 36 hours from symptom onset in patients with appendicitis.