Disconnect between incidence of nonperforated and perforated appendicitis: implications for pathophysiology and management

Abstract

Objective: Appendicitis has been declining in frequency for several decades. During the past 10 years, its preoperative diagnosis has been made more reliable by improved computed tomography (CT) imaging. Thresholds for surgical exploration have been lowered by the increased availability of laparoscopic exploration. These innovations should influence the number of appendectomies performed in the United States. We analyzed nationwide hospital discharge data to study the secular trends in appendicitis and appendectomy rates.

Methods: All appendicitis and appendiceal operations reported to the National Hospital Discharge Survey (NHDS) 1970-2004 were classified as perforated, nonperforated, negative, and incidental appendectomies and analyzed over time and by various demographic measures. Secular trends in the population-based incidence rates of nonperforated and perforated appendicitis and negative and incidental appendectomy were examined.

Results: Nonperforated appendicitis rates decreased between 1970 and 1995 but increased thereafter. The 25-year decreasing trend was accounted for almost entirely by a decreasing incidence in the 10-19 year age group. The rise after 1995 occurred in all age groups above 5 years and paralleled increasing rates of CT imaging and laparoscopic surgery on the appendix. Since 1995 the negative appendectomy rate has been falling, especially in women, and incidental appendectomies, frequent in prior decades, have been rarely performed. Despite these large changes, the rate of perforated appendicitis has increased steadily over the same period. Although perforated and nonperforated appendicitis rates were correlated in men, they were not significantly correlated in women nor were there significant negative correlations between perforated and negative appendectomy rates.

Conclusion: The 25-year decline in nonperforated appendicitis and the recent increase in appendectomies coincident with more frequent use of CT imaging and laparoscopic appendectomies did not result in expected decreases in perforation rates. Similarly, time series analysis did not find a significant negative relationship between negative appendectomy and perforation rates. This disconnection of trends suggests that perforated and nonperforated appendicitis may have different pathophysiologies and that nonoperative management with antibiotic therapy may be appropriate for some initially nonperforated cases. Further efforts should be directed at identifying preoperative characteristics associated with nonperforating appendicitis that may eventually allow surgeons to defer operation for those cases of nonperforating appendicitis that have a low perforation risk.

FIGURE 1. Population adjusted secular trends for perforated and nonperforated appendicitis and negative appendectomy rates in males (A) and females (B). Nonperforated appendicitis was determined from diagnostic codes for the disease entity appendicitis. Time series analysis found a significant year-to-year correlation between residuals of nonperforated and perforated appendicitis rates in males (r = 0.55, P = 0.001) (C) but not in females (r = 0.21, P = 0.25) (D). The year-to-year changes in the residuals of the nonperforated appendicitis rates of males and females were correlated (r = 0.49, P = 0.004), as were those of negative appendectomy rates in males and females (r = 0.45, P = 0.009; data not shown).

FIGURE 2. Surgical trends for appendicitis 1979–2003. ICD-9-CM coding for laparoscopic appendectomy began in 1997. Before 1997 the total appendectomy rate was also the same as the open rate.

FIGURE 3. Rates of nonperforated appendicitis stratified by age (A) for 1970–2004 and detailed view (B) of 1995–2004.

FIGURE 4. Rate of computed tomography (CT) utilization for hospitalized patients with appendicitis (number of CT scans per 10,000 population).