 Introduction/Background Right lower quadrant (RLQ) abdominal pain accounts for nearly 50% of patients presenting to the emergency department with abdominal pain [1]. Appendicitis is the most common surgical pathology responsible for RLQ abdominal pain in the United States [1,2]. Other less frequent causes of RLQ pain include right colonic diverticulitis, ureteral stone, colitis, and intestinal obstruction [1,3,4]. Imaging remains the diagnostic mainstay in the workup of patients presenting with RLQ abdominal pain for evaluation of suspected appendicitis and diagnosis of other conditions. Buckius et al [2] reported an annual increase in the rate of acute appendicitis in the United States; however, Ferris et al [5], in a recent systematic review of population-based studies, showed that although the incidence of both perforated and nonperforated appendicitis is stable in North America, the incidence is rising in newly industrialized countries. Historically, the clinical determination of appendicitis has been poor, particularly in special patient populations, such as those at the extremes of age and pregnant women. The negative appendectomy rate (NAR) based on clinical determination alone without imaging is unacceptably high, as high as 25% [6]. Clinical decisions tools, such as the Alvarado score (AS), have not improved the outright diagnostic accuracy of the clinical examination [7] and demonstrate mixed results as an adjunct to help guide CT use [8,9]. The decrease in NAR with increased imaging utilization is not accompanied by an increase in perforations from any introduced delays [10,11]. The choice of imaging modality should be tailored for diagnosis of acute appendicitis in patients with a high degree of suspicion but should also allow diagnosis of other causes of RLQ pain to triage appropriate patient management.
Right Lower Quadrant Pain.  Introduction/Background Right lower quadrant (RLQ) abdominal pain accounts for nearly 50% of patients presenting to the emergency department with abdominal pain [1]. Appendicitis is the most common surgical pathology responsible for RLQ abdominal pain in the United States [1,2]. Other less frequent causes of RLQ pain include right colonic diverticulitis, ureteral stone, colitis, and intestinal obstruction [1,3,4]. Imaging remains the diagnostic mainstay in the workup of patients presenting with RLQ abdominal pain for evaluation of suspected appendicitis and diagnosis of other conditions. Buckius et al [2] reported an annual increase in the rate of acute appendicitis in the United States; however, Ferris et al [5], in a recent systematic review of population-based studies, showed that although the incidence of both perforated and nonperforated appendicitis is stable in North America, the incidence is rising in newly industrialized countries. Historically, the clinical determination of appendicitis has been poor, particularly in special patient populations, such as those at the extremes of age and pregnant women. The negative appendectomy rate (NAR) based on clinical determination alone without imaging is unacceptably high, as high as 25% [6]. Clinical decisions tools, such as the Alvarado score (AS), have not improved the outright diagnostic accuracy of the clinical examination [7] and demonstrate mixed results as an adjunct to help guide CT use [8,9]. The decrease in NAR with increased imaging utilization is not accompanied by an increase in perforations from any introduced delays [10,11]. The choice of imaging modality should be tailored for diagnosis of acute appendicitis in patients with a high degree of suspicion but should also allow diagnosis of other causes of RLQ pain to triage appropriate patient management.