Obtain CT Abdomen and Pelvis with IV Contrast Immediately
The most appropriate step is to obtain CT abdomen and pelvis with IV contrast as the initial imaging study, not to discharge home or admit for serial observation alone. 1
Why Imaging is Mandatory Despite Normal Laboratory Values
Normal WBC count does not exclude appendicitis or other surgical pathology. The "classic" presentation of appendicitis (including fever and leukocytosis) occurs in only approximately 50% of patients, making clinical assessment and laboratory values unreliable for excluding serious pathology. 2, 1
Both WBC and CRP are insufficient as triage tests. Even when combined, normal WBC count and CRP cannot reliably distinguish between patients with and without appendicitis, though their combined absence makes appendicitis "very unlikely" but not impossible. 3, 4
CT imaging changes management in 43% of patients initially suspected to have appendicitis based on clinical presentation alone, demonstrating the inadequacy of clinical judgment without imaging. 1
CT as First-Line Imaging
The American College of Radiology recommends CT abdomen and pelvis with IV contrast as the imaging modality of choice for evaluating RLQ pain without leukocytosis, providing superior diagnostic accuracy (95% sensitivity, 94% specificity) for appendicitis. 1
CT identifies the cause of RLQ pain in the majority of cases, with 41% of patients with non-appendiceal diagnoses requiring hospitalization and 22% requiring surgical or image-guided intervention. 1
When CT excludes appendicitis in patients with RLQ pain and normal WBC, the most frequent alternative diagnoses include gynecologic conditions, gastrointestinal etiologies, genitourinary causes, vascular, and musculoskeletal causes. 1
Why Serial Observation Alone is Inadequate
Clinical determination of appendicitis is notoriously poor, with negative appendectomy rates as high as 25% when relying on clinical assessment alone, even with serial examinations. 5
Admitting for serial abdominal exams and repeat laboratory tests delays definitive diagnosis and risks missing early appendicitis or other time-sensitive pathology that requires intervention. 1, 5
The absence of fever and normal WBC count are common in early appendicitis and do not rule out the diagnosis. 5
Why Not Ultrasound First
Ultrasound has significantly lower sensitivity (51.8%) and specificity (81.4%) compared to CT in the general population with RLQ pain. 1
The appendix is not visualized in 27-45% of ultrasound examinations, leaving diagnostic uncertainty. 2
The American College of Radiology suggests considering ultrasound as the initial modality only in reproductive-age females where gynecologic pathology is the primary concern, not as a general first-line test for RLQ pain. 1
Critical Pitfall to Avoid
Never rely on normal WBC alone to exclude appendicitis or other surgical pathology—imaging is mandatory. 1 Discharging a patient home based solely on absence of fever and normal WBC would risk missing early appendicitis or other serious pathology requiring urgent intervention. 5