What is the best course of action for a patient with suspected appendicitis, presenting with mild right lower quadrant pain and a normal white blood cell (WBC) count, to avoid missing the diagnosis?

Admit for Serial Abdominal Examination and Repeat Laboratory Testing

In a patient with suspected appendicitis presenting with mild right lower quadrant pain and normal WBC count (9,000), you should admit for serial abdominal examinations and repeat laboratory testing in 6-12 hours to avoid missing the diagnosis. 1

Rationale for Admission and Observation

The clinical presentation described represents an atypical or early presentation of appendicitis where laboratory values may not yet reflect the underlying pathology. 1

Why Normal WBC Does Not Rule Out Appendicitis

• An elevated WBC count (>10,000/mm³) has poor sensitivity of only 76% and specificity of 52% for appendicitis, meaning nearly one-quarter of patients with confirmed appendicitis will have a normal WBC count. 2
• The negative predictive value of a normal WBC count is only 82%, which is insufficient to safely exclude appendicitis in a patient with clinical suspicion. 2
• The classic presentation of appendicitis (including fever and leukocytosis) is present in only approximately 50% of patients, making atypical presentations common. 1
• Normal laboratory values, including WBC, are frequently seen in patients with appendicitis, particularly in early disease. 1

The Value of Serial Examination

• Serial abdominal examinations over 6-12 hours allow for detection of evolving peritoneal signs that may not be present at initial presentation. 1
• Clinical findings should be used to risk-stratify patients with suspected appendicitis and guide management decisions, with observation being appropriate for equivocal presentations. 1
• Repeat laboratory testing in 6-12 hours may reveal rising WBC counts or development of left shift, which significantly increases diagnostic accuracy when combined with clinical progression. 3

Why Discharge Is Inappropriate

Discharging this patient risks missing appendicitis during its early phase, potentially leading to progression to perforation with associated increased morbidity and mortality. 1

Consequences of Missed Diagnosis

• Historical perforation rates are approximately 19% in males and 18% in females, with perforation associated with significantly increased morbidity, mortality, and length of stay. 1
• The negative appendectomy rate based on clinical determination alone without imaging reaches 25%, but this statistic reflects the difficulty of diagnosis, not a reason to discharge uncertain cases. 1
• Delays in diagnosis increase the risk of perforation, which carries substantially worse outcomes than observation of a patient who ultimately does not have appendicitis. 1

Imaging Considerations During Observation

If the patient's clinical picture remains equivocal after initial observation, CT abdomen and pelvis with contrast is the most appropriate imaging modality, with sensitivities ranging from 85.7% to 100% and specificities from 94.8% to 100%. 1

When to Image

• Imaging should be considered if clinical findings remain equivocal after serial examination or if the patient's condition worsens during observation. 1
• CT without enteral contrast is acceptable and avoids delays associated with oral contrast administration, with sensitivity of 90-100% and specificity of 94.8-100%. 1
• Ultrasound has highly variable performance with sensitivities ranging from 21% to 95.7% and is less reliable than CT, particularly in patients with elevated body mass index. 1

Common Pitfalls to Avoid

• Do not rely on normal WBC count alone to exclude appendicitis, as this has insufficient negative predictive value and poor sensitivity. 2
• Do not discharge patients with clinical suspicion of appendicitis based solely on absence of fever and normal laboratory values, as the classic triad is present in only half of cases. 1
• Do not delay observation waiting for laboratory abnormalities to develop before admitting the patient, as early admission allows for timely detection of clinical progression. 1
• Avoid using temperature elevation as a discriminating factor, as a temperature >99°F has only 47% sensitivity and 64% specificity for appendicitis. 2