How to manage a patient with suspected appendicitis without leukocytosis, particularly in older adults or immunocompromised individuals?

Management of Suspected Appendicitis Without Leukocytosis

Do not exclude appendicitis based on the absence of leukocytosis—proceed directly to CT imaging with IV contrast in adults, as approximately 15-16% of confirmed appendicitis cases present without elevated white blood cell counts or other inflammatory markers. 1

Critical Diagnostic Principle

Never rely on laboratory values alone to diagnose or exclude appendicitis. The World Journal of Emergency Surgery strongly recommends against basing the diagnosis of acute appendicitis only on elevated leukocyte count and CRP values, particularly in elderly patients. 2 Normal inflammatory markers do not reliably exclude appendicitis, with a negative likelihood ratio of only 0.25 for a normal WBC count. 3

• Appendicitis can occur with completely normal laboratory values, including normal WBC, CRP, and absence of fever. 3, 1
• In one series, 15.6% of patients with confirmed acute appendicitis presented with isolated right lower quadrant pain without fever, leukocytosis, or elevated CRP. 1
• Early appendicitis may not yet demonstrate laboratory abnormalities. 4

Imaging Strategy: The Definitive Approach

For Adults Under 60 Years

Order CT abdomen/pelvis with IV contrast immediately when clinical suspicion exists, regardless of laboratory values. 2

• CT has 100% sensitivity and 99.1% specificity in diagnosing appendicitis, with 95.7% positive predictive value and 100% negative predictive value. 2
• The American College of Radiology rates CT with contrast as "usually appropriate" (rating 8/9) for suspected appendicitis. 2
• CT correctly identified appendicitis in 96.1% of cases presenting without inflammatory markers. 1

For Elderly Patients (≥60 Years) and Immunocompromised

Use a conditional CT strategy after initial ultrasound to balance diagnostic accuracy with radiation exposure. 2

• Start with ultrasound with graded compression. 2
• If ultrasound is negative or equivocal AND clinical suspicion remains (Alvarado score ≥5), proceed immediately to CT with IV contrast. 2
• This approach reduces CT use by 50% while maintaining diagnostic accuracy. 2

Critical rationale for elderly patients: The typical triad of migrating right lower quadrant pain, fever, and leukocytosis is infrequently observed in elderly patients. 5 Comorbidities and concurrent medications mask or complicate the clinical presentation. 2, 5 However, elderly patients have significantly higher perforation rates (18-70% vs 3-29% in younger patients), making accurate diagnosis essential. 4

Special Considerations for Immunocompromised Patients

Maintain an extremely low threshold for imaging in immunocompromised individuals, as they may not mount a normal inflammatory response. 2

• Order CT with IV contrast directly if clinical suspicion exists, bypassing ultrasound. 2
• Do not wait for laboratory abnormalities to develop. 4, 3
• Recognize that the absence of peritoneal signs does not exclude appendicitis in this population. 2

Clinical Risk Stratification

Use validated scoring systems to guide imaging decisions, not to exclude appendicitis:

• The Appendicitis Inflammatory Response (AIR) score has better diagnostic accuracy than the Alvarado score. 3
• Patients with intermediate risk based on clinical scores require systematic diagnostic imaging regardless of laboratory values. 3
• 8.4% of patients with confirmed appendicitis have low Alvarado scores (<5), demonstrating that scoring systems cannot exclude the diagnosis. 3

Key Physical Examination Findings to Document

Focus on peritoneal irritation signs rather than systemic inflammatory signs:

• Right lower quadrant tenderness with guarding (most consistent finding). 1
• Rovsing sign (left lower quadrant palpation causing right lower quadrant pain). 5
• Rebound tenderness at McBurney's point. 5
• In elderly patients, look for signs of peritonitis: abdominal distension, generalized tenderness, palpable mass. 2, 5

Common Pitfalls to Avoid

Anchoring bias on "classic presentation": The complete triad of migrating pain, fever, and leukocytosis is present in only a minority of patients. 5 Atypical presentations occur in approximately 50% of cases. 5

Delayed imaging in afebrile patients: Fever is present in only 30-80% of confirmed appendicitis cases, meaning 20-70% present without fever. 4 The absence of fever should never exclude appendicitis. 4

Over-reliance on ultrasound in obese patients: Obesity significantly reduces ultrasound accuracy, with false diagnosis rates of 34.4% in obese men versus 6.2% in non-obese men. 5 Proceed directly to CT in obese patients. 2

Negative appendectomy concerns in elderly: The complication rate for negative appendectomy is 25% in elderly patients versus 3% in younger patients, making pre-operative diagnostic accuracy critical. 2 This justifies aggressive imaging rather than conservative observation.

Laboratory Tests to Order (For Prognostic Value, Not Diagnosis)

While not diagnostic, order these tests for risk stratification and surgical planning:

• WBC with differential (neutrophil percentage >75% is the most sensitive individual marker at 82% sensitivity). 3
• CRP (values >101.9 mg/L in elderly patients suggest perforation). 2, 3
• Procalcitonin (AUC 0.94 for identifying complicated appendicitis). 2

Remember: Normal values do not exclude appendicitis. In elderly patients, unelevated WBC and CRP together showed 100% negative predictive value in one series, but this requires broader validation and should not prevent imaging when clinical suspicion exists. 3