How do you diagnose appendicitis with signs and symptoms?

Diagnosing Appendicitis with Signs and Symptoms

The diagnosis of appendicitis should not be based solely on clinical signs and symptoms but requires a tailored approach combining clinical assessment, laboratory tests, and appropriate imaging studies for accurate diagnosis and to reduce morbidity and mortality.1

Clinical Presentation

• Right lower quadrant pain, abdominal rigidity, and periumbilical pain radiating to the right lower quadrant are the most reliable signs for diagnosing acute appendicitis in adults 2
• The classic triad of migrating right lower quadrant pain of short duration, fever, and leukocytosis is present in approximately 50% of patients with appendicitis 3
• Tenderness in the right lower quadrant, nausea, and vomiting are common symptoms 1
• Positive psoas sign, fever, or migratory pain to the right lower quadrant increases the likelihood of appendicitis 1
• Conversely, vomiting before pain makes appendicitis less likely 1
• In elderly patients, presentation may include signs and symptoms consistent with ileus or bowel obstruction and more signs of peritonitis (abdominal distension, generalized tenderness and guarding, rebound tenderness, palpable abdominal mass) 1

Laboratory Evaluation

• Laboratory tests should always be requested as part of the diagnostic workup 1
• White blood cell count is often elevated (>10,000/mm³) with a positive likelihood ratio of 2.47 for appendicitis 3
• For WBC counts >15,000/mm³, the positive likelihood ratio increases to 3.47 3
• C-reactive protein (CRP) combined with leukocytosis provides better diagnostic accuracy than either test alone 3
• Normal leukocyte count and CRP values together have a 100% negative predictive value for appendicitis 1
• Procalcitonin has significant diagnostic value for identifying complicated appendicitis 1

Clinical Scoring Systems

• The Alvarado score, Appendicitis Inflammatory Response (AIR) score, and Adult Appendicitis Score (AAS) help stratify patients into low, moderate, or high risk categories 1
• AIR and AAS scores currently have the highest discriminating power in adults with suspected appendicitis 1
• These scores can reduce negative appendectomy rates in low-risk groups and decrease the need for imaging studies 1
• In elderly patients, Alvarado score with a cut-off of 5 maintains reliability, with most confirmed cases scoring between 5-8 1

Imaging Studies

• Helical CT of the abdomen and pelvis with intravenous contrast (not oral or rectal) is the recommended imaging procedure for patients with suspected appendicitis 1
• CT has higher sensitivity (90.8%) and specificity (94.2%) compared to ultrasound 4
• Ultrasound should be considered as first-line imaging in children and pregnant women to avoid radiation exposure 5
• MRI shows excellent diagnostic performance with high sensitivity (94%) and specificity (96%) and is recommended for pregnant patients when ultrasound is inconclusive 1, 5

Diagnostic Algorithm

1. Assess clinical signs and symptoms (right lower quadrant pain, fever, nausea/vomiting)
2. Perform laboratory tests (WBC count, CRP)
3. Calculate clinical score (Alvarado, AIR, or AAS)
4. Based on risk stratification:
   • Low risk: Observation may be appropriate
   • Intermediate risk: Proceed to imaging
   • High risk: Surgical consultation and appropriate imaging
5. Select imaging modality:
   • Adults: CT with IV contrast
   • Children/pregnant women: Ultrasound first, followed by MRI or low-dose CT if inconclusive

Special Considerations

• Elderly patients have a lower rate of correct pre-operative diagnosis and longer time from symptom onset to treatment 1
• In pregnant patients, diagnosis should never be based on symptoms and signs alone; laboratory tests and imaging are essential 1
• For children, especially those under 3 years, imaging is recommended when the diagnosis is uncertain 1
• Patients with equivocal imaging findings but persistent symptoms may still benefit from diagnostic laparoscopy 6

Common Pitfalls

• Relying solely on clinical signs and symptoms or laboratory tests for diagnosis, especially in elderly patients 1
• Delaying surgical consultation in moderate to high-risk patients, which increases the risk of perforation 2
• Overlooking appendicitis in patients with atypical presentations, particularly in elderly patients, pregnant women, and children 7
• Failing to recognize that perforation risk increases with prolonged duration of symptoms before intervention 2