What are the guidelines for assessing and managing suspected appendicitis?

Assessment and Management of Suspected Appendicitis

Initial Clinical Assessment

Begin with focused evaluation for characteristic findings: right lower quadrant pain with migration from periumbilical region, fever, and signs of peritoneal irritation (rebound tenderness, guarding, rigidity). 1, 2

Key Clinical Discriminators

• Right lower quadrant pain, abdominal rigidity, and periumbilical pain radiating to the right lower quadrant are the strongest clinical predictors in adults 3
• In children, prioritize assessment for absent/decreased bowel sounds, positive psoas sign, positive obturator sign, and positive Rovsing sign 3
• Migration of pain to the right lower quadrant, fever, and positive psoas sign increase likelihood of appendicitis 4
• Vomiting occurring before pain onset makes appendicitis less likely 4

Laboratory Testing

• Obtain white blood cell count with differential, C-reactive protein, and granulocyte count 1, 5
• Inflammatory markers (elevated WBC, neutrophil percentage, CRP) are strong discriminators with ROC areas of 0.78-0.85, particularly for perforated appendicitis 5
• Appendicitis is very unlikely when all three markers (WBC, neutrophil percentage, CRP) are simultaneously normal - only 6 of 740 patients with confirmed appendicitis had all three normal 6
• Individual markers have limited utility (sensitivity 76-88%, specificity 26-34%), but combined abnormalities significantly increase diagnostic accuracy 6

Diagnostic Imaging Strategy

Adults (Non-Pregnant)

Obtain CT abdomen and pelvis with IV contrast as the initial imaging modality - this achieves sensitivity of 96-100% and specificity of 93-95%. 1, 2, 4

• IV contrast is strongly preferred as it increases sensitivity to 96% compared to unenhanced CT 1, 4
• Oral contrast is not necessary and may delay diagnosis without improving accuracy 4
• CT without IV contrast remains acceptable if IV contrast is contraindicated, maintaining high diagnostic accuracy 1

Children and Adolescents

Start with ultrasound as the initial imaging modality to avoid radiation exposure (sensitivity 76%, specificity 95%). 1, 2, 4

• If ultrasound is equivocal/non-diagnostic and clinical suspicion persists, proceed to MRI or CT rather than repeating ultrasound 1
• When CT is performed after equivocal ultrasound, use IV contrast (CT without IV contrast may be appropriate in select cases) 1
• Observation may be appropriate instead of subsequent imaging depending on clinical context 1
• If strong clinical suspicion persists after equivocal imaging, consider exploratory laparoscopy/laparotomy if further imaging would delay appropriate management 1

Common pitfall: Ultrasound is highly operator-dependent with 36% median rate of equivocal results in children (range 3-75%) 1, 4

Pregnant Patients

Obtain ultrasound as the initial imaging modality. 1, 2, 4

• All female patients of childbearing potential should undergo pregnancy testing prior to imaging 1
• If ultrasound is inconclusive, proceed to MRI without IV contrast rather than CT to avoid ionizing radiation 1, 2, 4
• First trimester patients should avoid CT; use ultrasound or MRI 1, 2
• MRI achieves sensitivity of 94% and specificity of 96% for acute appendicitis 4

Critical consideration: 95% median rate of equivocal ultrasound results in pregnant patients necessitates low threshold for MRI 1

Management Based on Imaging Results

Positive Imaging

Initiate broad-spectrum antibiotics immediately covering aerobic gram-negative organisms and anaerobes once appendicitis is diagnosed or strongly suspected. 4

• Perform appendectomy as soon as reasonably feasible - both laparoscopic and open approaches are acceptable 4
• Laparoscopic approach is preferred in children 4
• Large periappendiceal abscess or phlegmon may warrant percutaneous drainage rather than immediate appendectomy 4

Negative Imaging with Persistent Clinical Suspicion

Consider observation and supportive care, with or without antibiotics; if clinical suspicion is very high, consider surgical intervention despite negative imaging. 1

• Follow-up at 24 hours is mandatory to ensure resolution of signs and symptoms due to low but measurable risk of false-negative results 1, 2
• Investigate extra-abdominal sources of infection and non-infectious inflammatory conditions 1

Equivocal Imaging

Careful follow-up is required for patients with suspected appendicitis that cannot be confirmed or excluded by imaging. 1

• Hospital or emergency department observation may be necessary to evaluate symptom evolution 2
• Consider repeat imaging or surgical consultation based on clinical trajectory 2

Clinical Pathway Implementation

Hospitals should establish standardized clinical pathways involving surgeons, infectious diseases specialists, emergency physicians, radiologists, nursing providers, and pharmacists to ensure comprehensive management from presentation through discharge. 1, 2

These pathways should reflect local resources and standards of care 1

Special Populations

• Pregnant women require timely surgical intervention to decrease complications 2
• Immunocompromised patients should undergo timely surgical intervention 2
• Elderly patients should receive CT with IV contrast given higher rates of complicated appendicitis and mortality 4
• Children aged <3 years should undergo diagnostic imaging when diagnosis is uncertain 2

Critical Pitfalls to Avoid

• Do not proceed directly to appendectomy without imaging in patients with incomplete clinical findings - this risks unnecessary surgery (negative appendectomy carries long-term morbidity) and missing alternative diagnoses 4
• Low or incomplete Alvarado scores do not reliably exclude appendicitis - 8.4% of patients with appendicitis had scores below 5 4
• Both MRI and ultrasound may incorrectly classify up to half of patients with perforated appendicitis as having simple appendicitis 4