What testing should be done for a patient with right lower quadrant (RLQ) pain and fever after consuming beef and pork, with a history of lifting heavy at the gym, and no symptoms of diarrhea, urinary issues, vomiting, or nausea?

Diagnostic Testing for RLQ Pain with Fever After Heavy Lifting and Meat Consumption

Obtain a contrast-enhanced CT scan of the abdomen and pelvis immediately, as this is the primary diagnostic imaging modality for evaluating RLQ pain with fever, achieving sensitivities of 85.7-100% and specificities of 94.8-100% for identifying appendicitis and alternative pathologies. 1

Initial Clinical Assessment

Before imaging, perform a focused evaluation looking for:

• Migratory pain pattern: Ask specifically if pain started periumbilically and moved to RLQ, as this increases likelihood of appendicitis 1
• Psoas sign: Test for pain with hip extension or flexion, as a positive psoas sign suggests appendicitis or retroperitoneal pathology 1
• Rebound tenderness and guarding: These peritoneal signs significantly differentiate appendicitis from other causes of RLQ pain 1, 2
• Timing: Document exact onset relative to gym activity versus meat consumption, as the temporal relationship matters for differential diagnosis 1

Laboratory Testing

Order the following blood work immediately:

• Complete blood count with differential: White blood cell count and neutrophil percentage are significantly elevated in appendicitis compared to other causes of RLQ pain (p < 0.001) 2
• C-reactive protein: CRP levels are significantly higher in appendicitis versus other etiologies (p < 0.001), and normal inflammatory markers have 100% negative predictive value for excluding appendicitis 1, 2
• Basic metabolic panel: To assess for dehydration and electrolyte abnormalities if infection is present 1

Primary Imaging: CT Abdomen and Pelvis

CT with IV contrast (without oral contrast) is the definitive test, as it:

• Reduces negative appendectomy rates from 16.7% (clinical evaluation alone) to 8.7% 1
• Identifies alternative diagnoses including psoas abscess, mesenteric adenitis, diverticulitis, and infectious colitis 1, 3, 4
• Can be performed rapidly without delay from oral contrast administration, which is critical given fever suggesting possible perforation risk 1

The sensitivity of contrast-enhanced CT without enteral contrast ranges from 90-100% with specificity of 94.8-100% 1

Alternative Imaging Considerations

Ultrasound is NOT recommended as the initial test in this adult patient because:

• Appendix is not visualized in 27.7-45% of cases 1
• Even when visualized, sensitivity is only 51.8-81.7% in adults 1
• The negative appendectomy rate remains 38.4% when US is used for diagnosis 1

However, ultrasound may be considered first IF:

• The patient is young (under 30) and radiation exposure is a major concern 1
• CT is unavailable, with the understanding that negative or inconclusive US should be followed by CT 1

Critical Differential Diagnoses to Consider

Given the history of heavy lifting AND meat consumption with fever, the CT must evaluate for:

1. Appendicitis (most likely): Classic presentation with RLQ pain and fever 1

2. Psoas muscle strain/hematoma: Heavy lifting can cause psoas injury; look for psoas enlargement or fluid collection on CT 5

3. Infectious enterocolitis: Beef and pork consumption raises concern for Salmonella or other foodborne pathogens causing mesenteric adenitis, which presents identically to appendicitis with RLQ pain, fever, and leukocytosis 4

4. Typhlitis (if immunocompromised): Necrotizing colitis affecting the cecum, seen as colonic wall thickening on CT 3

Management Algorithm Based on CT Results

If appendicitis confirmed:

• Proceed to appendectomy as standard treatment 5
• For perforated appendicitis with abscess, consider percutaneous drainage followed by delayed surgery 5

If alternative diagnosis identified:

• Mesenteric adenitis: Symptomatic treatment, as this is typically self-limited, but obtain stool cultures given meat consumption history 4
• Psoas abscess: Immediate broad-spectrum antibiotics and percutaneous drainage for collections >3 cm 5

If CT is negative:

• Consider discharge with close follow-up if pain is mild and patient is clinically stable 2
• Admit for observation if pain is severe or clinical suspicion remains high despite negative imaging 1

Critical Pitfalls to Avoid

• Do not rely on clinical scoring systems alone: While Alvarado score may help exclude appendicitis, it should not be used to diagnose it, particularly given the atypical history of trauma and food exposure 1
• Do not delay imaging for oral contrast: This increases time to diagnosis and potentially increases perforation risk without improving diagnostic accuracy 1
• Do not assume appendicitis is the only diagnosis: The combination of trauma (heavy lifting) and potential food exposure requires broader differential consideration 5, 3, 4