What is the appropriate diagnosis and treatment for an 18-year-old male presenting with nausea, vomiting, abdominal pain, leukocytosis, neutrophilia, and hyperglycemia?

Acute Appendicitis with Possible Pyogenic Liver Abscess

This 18-year-old male with nausea, vomiting, abdominal pain, marked neutrophilia (88% neutrophils, absolute count 9.73), lymphopenia (6%, absolute 0.63), and mild hyperglycemia most likely has acute appendicitis, though pyogenic liver abscess must be urgently excluded given the laboratory pattern. 1, 2

Diagnostic Approach

Laboratory Interpretation

The laboratory findings are highly characteristic of acute bacterial infection requiring urgent surgical evaluation:

• Marked neutrophilia (88%) with absolute neutrophil count of 9.73 is the hallmark of acute bacterial infection, particularly intra-abdominal pathology 1, 3
• Severe lymphopenia (6%, absolute 0.63) combined with neutrophilia has 94.9% specificity for severe infectious or surgical illness requiring intervention 3
• The combination of neutrophil count >9.0 × 10⁹/L with lymphopenia (<1.4 × 10⁹/L) predicts surgical/infectious pathology with very high specificity, though sensitivity is only 27.5% 3
• Mild hyperglycemia (116 mg/dL) represents stress response to acute infection 4

Immediate Imaging Required

CT abdomen and pelvis with IV contrast is the single most important diagnostic test and should be obtained immediately 1, 2:

• CT has 85.7-100% sensitivity and 94.8-100% specificity for appendicitis in adults with classic presentation (fever, leukocytosis, RLQ pain) 1
• CT will simultaneously evaluate for pyogenic liver abscess, which presents with persistent fever, epigastric/RUQ pain, nausea, and marked leukocytosis (often >20,000) 2
• The negative appendectomy rate with preoperative CT is only 1.7-7.7% versus 16.7% with clinical evaluation alone 1

If CT is unavailable or contraindicated, right upper quadrant ultrasound should be obtained first to exclude liver abscess, followed by focused appendiceal ultrasound 2, 4:

• Ultrasound has >90% sensitivity for liver abscess and can guide percutaneous drainage 2
• Appendiceal ultrasound has 81.7% sensitivity and 53.9% specificity when the appendix is visualized, but non-visualization occurs in 27.7-45% of cases 1

Critical Blood Work Before Antibiotics

Obtain at least 2 sets of blood cultures immediately before starting antibiotics 2:

• Blood cultures are positive in approximately 70% of pyogenic liver abscesses (Klebsiella pneumoniae, E. coli, anaerobes) 2
• Blood cultures are rarely positive in uncomplicated appendicitis but help differentiate from systemic bacteremia 1

Differential Diagnosis Priority

Most Likely: Acute Appendicitis

Appendicitis is the leading diagnosis given the classic triad of fever, leukocytosis, and presumed RLQ pain in a young male 1:

• The "classic" presentation (periumbilical pain migrating to RLQ, anorexia, nausea/vomiting, fever, leukocytosis) occurs in only 50% of patients 1
• Approximately 50% of appendicitis patients present with atypical features, making imaging mandatory 1
• Neutrophilia with lymphopenia is characteristic of surgical abdominal pathology 3

Must Exclude: Pyogenic Liver Abscess

Pyogenic liver abscess must be urgently excluded because the laboratory pattern (marked leukocytosis, nausea, vomiting) is highly characteristic 2:

• Fever pattern that fluctuates but never normalizes over 3 days is classic for intra-abdominal abscess 2
• Marked leukocytosis (this patient has 11.1, but neutrophil predominance suggests bacterial infection) strongly suggests bacterial infection rather than viral hepatitis 2
• Mildly elevated transaminases would be consistent with liver abscess (though not reported here), whereas acute viral hepatitis causes markedly elevated transaminases 2

Less Likely Considerations

Neutropenic enterocolitis is excluded because this patient has leukocytosis, not neutropenia 1, 5:

• Neutropenic enterocolitis (typhlitis) occurs in chemotherapy patients with neutropenia, presenting with fever, abdominal pain, nausea, vomiting, and diarrhea 1, 5
• This diagnosis requires neutropenia as a prerequisite 5

COVID-19 enterocolitis is unlikely given the absence of respiratory symptoms and the marked neutrophilia rather than lymphocytosis 1:

• COVID-19 GI manifestations include diarrhea (8-37%), nausea (1-25%), vomiting (2-8%), and abdominal pain (0.3-17%) 1
• COVID-19 typically causes lymphopenia but not this degree of neutrophilia 1

Treatment Algorithm

If Appendicitis Confirmed on Imaging

Proceed to appendectomy within 24 hours of diagnosis 1:

• Laparoscopic appendectomy is preferred whenever feasible 1
• Early surgical intervention (within 24 hours) prevents progression to perforation, which occurs in 8.2% of cases and significantly increases morbidity 1
• Preoperative antibiotics should cover Gram-negative and anaerobic bacteria 1

If Pyogenic Liver Abscess Confirmed

Start empiric IV antibiotics immediately: ceftriaxone 2g IV daily PLUS metronidazole 500mg IV every 8 hours 2:

• This regimen covers Gram-positive, Gram-negative, and anaerobic bacteria with high response rate within 72-96 hours 2
• Continue IV antibiotics for the full 4-week duration rather than transitioning to oral therapy to prevent readmission 2

Percutaneous catheter drainage is first-line for abscesses >4-5 cm 2:

• Combined with antibiotics, drainage has 83% success rate for large unilocular abscesses 2
• Aspiration cultures should be obtained to guide targeted antibiotic therapy 2

If Both Diagnoses Excluded

Broaden differential to include other causes of acute abdomen with neutrophilia 4:

• Consider pancreatitis (check serum lipase >3× upper limit of normal) 4
• Consider cholecystitis (RUQ ultrasound has >90% sensitivity) 4
• Consider perforated viscus (upright chest X-ray for free air) 1

Critical Pitfalls to Avoid

Do not delay imaging in favor of clinical observation alone 1, 2:

• The negative appendectomy rate without imaging is 16.7% versus 1.7-7.7% with CT 1
• Delayed diagnosis of liver abscess increases risk of rupture, sepsis, and death 2

Do not start oral antibiotics without source control 2:

• Oral antibiotics are inadequate for pyogenic liver abscess and increase readmission risk 2
• Appendicitis requires surgical intervention, not antibiotics alone 1

Do not miss the underlying source of infection 2:

• Biliary obstruction may require ERCP with sphincterotomy if present 2
• Every verified source of infection must be controlled to prevent recurrence 2