What is the most likely diagnosis and recommended acute management for a patient presenting with acute abdominal pain, leukocytosis of 17.8 ×10⁹/L with neutrophilia, C‑reactive protein of 65 mg/L, and elevated bilirubin?

Acute Abdominal Pain with Leukocytosis, Neutrophilia, Elevated CRP, and Hyperbilirubinemia

The most likely diagnoses are acute cholecystitis, acute cholangitis, or complicated intra-abdominal infection requiring immediate CT imaging with IV contrast, broad-spectrum antibiotics, and urgent surgical consultation.

Immediate Diagnostic Workup

Obtain contrast-enhanced CT abdomen/pelvis with IV contrast immediately – this is the definitive diagnostic test with 95% sensitivity and 94% specificity for surgical causes of acute abdomen and is mandatory in this clinical scenario 1. Plain radiographs have only 25% sensitivity and should not delay CT imaging 1.

Critical Laboratory Assessment

Beyond the already obtained values, complete the following:

• Serum lactate – essential marker for bowel ischemia or sepsis 1
• Procalcitonin – higher diagnostic accuracy than CRP alone for bacterial sepsis 2
• Blood cultures – obtain before antibiotics if fever present 1
• Liver function panel – AST, ALT, alkaline phosphatase, and direct/indirect bilirubin to characterize the hyperbilirubinemia pattern 2
• Coagulation studies – PT/INR given elevated bilirubin 2

Interpretation of Current Laboratory Values

The combination of WBC 17.8 with neutrophilia, CRP 65 mg/L, and elevated bilirubin creates a highly specific pattern:

• CRP >50 mg/L has 87.5% sensitivity and 91.1% specificity for severe intra-abdominal pathology 2. Your patient's CRP of 65 mg/L significantly exceeds this threshold.
• CRP has remarkably higher sensitivity and specificity than WBC or neutrophil count alone for ruling in abdominal surgical disease 2.
• The triad of neutrophilia (>9.0 × 10⁹/L), lymphopenia (<1.4 × 10⁹/L), and eosinopenia (<0.04 × 10⁹/L) has 94.9% specificity for severe illness requiring surgical intervention 3.
• Elevated bilirubin with inflammatory markers strongly suggests biliary pathology (cholecystitis, cholangitis, choledocholithiasis) or hepatic involvement in sepsis 2.

Most Likely Differential Diagnoses

Primary Considerations:

1. Acute cholecystitis with possible cholangitis – the elevated bilirubin is the key distinguishing feature
2. Complicated diverticulitis with abscess – if pain is left lower quadrant 2, 4
3. Perforated viscus with peritonitis – if diffuse peritoneal signs present 2
4. Appendicitis with perforation/abscess – if right lower quadrant pain 1

Critical Pitfall to Avoid:

Do not assume normal CRP rules out serious pathology – while your patient has elevated CRP, be aware that normal CRP does not exclude early appendicitis or postoperative complications 2, 1, 5. However, CRP ≥5 mg/dL has high specificity for intra-abdominal pathology, and your patient's value of 65 mg/L is 13-fold higher, making serious pathology highly likely 1.

Immediate Management Algorithm

Step 1: Resuscitation and Stabilization

• NPO status immediately 4
• IV fluid resuscitation – correct dehydration and third-spacing 4
• Obtain blood cultures before antibiotics if not already done 1

Step 2: Empiric Broad-Spectrum Antibiotics

Start antibiotics immediately after blood cultures – do not wait for imaging if signs of sepsis (fever, hypotension, tachycardia) are present 1, 6.

Recommended regimens:

• First-line: Piperacillin-tazobactam 3.375-4.5g IV every 6 hours 6, 4
• Alternative: Ceftriaxone 1-2g IV daily PLUS Metronidazole 500mg IV every 8 hours 1
• Alternative: Ertapenem 1g IV daily 4

These regimens cover gram-negative enteric organisms, gram-positive organisms, and anaerobes 6, 4.

Step 3: Urgent Surgical Consultation

Contact surgery immediately, even while pursuing medical management 6. The combination of leukocytosis, elevated CRP, and hyperbilirubinemia warrants early surgical involvement regardless of imaging findings 2, 6.

Step 4: CT Imaging Interpretation

Once CT is obtained, look for:

• Biliary tree dilation, gallbladder wall thickening, pericholecystic fluid – suggests cholecystitis/cholangitis
• Bowel wall thickening >10mm – associated with 60% mortality risk in certain populations 2
• Free air or distant gas – indicates perforation requiring immediate surgery 2
• Abscess formation – abscesses ≥4cm typically require percutaneous drainage 2
• Fat stranding and fluid collections – indicates complicated disease 2, 4

Monitoring and Escalation Criteria

Serial Assessment Requirements:

• Vital signs every 2-4 hours – tachycardia is the most sensitive sign of deterioration 2
• Serial abdominal examinations – worsening peritoneal signs mandate surgical exploration 6, 4
• Repeat CRP at 48-72 hours – rising CRP despite antibiotics suggests abscess or inadequate source control 1, 4

Absolute Indications for Emergency Surgery:

• Signs of perforation (free air, diffuse peritonitis) 2, 6
• Bowel ischemia (elevated lactate, clinical deterioration) 1, 6
• Hemodynamic instability despite resuscitation 2
• Clinical deterioration despite 48-72 hours of appropriate antibiotics 6, 4

Special Considerations

If Biliary Pathology Confirmed:

• Cholecystitis: Early cholecystectomy (within 72 hours) reduces morbidity
• Cholangitis: Requires urgent ERCP for biliary decompression in addition to antibiotics
• Choledocholithiasis: May require ERCP before or during cholecystectomy

If Patient Has History of Bariatric Surgery:

Tachycardia is the most sensitive warning sign of surgical complications 2. The combination of fever, tachycardia, and tachypnea predicts anastomotic leak or internal hernia 2. Do not delay surgical exploration in this population as clinical signs are often subtle 2.

Expected Clinical Course:

• Clinical improvement should occur within 3-5 days of appropriate antibiotics 1
• If no improvement by 48-72 hours, repeat imaging to assess for abscess or inadequate source control 1, 4
• If adequately drained infection identified, 5 days of antibiotics is sufficient rather than 10 days 1

Critical Pitfalls to Avoid

1. Never delay CT imaging based on "reassuring" physical examination – clinical signs are unreliable, especially in obese patients or those with prior surgery 2, 6

2. Never assume viral gastroenteritis with WBC 17.8 – this degree of leukocytosis warrants exclusion of surgical pathology 1

3. Never use ultrasound alone instead of CT – CT is the definitive study with superior sensitivity and specificity 1

4. Never delay surgical consultation – early involvement is essential given the high mortality of missed surgical disease 2, 6

5. Never rely on normal CRP to rule out pathology (though not applicable here) – it does not exclude early appendicitis or postoperative complications 2, 1, 5