What is the likely diagnosis and recommended work‑up and initial treatment for a patient presenting with right‑upper‑quadrant pain, fever, leukocytosis and possible jaundice, possibly due to gallstones?

Acute Cholangitis (Ascending Cholangitis)

The most likely diagnosis is acute cholangitis, and you should immediately initiate broad-spectrum IV antibiotics, obtain urgent ultrasound to confirm biliary obstruction, and arrange emergent ERCP for biliary decompression within 24-48 hours. 1

Clinical Diagnosis

The presentation of right upper quadrant pain, fever, leukocytosis, and jaundice in a patient with suspected gallstones represents Charcot's triad (fever/chills, jaundice, RUQ pain), which is pathognomonic for acute cholangitis. 1 This is a biliary emergency requiring urgent intervention, as the mortality rate increases significantly with delayed treatment. 1

Immediate Diagnostic Work-Up

First-Line Imaging

• Obtain right upper quadrant ultrasound immediately as the initial diagnostic test (rated 9/9 by ACR for appropriateness). 1, 2
• Ultrasound will identify cholelithiasis with 96% accuracy and can demonstrate bile duct dilatation, which is the critical finding supporting cholangitis. 1
• Look specifically for common bile duct diameter >6mm (or >8mm if post-cholecystectomy), gallstones, and intrahepatic ductal dilatation. 1

Essential Laboratory Tests

• Complete blood count to document leukocytosis (typically >10,000/μL). 1, 3
• Comprehensive metabolic panel including bilirubin (typically elevated >22.23 μmol/L), alkaline phosphatase, GGT, ALT, and AST to confirm cholestatic pattern. 1, 3
• Blood cultures before antibiotic administration, as bacteremia is present in 20-70% of cases. 1
• Pregnancy test (beta-hCG) in all women of reproductive age before any imaging. 3, 4

Second-Line Imaging (If Ultrasound Equivocal)

• MRCP is superior to CT for evaluating suspected biliary obstruction, with 85-100% sensitivity for choledocholithiasis versus only 75% for CT. 1, 2
• MRCP should be obtained if ultrasound shows bile duct dilatation but no clear stone, or if clinical suspicion remains high despite negative ultrasound. 1, 2
• Never order CT without IV contrast for suspected cholangitis—critical findings like gallbladder wall enhancement and liver parenchymal hyperemia cannot be detected without contrast. 1, 2

Immediate Treatment Algorithm

Antibiotic Therapy

• Initiate broad-spectrum IV antibiotics immediately upon clinical suspicion, without waiting for imaging confirmation. 1
• Cover gram-negative organisms (E. coli, Klebsiella) and anaerobes with piperacillin-tazobactam or a carbapenem. 1

Biliary Decompression

• Arrange urgent ERCP within 24-48 hours for patients with acute cholangitis and confirmed biliary obstruction. 1
• ERCP allows both diagnostic confirmation and therapeutic stone extraction with sphincterotomy. 1
• Patients with septic shock or mental status changes require emergent ERCP within 12 hours. 1

Surgical Consultation

• Obtain immediate surgical consultation, as some patients may require percutaneous transhepatic biliary drainage if ERCP fails or is unavailable. 1
• Cholecystectomy should be performed after resolution of acute cholangitis, typically during the same hospitalization. 1

Critical Pitfalls to Avoid

• Do not assume normal ultrasound excludes cholangitis—ultrasound has only 73% sensitivity for detecting common bile duct stones. 1 If clinical suspicion is high (fever + jaundice + RUQ pain), proceed to MRCP or EUS. 1
• Do not delay antibiotics waiting for imaging—mortality increases with delayed treatment, and antibiotics should be started based on clinical presentation alone. 1
• Do not leave small stones (<4mm) untreated—even stones <4mm have a 15.9% risk of unfavorable outcomes (pancreatitis, cholangitis, obstruction) if left in situ versus 8.9% with extraction. 1
• Recognize that 25.3% of patients with untreated common bile duct stones develop complications versus only 12.7% with planned stone extraction (OR 0.44). 1

When Cholecystitis vs. Cholangitis Is Unclear

• Cholecystitis presents with RUQ pain, fever, and positive Murphy's sign but typically without jaundice or significant bilirubin elevation. 1
• Cholangitis requires the triad of jaundice, fever/chills, and RUQ pain plus laboratory evidence of biliary stasis (elevated bilirubin, alkaline phosphatase) and imaging showing biliary dilatation. 1, 2
• If jaundice is present with fever and RUQ pain, cholangitis takes diagnostic priority and requires more urgent intervention than cholecystitis alone. 1