On what is the diagnosis based?
Acute cholangitis is diagnosed based on systemic signs of inflammation (fever, leukocytosis, ↑ CRP) in combination with signs of cholestasis (jaundice, ↑ GGT, ↑ ALP) and/or characteristic imaging findings (e.g., dilated CBD, periductal inflammation). Once the diagnosis is confirmed, disease severity should be assessed to determine the best approach to management
What is not included in the diagnostic criteria?
Charcot triad is not included in the diagnostic criteria because, although specific, it is not a sensitive criterion and may even be absent in patients with acute cholangitis.
What are lab. tests that support the clinical diagnosis?
CBC: leukocytosis with left shift
LFTs: signs of cholestasis (↑ bilirubin, ↑ GGT, ↑ ALP, ↑ALT)
Blood cultures (2 sets): obtain before administering antibiotics (especially in febrile patients). 
Bile cultures: obtain during biliary drainage procedure
List tests to asess the severity of disease.
Blood gas analysis: PaO2/FiO2 ratio < 300 in severely ill patients
BMP: AKI, electrolyte derangements in patients with severe disease
PT/INR: coagulopathy in patients with severe disease
List tests to evaluate differential diagnoses.
Consider serum lipase levels to assess for concurrent biliary pancreatitis in patients with suspected common bile duct obstruction.
When are atypical presentations more common?
Atypical presentations are common in elderly patients. Consider obtaining liver chemistries to evaluate for acute cholangitis in acutely ill elderly patients with nonspecific symptoms.
What is the goal of imaging?
Acute cholangitis cannot be diagnosed with imaging alone. The goal of imaging is to evaluate for biliary obstruction that may have precipitated cholangitis.
Describe the indication and supportive findings of RUQ ultrasound.
Indication: preferred first-line imaging modality in patients presenting with suspected cholangitis
Dilated common bile duct
Dilated intrahepatic bile ducts: indicates obstructive cholestasis
Thickened bile duct walls
Evidence of underlying etiology, such as:
Choledocholithiasis: occluding CBD stone with/without cholelithiasis may be visualized
Biliary stricture: focal narrowing of the bile duct(s), with dilation of the proximal biliary tree
Biliary tumor: intraluminal mass within the bile duct
Describe the indications and supportive findings of CT scan with IV contrast.
Confirmatory imaging modality if ultrasound is inconclusive
To rule out differential diagnoses if the clinical diagnosis is unclear
Concentric thickening and heterogeneous enhancement of the walls of the biliary tree
Bile duct dilation
Evidence of underlying cause: choledocholithiasis, biliary tumor , biliary-enteric fistula, hydatid cyst, etc.
Evidence of complications: pericholecystic or liver abscess, portal vein thrombosis.
Describe the MRI abdomen +/- IV contrast with MRCP
Indication: an alternative confirmatory imaging modality if ultrasound is inconclusive
Supportive findings: similar to CT findings
List DDs for RUQ pain with fever with/withour jaundice.
Acute calculus cholecystitis or its complications
Bile leak (iatrogenic, e.g., post-ERCP, postcholecystectomy)
Acute necrotizing pancreatitis
Gall bladder cancer
Carcinoma head of the pancreas