An experienced clinician looks for three linked features: infection, impaired bile flow, and inadequate perfusion. The complete classic pattern is Charcot's triad: - fever, often with rigors; - jaundice; and - right-upper-quadrant abdominal pain. The triad is highly specific when present, but it is a poor screening tool. Pooled sensitivity is only approximately 26–36%, with specificity around 96%. Therefore, a patient with fever and cholestatic jaundice but no right-upper-quadrant pain may still have acute cholangitis, particularly if imaging shows ductal obstruction. Absence of the full triad should lower confidence only modestly; it should not end the assessment. Reynolds' pentad adds hypotension and altered mental status to Charcot's triad. When these findings arise from cholangitis, they indicate suppurative infection with septic shock or imminent shock and require simultaneous resuscitation, antimicrobial therapy, and urgent drainage. The pentad appears in fewer than about 5% of cases, so its absence cannot reassure you that the illness is mild. Ask about prior biliary stones, pancreatitis, hepatobiliary surgery, ERCP, biliary stents, recurrent strictures, malignancy, and healthcare exposure. Determine when the pain, fever, jaundice, rigors, confusion, and...