Review Question - QID 214340

A 44-year-old woman presents to the emergency department with abdominal pain. This symptom started yesterday and has been gradually worsening. The patient has a past medical history of acute cholecystitis and had her gallbladder removed 1 month ago. Her temperature is 97.7°F (36.5°C), blood pressure is 144/84 mmHg, pulse is 89/min, respirations are 12/min, and oxygen saturation is 98% on room air. Physical exam is notable for right upper quadrant tenderness to palpation. An ultrasound is performed demonstrating a dilated common bile duct and an absence of a gallbladder. Laboratory studies are ordered as seen below.

Hemoglobin: 13 g/dL
Hematocrit: 37%
Leukocyte count: 9,500/mm^3 with normal differential
Platelet count: 168,000/mm^3

Serum:
Na+: 139 mEq/L
Cl-: 100 mEq/L
K+: 4.8 mEq/L
HCO3-: 25 mEq/L
BUN: 23 mg/dL
Glucose: 99 mg/dL
Creatinine: 1.2 mg/dL
Ca2+: 10.2 mg/dL
AST: 82 U/L
ALT: 100 U/L
Alkaline phosphatase: 250 U/L

Which of the following is the most appropriate next step in management?