The most likely diagnosis is choledocholithiasis. This patient's pain is consistent with biliary pain, and the presence of a transient elevation of serum alanine aminotransferase and the dilated bile ducts on ultrasound are consistent with intermittent biliary obstruction due to a common bile duct stone. Up to 20% of patients with symptomatic gallbladder stones will have a common bile duct stone. Although complications are more common than with symptomatic gallstones, less than 50% of patients with choledocholithiasis develop symptoms, and 20% spontaneously pass stones from the common bile duct. Assessment of the bile duct preoperatively with endoscopic ultrasound or magnetic resonance cholangiopancreatography is recommended if the clinical suspicion is high.

Acute pancreatitis could be a complication of a common bile duct stone, but the pain would not be intermittent and it would result in an elevated serum amylase level, which was not present in this patient.

A bile leak would present earlier, within a day or two after surgery. It would cause more continuous pain and would result in signs of peritonitis on examination. In addition, the bile ducts would not be dilated.

Fever suggests the development of cholangitis, which is potentially life threatening. Additional findings of cholangitis include jaundice and pain in the right upper quadrant (Charcot triad). Most patients will have cholelithiasis, elevated aminotransferase levels, and hyperbilirubinemia. Ultrasonography may show a dilated common bile duct.

Sphincter of Oddi dysfunction would produce the same symptoms as are found in this patient; however, this condition is typically diagnosed in patients with biliary-type pain without an alternative explanation. This patient's recent history of cholelithiasis, cholecystectomy, and dilated intrahepatic and extrahepatic bile ducts strongly suggests choledocholithiasis, not sphincter of Oddi dysfunction.