A 48-year-old female undergoes a segmentectomy for a focal nodular hyperplasia in segment IV. Which major vascular structure forms the superior boundary of Couinaud's segment IV?

A rural farmer presents with abdominal pain. Ultrasound shows a large liver cyst with daughter vesicles. What is the most likely infective agent?

A 35-year-old male is diagnosed with an amoebic liver abscess, measuring 6.5 cm, located in the subcapsular region of the left hepatic lobe. Despite 48 hours of high-dose intravenous metronidazole, his pain is worsening, and he develops localized peritonitis signs. What is the immediate surgical intervention indicated?

A 70-year-old male with a history of recurrent cholangitis presents with severe sepsis. Imaging reveals a large common bile duct stone causing complete obstruction. He is deemed high-risk for ERCP due to comorbidities. Considering the immediate need for biliary decompression in this critically ill patient, what would be the most appropriate alternative surgical intervention?

During a laparoscopic cholecystectomy for symptomatic cholelithiasis, the surgeon encounters significant inflammation and scarring in Calot's triangle. To ensure patient safety and prevent iatrogenic injury, which of the following structures is most critical to definitively identify before clip application and division?

Following a difficult cholecystectomy, a patient develops persistent right upper quadrant pain, fever, and a rising bilirubin 7 days post-surgery. MRCP shows a partial transection of the common hepatic duct with an associated biloma. Which Strassberg classification best describes this injury?

What is a key distinguishing principle of the BCLC staging system for HCC compared to TNM staging?

A 62-year-old male presents with a 3-week history of painless jaundice, pruritus, and significant weight loss. Physical examination reveals a palpable, non-tender gallbladder. Which of the following is the most likely diagnosis?

A 52-year-old woman presents with a 4-month history of a painful, pruritic rash. The rash began in the groin and has now spread to her lower legs. Examination reveals erythematous plaques with central blistering, crusting, and superficial erosions. She was also recently diagnosed with type 2 diabetes mellitus and reports feeling unusually low in mood. Her HbA1c is 8.5%, and a complete blood count is normal. What is the most likely underlying diagnosis?