A 68-year-old man is admitted to the ICU following a major cardiac surgery. On postoperative day 5, while on mechanical ventilation and TPN support, he develops unexplained fever (38.5°C), leukocytosis (WBC 14,500/μL), and elevated liver enzymes. Bedside ultrasound is performed. The structure marked **A** in the diagram shows a distended thick-walled gallbladder with pericholecystic fluid but no gallstones. Which of the following is the most likely diagnosis and the primary reason for the high mortality in this condition?

Explanation

## Why option 1 is right The ultrasound findings of a distended thick-walled gallbladder with pericholecystic fluid and **no gallstones** in a critically ill ICU patient on TPN with unexplained sepsis is pathognomonic for acute acalculous cholecystitis (AAC). According to Tokyo Guidelines 2018, AAC accounts for 5–10% of acute cholecystitis but carries a much higher mortality (30–50% vs 1–5% for calculous disease) because it occurs in critically ill patients and is frequently delayed in diagnosis. The pathophysiology involves biliary stasis from TPN-induced loss of CCK-mediated emptying, gallbladder ischemia from low cardiac output and sepsis, and bacterial superinfection (E. coli, Klebsiella, anaerobes). The combination produces inflammation, gangrene in 50%, and perforation in up to 10%, explaining the high mortality. Early diagnosis and intervention (percutaneous cholecystostomy or cholecystectomy) are critical. ## Why each distractor is wrong - **Option 2**: Acute calculous cholecystitis with spontaneous stone passage is extremely rare and would not explain the pericholecystic fluid and wall thickening on ultrasound. Moreover, the clinical context (ICU, TPN, unexplained sepsis) is classic for AAC, not stone disease. - **Option 3**: Biliary dyskinesia is a functional disorder without structural inflammation, wall thickening, or pericholecystic fluid. It does not present with fever, leukocytosis, or sepsis and is not a surgical emergency. - **Option 4**: Gallbladder carcinoma is a chronic malignancy that does not present acutely with fever and sepsis in the immediate postoperative period. The clinical presentation and risk factors (ICU, TPN, cardiac surgery) are entirely inconsistent with malignancy. **High-Yield:** Acalculous cholecystitis in ICU patients on TPN or after major surgery is a surgical emergency with 30–50% mortality; diagnosis requires high clinical suspicion and ultrasound showing wall thickening >3.5–4 mm, pericholecystic fluid, and distension WITHOUT stones; percutaneous cholecystostomy is first-line in unstable patients. [cite: Tokyo Guidelines 2018 for Acute Cholecystitis]