A previously healthy 14-year-old girl was transferred to our facility from an outside hospital with a 10-day history of nausea, malaise, intermittent fever (peak 39.5°C), and fatigue. In the 72 hours prior to admission, she had developed progressive yellowing of the skin and scleral icterus. She had not traveled recently and her immunizations were up-to-date. She denied being sexually active or using illicit substances. She was a well-developed Caucasian adolescent who on initial presentation appeared fatigued and jaundiced. Vital signs on admission were the following: temperature, 38.8°C; heart rate, 96 beats per minute; respiratory rate, 18 breaths per minute; and blood pressure, 112/58 mm Hg. Her physical examination revealed scleral icterus, pharyngeal erythema with tonsillar exudates, anterior cervical lymphadenopathy, and right-sided abdominal tenderness. The liver edge was palpable at 1 cm below the right costal margin.Laboratory evaluation from the outside hospital revealed transaminase elevation and elevated serum bilirubin levels (Table 1). Complete blood count did not demonstrate evidence of anemia, thrombocytopenia, leukocytosis, or bandemia. Lipase level was normal at 32 U/L (23-300 U/L), though a C-reactive protein was mildly elevated at 1.20 mg/dL (<0.99 mg/ dL). Acetaminophen level was negative at <10.0 µg/ mL (10-25 µg/mL). Coagulation studies were within the reference range. An initial ultrasound of the abdomen showed diffuse thickening of the gallbladder wall, measuring up to 8.5 mm in thickness, with no evidence of biliary duct dilatation or the presence of stones (Figure 1). Splenomegaly was also seen. The patient did report right upper quadrant tenderness during the ultrasound, exhibiting the positive sonographic Murphy's sign. These findings were consistent with a working diagnosis of acute acalculous cholecystitis (AAC), and empiric broad-spectrum antibiotic therapy with piperacillin-tazobactam was initiated. All oral feeds were held and aggressive intravenous hydration was initiated.