Ultrasound
Increased liver echogenicity is in keeping with fatty infiltration with focal fat-sparing adjacent to the gallbladder fossa. Also adjacent to the gallbladder fossa is a focal region that is predominantly anechoic with multiple septations and no vascularity (segment 4a).
A calcified shadowing calculus is noted within the gallbladder neck/cystic duct and appears a little larger than on the CT, measuring up to 2 cm on ultrasound. Gallbladder wall appears thickened and slightly irregular although when measuring it, it is on the upper limits of normal. The gallbladder is mildly distended. There is no extrahepatic or intrahepatic bile duct dilatation. The patient certainly was not probed tender at Murphy's point but displayed generalised right-sided tenderness. I note the thickened and slightly narrowed appearance of the terminal ilium on the CT from earlier today, keeping the Crohn's disease. The appendix appears normal on the CT.
The spleen is normal. The pancreas is not well visualised due to overlying bowel gas.
Both kidneys were normal, with the hyperdense left renal lesion seen on CT not identified on ultrasound.
Conclusion
Ultrasound features are equivocal for acute calculus cholecystitis but this is still the most likely diagnosis given the patient's immunosuppression due to Crohn's disease. The hepatic lesion adjacent to the gallbladder in this context represents an abscess until proven otherwise.