<prompt> An 85-year-old woman hasa 48-hour history of generalized abdominal pain and vomiting. On examination, she is dehydrated multiple dilated small bowel loops measuring up to 4 cm in diameter. A linear gas-filled structure is present in the right upper quadrant with short branches extending from it. What is the most likely diagnosis?Acute mesenteric ischemiaEmphysematous cholecystitisGallstone ileusObstructed right inguinal hernia  <response>: Ans CSmall bowel obstruction in an elderly patient with evidence of pneumobilia is suggestive of Gall stone ileusQ. Imaging features of gall stone ileus are: Pneumobilia which appears as central branching air lucencies in the liver, small bowel obstruction and radiopaque density in the abdomen most common site of impaction is the terminal ileum. 