A 45-year-old Indian woman presents with chronic diarrhea, weight loss, and abdominal bloating for 6 months. She has a history of celiac disease diagnosed 2 years ago but poor dietary compliance. On small bowel follow-through (SBFT), the structure marked **A** in the left upper quadrant shows loss of its characteristic feathery appearance with prominent valvulae conniventes, and instead displays a smooth, featureless tubular pattern similar to the ileum. Which of the following radiological findings best explains this change in the jejunal mucosal pattern?