The small intestine appears as a series of tubular structures within the abdomen on CT scans. 1. Wall Thickness: A normal small bowel wall is typically thin, measuring less than 3 mm in thickness. 2. Lumen: The lumen (inner space) is usually collapsed or slit-like in the absence of fluid or gas. When distended, it appears as a round or oval structure. 3. Contents: The small intestine normally contains gas and fluid, but excessive amounts can indicate pathology. 4. Mesentery: The mesentery, which suspends the small bowel, is visible as thin lines radiating from a central point (the root of the mesentery). It contains blood vessels and lymph nodes. 5. Valvulae Coniventes: These folds, visible as thin, linear or curvilinear structures projecting into the lumen, are best seen when the small bowel is distended with fluid. They are more prominent in the jejunum than the ileum. 6. Peristalsis: On dynamic CT, peristaltic waves may be observed as subtle movements of the bowel loops.