Anatomically, the small intestine is a convoluted tube which begins in the upper part of the abdomen just distal to the pylorus and ends at the ileocecal valve. Roentgenologically, it is a highly active and dynamic organ with certain characteristic anatomic and physiologic features. Normal roentgen morphology is, for the most part, dependent on muscular tone, physiologic motion, mucosal pattern or a combination of these three factors.
The length of the small intestine is variable. At autopsy it may measure from 5 to 7 meters. Intubation by measured length of tubing has indicated a length of from 2.5 to 3 meters from the pylorus to the cecum. Such figures, however, may not be accurate because the intestine may telescope itself along the course of the tube and thus produce abnormal shortening. It is generally assumed that the upper three fifths of the mesenteric small intestine is jejunum and the lower