Fig. 16.6 Transit time in normal persons and in many patients with mild or moderate tropical sprue is quite variable; it is usually 1 hour or slightly less, but may extend to 3 or 4 hours. In this patient with mild tropical sprue, the small bowel mucosal pattern is essentially normal and the transit time is uncommonly rapid, with barium passing through the entire small intestine and reaching the cecum in 15 minutes.

Transit Time. There are no universally accepted criteria for normal transit time so that, per se, it contributes little or nothing to a definitive diagnosis. However, the following comments are offered. Transit time may be defined as the time elapsed between ingestion of the barium meal and the appearance of barium in the colon. In the normal person and in many patients with sprue, the transit time is most frequently 1 hour or less (Fig. 16.6), but it may extend to 3 or 4 hours. The column is usually unbroken, but occasionally there is delay in complete emptying of the stomach, so that upper segments of bowel may be revisualized. Only the most severe cases of sprue show significant delay or segmentation. ( Fig. 16.12.)

Although the normal propulsion wave is usually interrupted in sprue, some barium may reach the colon in normal time. Sheehy and Floch have pointed out that propulsion of the succus entericus is due not only to the action of the tunica muscularis (circular and longitudinal muscles) but also to the action of the muscularis mucosa and the muscles of the villi and the cilia-like action of the microvilli. They believed the latter may in fact contribute more to motility than the gross movements of the tunica muscularis. It is known that the muscularis mucosa reacts to local stimuli (food, pressure, chemicals). The finding in sprue that some barium reaches the large bowel promptly without the aid of normal peristalsis then becomes explainable.