Expansion of various types of ileal reservoirs in situ. An experimental study in rats.

In experiments on rats four types of ileal reservoirs were constructed and left to expand in situ. After 3 months the volumes and tissue weights of the various reservoirs were compared. The reservoir types were: two loops, isoperistaltic (type I), two loops, antiperistaltic (type II), three loops, S-shaped (type III) and "four loops', double-folded U loop (Kock pouch) (type IV). There was a considerable volume increase in all types of reservoir as well as a marked increase in their tissue weight. The expansion of the reservoirs in groups III and IV was significantly greater than that in groups I and II. The difference in expansion could possibly be explained by the greater radius in three- and four-loop reservoirs compared with two-loop reservoirs if Laplace's law is applied to this process. According to this law the tension in the wall of a tube increases with increasing radius.