Mathematical prediction of ileal pouch capacity.

Restorative proctocolectomy is an operation still in the stage of development. Three main types of ileal pouch construction are used, but the advocacy of each probably arises more from familiarity and convenience than from scientific considerations. Since, other things being equal, pouch capacity can be expected to affect stool frequency, it seemed reasonable to examine calculable pouch capacity geometrically for different methods of construction. A mathematical model was therefore used to compare the double loop ('J') type with the quadruple loop ('W') construction. The W was estimated to have a capacity more than half as great again as the J. Similarly anastomotic methods which encroach on the ileal circumference by creating an inverted edge can be expected to reduce resultant capacity by 10 per cent or more.