Selection of intestinal segments for bladder substitution: physical and physiological characteristics.

Detubularized bowel segments provide greater capacity at lower pressure and require a shorter length of intestine than do intact segments. Four factors account for their superiority: 1) their configuration takes advantage of the geometric fact that volume increases by the square of the radius so that a patch or pouch has a larger diameter than a tube, 2) they accommodate to filling more readily because, as LaPlace's law states, the container with the greater radius and, thus, the greater mural tension will hold larger volumes at lower pressure, 3) compliance is superior to that of the tubular bowel and 4) contractile ability is blunted by the failure of contractions to encompass the entire circumference. For these reasons detubularized segments store more urine at lower pressures.