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.
Every child with day and night wetting is a suspect for vesicourethral dysfunction on a behavioral basis, which, when severe, appears as a syndrome that we have called the nonneurogenic neurogenic bladder. Futile attempts by the child at sphincteric urinary control in the face of uncontrollable bladder contractions not only produce the symptoms but also the anatomical and functional changes: vesical trabeculation, distortion of the ureterovesical orifices and dilatation of the upper tracts, along with residual urine and consequent bacteriuria. These changes are indistinguishable from obstructive or, particularly, neurogenic factors, although these causes must be ruled out. Urodynamic investigations in these children show incoordination between detrusor contraction and the expected but not forthcoming urethral sphincteric relaxation. Since these children usually are toilet trained initially, the incoordination appears to be a learned behavior or habit, perhaps as a response to under-appreciated detrusor contractions. Reversal of the syndrome is achieved by suitable medication and by some form of suggestion or retraining. Reparative operations will fail if done before the system is balanced.
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