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Defecation Norm Gram
Continence Norm Gram
Applications of the Theory
Facts and Controversies
continence is maintained by the Integrated effect of 4 Primary
mechanical factors namely Intrarectal pressure, Dynamic viscosity
of rectal contents and Anal canal Length and Diameter. The relative
role played by each factor can be quantitated by its share in
the flow equation.
The dynamic viscosity (D.V.) of soft well formed stools is 68.9
times that of air , while D.V. of watery stools is 38 times
that of air , which explains why anal canal resistance to air
is much lower than that to water, which is 1.8 times lower than
that for soft well formed stools.
The controversy concerning the Anorectal angle (ARA): The
ARA does not show itself in the flow equation and can be absent
in the presence of adequate anal canal length and diameter maintaining
adequate anal canal resistance. However owing to the visico-elastic
properties of the anal canal pulling the anorectal junction
upwards and forwards increases the anal canal length and decreases
anal canal diameter and hence indirectly increases anal canal
resistance to flow.
The absence of correlation between the presence of anal sphincter
injuries as detected by U.S. or MRI and anal incontinence is
explained by the fact that the injury should decrease anal canal
length and increase anal canal diameter to a certain degree
which would decrease the anal canal resistance enough to cause
clinical and mathematic Anal Incontinence.