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- In this
issue a discussion of the following article concerning Artificial
Anal Sphincter will take place:
Multicenter retrospective analysis of the outcome of artificial
anal sphincter implantation for severe fecal incontinence.
Authors: Altomare DF, Dodi G, La Torre F, Romano G, Melega
Journal: BJS 2001; 88(11):1481-6.
flow equation point of view the artificial anal sphincter
works by maintaining adequate A.C. Length dictated by the
diameter of the cuff diameter and minimizes the A.C. diameter
by the inflation of the balloon.
The presence of a pliable anal canal is essential for the
action of the Artificial Anal Sphincter in order to reduce
the A.C. diameter. The procedure should be accompanied by
lysis of any fibrosis, which may cause tethering of the A.C.
to the peri-anal structures.
The Artificial sphincter tries to mimic the normal anal sphincter
by its ability to relax in order to achieve normal unobstructed
defecation on volition, using artificial inflatable anal sphincter
replacement was followed by Anismus if the cuff diameter used
is 2.9 cm as compared to cuff diameter of 2 cm in this study
from Italy. This finding can be explained by the flow equation
simply by the fact that the cuff diameter represents the minimal
A.C. length which can be achieved during defecation. For example
at any given anal canal diameter (e.g. 2 cm), using 2.9 cm
cuff would lead to a 45% increase in A.C. resistance during
defecation which needs a proportionate increase in IRP during
defecation in order to maintain the same Flow Index achieved
with 2 cm diameter cuff during defecation (more straining
for the increasing resistance).
The use of cuffs with 2.9 cm diameter should be abandoned
and the inner diameter of the Artificial sphincters with 2c
diameter cuffs should be tailored according to the mean intrarectal
pressures during defecation measured preoperatively and accordingly
the expected flow index postoperatively.
(N.B. for the details of such calculations, please contact
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