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16
1 History of the Treatment of Anorectal Malformations
47. Lynn HB (1961) Anal atresia: results of surgical treatment. Sec of Pediatr Surg, Mayo Clinic Rochester,
Minn 1961
48. Partridge JP, Gough MH (1961) Congenital abnormalities of the anus and rectum. Br J Surg 49:37–50
49. Trusler GA, Wilkinson RH (1962) Imperforate anus: a
review of 147 cases. Can J Surg 5:269–277
50. Cozzi F, Wilkinson AW (1968) Congenital abnormalities of anus and rectum: mortality and function. Br
Med J 1(5585):144–147
51. Soave F (1969) Surgery of rectal anomalies with
presentation of the relationship between the colonic
muscular sleeve and the puborectalis muscle. J Pediatr
Surg 4(6):705–712
52. Louw JH, Cywes S, Cremin BJ (1971) The management of anorectal agenesis. S Afr J Surg 9(1):21–30
53. Boe J, Knutrud O, Sommerchild HC (1974) Anal atresia. Zeitschrift for Kinderchir 14:171–177
54. Nixon HH, Puri P (1977) The results of treatment of
anorectal anomalies: a thirteen to twenty year follow up. J Pediatr Surg 12(1):27–37
55. Smith EI, Tunell WP, Williams GR (1978) A clinical evaluation of the surgical treatment of anorectal malformations (imperforate anus). Ann Surg
187(6):583–592
56. Holschneider AM (1983) Treatment and functional
results of anorectal continence in children with imperforate anus. Acta Chir Belg 82(3):191–204
57. Varma KK (1991) Long-term continence after surgery
for anorectal malformations. Pediatr Surg Int 6:32–35
58. Chatterjee SK, Talukder BC (1969) Double termination of the alimentary tract in female infants. J Pediatr
Surg 4(2):237–243
59. Rintala RJ (1996) Anorectal malformationmanagement and outcome. Semin Neonatol 1:219–230
60. Endo M, Hayashi A, Ishihara M, Maie M, Nagasaki
A, Nishi T, Saeki M (1999) Analysis of 1,992 patients
with anorectal malformations over the past two
decades in Japan. Steering Committee of Japanese
Study Group of Anorectal Anomalies. J Pediatr Surg
34(3):435–441
61. Schärli AF (1986) History of Colostomy in childhood. Prog Pediatr Surg 20:188–198
62. Ito Y, Yokoyama J, Hayashi A, Ihara N, Katsumata
K (1981) Reappraisal of endorectal pull-through procedure. I. Anorectal malformations. J Pediatr Surg
16(4):476–483
63. Brayton D, Norris WJ (1958) Further experiences
with the treatment of imperforate anus. Surg Gynecol
Obstet 107(6):719–726
64. Aluwihare AP (1989) Imperforate anus in male children: a new operation of primary perineal rectourethroanoplasty. Ann R Coll Surg Engl 71(1):14–19
65. Banu T, Hannan MJ, Aziz MA, Hoque M, Laila K
(2006) Rectovestibular fi stula with vaginal malformations. Pediatr Surg Int 22(3):263–266
66. Santulli TV, Kiesewetter WB, Bill AH Jr (1970)
Anorectal anomalies: a suggested international classifi cation. J Pediatr Surg 5(3):281–287
67. Santulli TV, Schullinger JN, Kiesewetter WB, Bill
AH Jr (1971) Imperforate anus: a survey from the
members of the Surgical Secton of the American
Academy of Pediatrics. J Pediatr Surg 6(4):484–487
68. DeVries PA, Peña A (1982) Posterior sagittal anorectoplasty. J Pediatr Surg 17(5):638–643
69. Peña A, DeVries PA (1982) Posterior sagittal anorectoplasty: important technical considerations and new
applications. J Pediatr Surg 17(6):796–811
70. Stephens D, Smith D (1988) Anorectal malformations
in children: update 1988. Birth Defects Orig Artic Ser
24(4):1–604
71. Holschneider AM, Hutson JM (2006) Anorectal malformations in children. Embryology, diagnosis, surgical treatment, follow-up. Springer, Berlin, Heidelberg,
New York, p 10
72. Willital GH (1998) Endosurgical intrapuborectal
reconstruction of high anorectal anomalies. Pediatr
Endosurg Innovative Tech 2(1):5–11
73. Georgeson KE, Inge TH, Albanese CT (2000)
Laparoscopically assisted anorectal pull-through for
high imperforate anus–a new technique. J Pediatr
Surg 35(6):927–930; discussion 930–931
74. Peña A, Bonilla E, Mendez M, Sanchez L (1992) The
posterior sagittal approach – further pediatric applications. Pediatr Surg Int 7(4):274–278
75. Peña A, Filmer B, Bonilla E, Mendez M, Stolar C
(1992) Trans-anorectal approach for the treatment of
urogenital sinus: preliminary report. J Pediatr Surg
27(6):681–685
76. Siegel JF, Brock WA, Peña A (1995) Transrectal posterior sagittal approach to prostatic utricle (Müllerian
Duct Cyst). J Urol 153(3):785–787
77. Peña A, Hong AR (2003) The posterior sagittal
trans- sphincteric and trans-rectal approaches. Tech
Coloproctol 7:35–44
78. Peña A, Levitt M (2002) Colonic inertia disorders in
pediatrics. Curr Probl Surg 39(7):661–730
79. Peña A (1997) Total urogenital mobilizationan easier way to repair cloacas. J Pediatr Surg
32(2):263–268
80. Peña A, Kessler O (1998) Posterior cloaca: a unique
defect. J Pediatr Surg 33:407–412
81. Peña A (1996) Bowel management after surgery for
imperforate anus. Dialogues Pediatr Urol 19(12):1–8
82. Peña A, Guardino K, Tovilla JM, Levitt MA,
Rodriguez G, Torres R (1998) Bowel management for
fecal incontinence in patients with anorectal malformations. J Pediatr Surg 33(1):133–137
83. Bischoff A, Levitt MA, Bauer C, Jackson L, Holder
M, Peña A (2009) Treatment of fecal incontinence
with a comprehensive bowel management program. J
Pediatr Surg 6(44):1278–1284
84. Bischoff A, Levitt MA, Peña A (2009) Bowel management for the treatment of pediatric fecal incontinence. Pediatr Surg Int 25(12):1027–1042
Basic Anatomy and Physiology of Bowel Control
2
The reader may be surprised for not fi nding in
this chapter many of the traditional terms historically used to refer to the different portions of the
sphincter mechanism of the human being. We use
a different terminology that we believe is realistic, useful, and with important practical and technical implications for the practicing surgeon.
This is a result of our observations of the different anatomic variants, found in more than 2,032
surgical explorations of the pelvis and the anorectum of patients suffering from anorectal malformations, as well as many others operated to
resect tumors and to repair pelvic organs (urethra, vagina, and rectum).
In the early times, when we performed the fi rst
posterior sagittal approaches to repair anorectal
malformations, infl uenced by the traditional concepts expressed in the available textbooks on the
subject [
talis sling,” the “pubococcygeal muscle,” the
“pubourethralis muscle,” the “iliococcygeal muscle,” the “superfi cial portion of the external
sphincter,” the “deep portion of the external
sphincter,” and the “internal sphincter,” and we
were rather frustrated for not seeing what was
described in the textbooks. Or at least, what we
were seeing was very different to what was
described.
Electronic supplementary material Supplementary
material is available in the online version of this chapter at
10.1007/978-3-319-14989-9_2 .
1 , 2 ], we were looking for the “puborec-
In addition, through the years we found that
what we observed as part of the sphincter mechanism in one patient was never the same as the one
that we saw in another one. After a large experience with the surgical treatment of anorectal malformations, we are now certain to believe that we
are dealing with a spectrum of anatomic
variations.
We are aware of the fact that human beings
(and surgeons are not exceptions) prefer to deal
with artifi cial, man-made, classifi cations to refer
and to discuss biological phenomenon. Yet, we
like to say that Mother Nature does not like our
classifi cations and continues producing humans,
animals, and biological specimens following a
spectrum type of pattern. We recognize that it is
not easy from the clinical point of view to talk
about spectrums, but we could not ignore reality.
Figure 2.1 shows what we think is the best
photograph ever taken of the pelvic anatomy of a
male cadaver. The authors managed to show a
perfect sagittal section. We feel admiration and
respect for such achievement. This magnifi cent
photograph was reproduced with permission
from the excellent “Colon Atlas of Human
Anatomy” by R.M.H. McMinn Emeritus
Professor of Anatomy, Royal College of
Surgeons of England and University of London
and R.T. Hutchings, photographer, formerly
Chief Medical Laboratory Scientifi c Offi cer,
Royal College of Surgeons of England. Year
Book Medical Publishers, Inc., Chicago 1977,
page 248.
A. Peña, A. Bischoff, Surgical Treatment of Colorectal Problems in Children,
DOI 10.1007/978-3-319-14989-9_2, © Springer International Publishing Switzerland 2015
17
18
2 Basic Anatomy and Physiology of Bowel Control
Fig. 2.1 Photograph of a sagittal section of a human
cadaver. 1 Rectus abdominis; 2 Extraperitoneal fat;
3 Sigmoid colon; 4 Promontory of sacrum; 5 Rectum;
6 Coccyx; 7 Anococcygeal body; 8 External anal sphinc-
ter; 9 Anal canal with anal columns of mucous membrane;
10 Perineal body; 11 Ductus deferens; 12 Epididymis;
13 Testicle; 14 Spongy part of urethra and corpus
spongiosum; 15 Corpus cavernosum; 16 Bulbospongiosus;
17 Perineal membrane; 18 Sphincter urethrae;
19 Membranous part of urethra; 20 Pubic symphysis;
21 Prostate gland; 22 Prostatic part of urethra; 23 Seminal
colliculus; 24 Bristle in ejaculatory duct; 25 Internal ure-
thral orifi ce; 26 Bladder; 27 Bristle passing up into right
ureteral orifi ce; 28 Rectovesical pouch
Figure 2.2 shows an MR image of the sagittal
section of the pelvis of a normal child. It is really
remarkable what modern imaging technology has
achieved. We invite the readers to look in a very
detailed way these two pictures (Figs. 2.1 and
2.2 ). The same muscle structures shown in the
cadaver are present in the MRI picture. A nonbiased, objective view of these two fi gures does
not allow us to identify separately the puborectalis, ischiococcygeal, pubourethralis, and iliococcygeal muscles and deep external sphincter,
superfi cial external sphincter, and internal
sphincter.
Rather, one can see a muscle structure that
comes from the anterior aspect of the lowest
part of the sacrum and coccyx and runs all the
way down to the skin attached to the posterior
rectal wall. It actually runs in continuum and
one cannot see any hint of separation of different structures. In our observations of normal
human beings (not only in cases of anorectal
malformations) operated posterior sagittally for
other reasons (tumors, trauma), and using an
electrical stimulator, we have always been able
to identify this strong funnel-like muscle structure. If one touches that muscle structure in the
upper portion, one can elicit a contraction that
pushes the rectum forward as described for the
levator muscle. If one touches the lowest part of
that muscle, one can see an elevation of the
anus, and perhaps that is why originally this
structure was called levator muscle. That portion of this sphincter mechanism made mainly
of vertical fi bers running parallel to the rectum
we call it “muscle complex,” to differentiate it
from the upper portion (levator) that is made out
of horizontal fi bers that compress the rectum
from behind. However, these different portions
of the sphincter mechanism do not contract separately; in real life, they contract in a massive
unifi ed way (Animations 2.1 , 2.2 , 2.3 , 2.4 , and
2.5 ). The muscle fi bers running longitudinally
(parallel to the rectum) elevate the anus when
they contract, whereas those fi bers that surround
the rectum are the ones that produce the compression of the rectum posteriorly. Perhaps the
point of maximal contraction of this funnel-like
muscle structure is what has been considered
the puborectalis sling, but we must emphasize
that there is no real anatomic separation of these
structures. Near the skin, the funnel- like muscle
joins other types of muscle that run superfi cial
under the skin and divide into two portions, one
on each side of the anus, and that is why we call
those “parasagittal fi bers.” The contraction of
these muscles may produce the impression of
closing the anus in a circular fashion; yet, actually these are parasagittal fi bers that join one
side with the other, posterior and anterior to the
anal opening. The parasagittal fi bers run actually perpendicular to the muscle complex. We
arbitrarily use the term “levator” to refer to the
upper portion of the funnel-like muscle mecha-
2 Basic Anatomy and Physiology of Bowel Control
a b
19
Fig. 2.2 MRI of a sagittal section of the normal pelvis. ( a ) Relaxed sphincter mechanism. ( b ) Contracted sphincter
mechanism
nism and use the term “muscle complex” to its
lower portion. The point where the muscle complex and parasagittal fi bers cross represents the
limits of the sphincter.
When the anatomy of the anorectal sphincters
is presented in this rather simplistic way, it is
easy to teach and to learn.
Traditional anatomy concepts have been
repeated from one generation to another, full of
details or concepts without clinical relevance.
The medical students are frequently obligated to
learn some of those concepts.
We have been impressed by publications
related with the anatomy of the sphincters; the
authors frequently show real photographs of the
anatomy, yet they over-impose arrows to show
inexistent, imaginary structures [
2 – 5 ]. In other
words, photographs show the real anatomy,
whereas the diagrams or the arrows show what
the authors wanted to see.
More recently, advances in the technology of
imaging show images (Fig. 2.2 ) of the real anat-
omy; however, again the authors fabricate other-
wise unnecessary diagrams showing their
preconceptions and biases [
6 – 13 ].
It is even more impressive to see how rather
bizarre anatomic concepts, like the idea of a “triple loop” without any evidence to support its
existence, are accepted, published, and repeated
between surgeons [ 14 , 15 ].
In a medical community where everybody
seem to be able to see clearly structures such as
the puborectalis muscle and all the other portions
of the sphincter mechanism, very few dare to
express skepticism and disagree [
16 , 17 ]. During
our literature review, we found an excellent honest paper written by Dr. Arthur F. Dalley II, PhD,
[ 17 ]. After a very thoughtful discussion, he con-
cludes saying: “I recommend that the three-part
external anal sphincter be removed from gross
anatomy texts, dissectors and atlases and be relegated to the junkyard of anatomic trivia where it
may languish for the sake of the historical anatomist or the rare individual who spends time carving out the most meticulous of dissections.” This
is a paper that all colorectal surgeons must read.
20
2 Basic Anatomy and Physiology of Bowel Control
2.1 Internal Sphincter
This elusive structure has been described as a
thickening of the circular layer of smooth muscle
of the bowel in the area of the anorectum. The
literature related to this structure, in general, has
the following characteristics:
• There are no good quality photographs showing the sphincter.
• There is no precise description of its size and
limits at different ages.
• Most papers discuss the “internal sphincter”
based on manometric fi ndings.
• Some authors believe that the “internal sphincter” is very important for bowel control [ 18 , 19 ].
• Others believe that its contribution for bowel
control is not signifi cant [ 20 ].
• Many authors believe that the lack of relaxation of this structure is responsible for many
patients suffering from constipation and
megarectosigmoid (see Chap. 25 ).
• Our direct observations of the entire posterior anorectal wall in normal individuals did
not allow us to see the thickening of the
smooth muscle that presents the “internal
sphincter.”
• As a consequence of all the importance that
many doctors gave to the “internal sphincter,”
pediatric surgeons have been debating about
the possible existence of an “internal sphincter” in cases of anorectal malformations,
located at the most distal part of the bowel, the
portion attached to the urogenital tract (fi stula). Some surgeons believe that it is very
important to preserve the most distal portion
of the bowel in order to guarantee bowel control [
21 – 23 ], whereas others believe that it
must be resected to avoid constipation [ 24 ].
Our results in terms of bowel control show
that fecal continence and constipation are
unrelated to the preservation or resection of
that portion of the bowel (see Chap. 15 ).
All these descriptions of our literature fi nd-
ings related with the “internal sphincter,” plus our
concepts discussed in Chap. 25 , explain our skep-
ticism related with the existence, function, and
relevance of this structure.
2.2 General Anatomic Principles in Anorectal Malformations
Figures 2.3 , 2.4 , 2.5 , and 2.6 show the anatomic
variations that form part of the spectrum seen in
cases of anorectal malformations. Animation 2.1
shows the sagittal view of the anatomy of the pel-
Fig. 2.3 Diagram showing the most common anatomic
sphincter pattern seen in patients with perineal fi stula
Fig. 2.4 Diagram showing the most common anatomic
sphincter pattern seen in patients with bulbar fi stula
2.2 General Anatomic Principles in Anorectal Malformations
21
Fig. 2.5 Diagram showing the most common anatomic
sphincter pattern seen in patients with prostatic fi stula
Fig. 2.6 Diagram showing the most common anatomic
sphincter pattern seen in patients with bladder neck
fi stula
vis of a normal human being. Figure 2.3 shows
the most benign of all defects which is the perineal fi stula. The sphincter mechanism in these
types of cases is almost normal. The rectum, on
the other hand, deviates in its lowest portion to
open in the perineal body, anterior to the center of
the sphincter. The rectum is dilated.
Figure 2.4 shows the anatomy of a patient
born with a rectourethral bulbar fi stula. Most of
these patients have a sphincter mechanism reasonably good, perhaps not as strong and good as
the sphincter of a normal person or a patient with
a perineal fi stula. The rectum connects to the
lowest portion of the posterior urethra which we
call bulbar urethra.
Figure 2.5 shows the anatomy on a patient
with a rectoprostatic fi stula. One can see that the
sphincter mechanism is much more primitive and
weak. In addition, the distance between the
sacrum and the pubis is signifi cantly shorter. The
available space for a pull-through is getting
smaller, the sphincter mechanism weaker, and
obviously the prognosis is not as good as in the
previous defects.
Figure 2.6 shows the anatomy of a patient
with a recto-bladder neck fi stula. The rectum
opens at the bladder neck, the sphincter mechanism is very tenuous, sometimes almost nonexistent, and the distance between the sacrum and the
pubis is very short. Sometimes it makes it almost
impossible to pull the rectum down. As one can
see in this series of diagrams, in the case of the
rectourethral bulbar fi stula, once we separate the
rectum from the urethra, it is conceivable that
the rectum can be placed within the limits of the
sphincter with minimal mobilization and will be
completely covered by the sphincter mechanism.
Whereas in Fig.
2.5 , sometimes we fi nd a rectum
that does not fi t into the tenuous, delicate sphincter mechanism, and one has the feeling that the
reconstruction was not ideal. And fi nally, in some
of the recto-bladder neck fi stulas, it becomes
very obvious that the sphincter is very weak and
that the patient most likely will have fecal incontinence. In fact, as we will discuss in our results,
patients with recto-perineal fi stulas have a 100 %
chance of bowel control provided they have a
good operation. Patients with bulbar fi stula have
85 % chances, prostatic fi stula 60 % chances, and
bladder neck fi stula only 20 % chances. Similarly,
characteristically, the sacrum usually is more and
more primitive, as we go into higher and higher
22
2 Basic Anatomy and Physiology of Bowel Control
locations of the rectum, as well as the
characteristics of the sphincter and the space
available between the sacrum and pubis. The
chance of suffering from tethered cord also
increases in higher malformations. The exception
is represented by some patients with perineal fi stulas. This particular group of patients has more
tendencies to suffer from presacral masses and
tethered cord. The anatomic differences shown in
Figs. 2.3 , 2.4 , 2.5 , and 2.6 and Animations 2.2 ,
2.3 , 2.4 , 2.5 , and 2.6 are seen in real life. However,
as it is well known by all surgeons, in medicine
and surgery, there are no “nevers” and there are
no “always.” In other words, it is possible to see,
although very unusual, a perineal fi stula with
very poor sphincter mechanism and also to see a
recto-bladder neck fi stula with a rather goodlooking sphincter mechanism, but those are
exceptions. Most of the time, as the rectum is
located higher connecting to the urogenital tract,
the sacrum tends to be shorter, the distance
between the sacrum and pubis decreases, and the
characteristics of the sphincter become more and
more rudimentary and weak.
2.3 Nerves
We surgeons frequently refer to the “lack of
nerves” when we deal with patients with anorectal malformations with bad functional prognoses.
Yet, we actually never see the nerves when operating on these patients. There are no precise scientifi c studies that give evidence of the presence
or absence, as well as characteristics and precise
location, of the pelvic nerves in cases of anorectal
malformations. We work, always assuming, that
the higher the location of the rectum and its connection to the urogenital tract, as well as the more
defi cient sacrum is, the more defi cient the nerves
are. In addition, the fact that we have to mobilize
the rectum from higher distances most likely
means that we have to sacrifi ce more nerves. We
also assume that in a patient with absent sacrum,
all the nerves that normally come out of the segments of the sacrum and innervate the pelvic
organs are absent, or defi cient, and that may
explain why patients with absent sacrum have
zero possibility of having bowel and urinary control. Patients with anorectal malformations are
represented by a spectrum in terms of sacrum
defi ciency that goes from patients with normal
sacrum to patients with completely absent
sacrum.
We know that under normal circumstances,
the nerves that innervate the bladder neck urinary
tract and corpora come from the orifi ces of the
sacrum and run lateral to the rectum in order to
reach the corpora, the bladder neck, and the rectum itself. Therefore, from the early times, Dr.
Douglas Stephens [ 25 ] recommended (and is still
valid) to try to remain exactly in the midline as
much as possible during our surgical explorations. Once the surgeon reaches the rectum, all
the dissection of the rectum must be performed,
staying as close as possible to the rectal wall to
avoid the damage of nerves that supposedly run
lateral to the rectum. In other words, the further
away from the rectum, the more chances to injure
nerves.
Concerning the anatomy of the pelvic autonomic nerves, the reader is referred to anatomy
books and an excellent paper [ 26 ]. From the read-
ing of that material, we reinforce our belief that it
is essential to remain in the midline while
approaching the pelvis and to dissect the rectum
remaining as close as possible to the bowel wall,
in order to minimize the possibilities to injure
autonomic nerves and avoid neurogenic bladder
and impotence.
We have evidence from patients that had previous failed attempted repairs and that were born
with a “good” malformation and yet they suffered from fecal and sometimes urinary incontinence. Reading the operative reports of those
patients, one fi nds that the surgeon actually got
lost and certainly went out of the midline, which
may explain the nerve damage.
2.4 Blood Supply
Unfortunately, there are no scientifi c detailed
anatomic studies of the blood supply of the pelvic
organs of patients with anorectal malformations.
Again, what we have learned from our surgical
2.5 Basic Physiology Principles of Bowel Control
23
explorations is that it seems like the rectum has
an excellent intramural blood supply, as evidenced by the fact that in every case of anorectal
malformation that we operate on, we separate the
rectum from the urogenital tract, and then we
have to mobilize the rectum enough to reach the
perineum. In order to do that, we performed a circumferential dissection, dividing all the extrinsic
vessels and bands that hold the rectum up in the
pelvis. In other words, we are basically devascularizing the rectum. We sacrifi ce its entire extrinsic blood supply. Yet, provided the wall of the
rectum remains intact and the inferior mesenteric
vessels are preserved, the intramural blood supply of the proximal part provides enough to
maintain alive the distal part of the rectum. This
fi nding should not be extrapolated to other parts
of the colon. The blood supply of the colon in
patients with anorectal malformations is basically the same as in normal individuals, except in
patients with cloacal exstrophies and patients
with a malformation called “rectal pouch” in
which the entire colon is represented by a single
saccular piece of colon with a very abnormal
bizarre type of blood supply (picture).
2.5 Basic Physiology Principles
of Bowel Control
We take care of many babies born with severe
anatomic defi ciencies; we can certainly repair
their anatomy, but we cannot restore their normal
function; however, we try to help them to have a
normal social life, with the implementation of
our “bowel management program.” Unfortunately,
there is another large group of patients who suffer
from fecal incontinence as a consequence of a
technically defi cient operation. That is obviously
something highly regrettable, but most important
is the fact that it is preventable. For that, it is
imperative for the surgeon to know a few basic
but extremely important anatomic and physiologic principles.
In order to have bowel control, it is necessary
to have three very important elements:
A. Sensation
B. Sphincter
C. Rectosigmoid motility and reservoir function
A . Sensation – this is the fi rst indispensable ele-
ment for bowel control. The anal canal is perhaps the most sensitive part of the human
body. There, we are capable of discriminating
gas, from liquid and from solid fecal matter
[ 27 ]. The anal canal remains collapsed by the
effect of the muscle tone of the sphincter
mechanism that surrounds it. When the fecal
matter (liquid, solid, or gas) reaches the anal
canal due to active rectal peristalsis, we perceive it and, depending on the surrounding
circumstances, decide to use our voluntary
sphincter mechanism, to occlude the lumen
of the anal canal and avoid a bowel movement, until the circumstances are appropriate
to have a bowel movement.
Above the anal canal, in the rectum, we do
not have the exquisite sensation described for
the anal canal. However, a distention of the
rectum with a balloon causes a vague sensation of fullness that is known as proprioception [ 28 ].
The implications of these facts for us surgeons are obvious. We must try to preserve
intact the anal canal during our operations in
patients with normal anal canal, such as
patients suffering from Hirschsprung’s disease, severe constipation, infl ammatory
bowel disease, and familial polyposis.
The overwhelming majority of patients
with anorectal malformations are born without an anal canal, except for a rare malformation called rectal atresia. Patients with
perineal fi stula have a rather primitive anal
canal. This means that patients with anorectal
malformations, under the best circumstances,
do not have “perfect” bowel control. Many
patients born with a malformation with good
functional prognosis behave like normal children, yet when they have a severe episode of
diarrhea, it becomes evident that they are less
than perfect in terms of bowel control.
B . Sphincter – the voluntary sphincter mecha-
nism maintains a certain tone constantly.
However, there is a common misconception
consisting on believing that a sudden relaxation of the sphincter will produce escape of
24
2 Basic Anatomy and Physiology of Bowel Control
feces. That is simply not true. In fact, a human
being can only have a bowel movement when
the rectosigmoid has a peristaltic wave that
pushes the stool out. Human beings actually
use the voluntary sphincter occasionally, to
prevent the passing of gas or fecal matter in
inadequate circumstances.
C . Rectosigmoid motility and reservoir func-
tion – after many years of working with
patients suffering from bowel control problems, we came to realize that rectosigmoid
motility and its reservoir function are the
most important element for bowel control.
The rectosigmoid remains relaxed most of the
time, acting as a reservoir of fecal matter.
That is an extremely important function,
since it allows human beings to have a social
life and only use the toilet every 24–48 h.
The implications of this, for us surgeons, are
also very obvious. The removal of the rectosigmoid and connection of a more proximal portion
of the colon, to the anal canal, means elimination
of the reservoir function which results in an
almost constant attempt of the colon to empty. If
the anal canal is maintained intact, the resection
of the rectosigmoid will result in many bowel
movements during the day and a constant effort
to avoid them. We all have seen how a colostomy
works. It passes stool almost constantly. An
ascending colostomy will be passing more often
liquid stool, and as we move distally, the stool
becomes more solid and the peristalsis less active.
That means that connecting a piece of colon
directly to the anal canal (without reservoir) will
produce very frequent bowel movements, and it
will require a well-preserved anal canal to maintain continence.
We can easily imagine what happens when we
remove the natural reservoir (rectosigmoid) and
damage or resect the anal canal. The result will
be permanent fecal incontinence.
Another scenario is the case of an absent anal
canal and sphincter; we have seen that in cases of
trauma. The motility of the rectosigmoid and its
reservoir function is preserved, and therefore, it
is possible that a particular patient behaves like if
he/she was fecally continent, provided he/she
does not have episodes of diarrhea or multiple,
irregular, unpredictable bowel movements.
Using our imagination, we conceive the possibility of manipulating the rectosigmoid motility, using pharmacologic agents, in order to
paralyze the rectosigmoid when required and to
provoke a peristaltic wave to empty the rectosigmoid when the surrounding circumstances are
appropriate. In fact, we consider that kind of
treatment more likely to be successful rather than
trying to reconstruct the sphincters or use artifi cial sphincters, without taking into consideration
the two more important elements that are sensation and motility.
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