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Unusual duodeno-pancreatic relationships associated with incomplete rotation of mid-gut loop.

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Unusual Duodeno-pancreatic Relationships
Associated with Incomplete Rotation
of Mid-gut Loop
PAULA M. WILSON
Department o f Anatomy, University of Cape T o w n , Medical School,
Observatory, Cape T o w n , Republic of South Africa
ABSTRACT
A 79 year-old European female cadaver presented the usual features
of second stage arrested mid-gut rotation accompanied by unusual mesenteric attachments and pancreatico-duodenal relationships.
The mesentery, whose root extended from the lower pole of the Tight kidney
diagonally across the posterior abdominal wall to end just medial to the left sacroiliac joint, enclosed most of the small bowel and the proximal large bowel. The unusually short duodenum began 2.5 cm to the left of the mid-line and described a 13
cm U loop with an upward concavity in which rested the pancreas; this loop and the
related pancreas were enclosed in a persistent, transversely placed mesoduodenum.
The common bile duct crossed the anterior surface of the pancreas to open a t the
greater duodenal papilla 2.5 cm from the pylorus. The main pancreatic duct lay
much closer to the anterior than to the posterior aspect of the gland. The lesser duodenal papilla was situated on the posterior wall of the duodenum. The hepatic artery
arose in common with the superior mesenteric artery and encircled the pancreas. The
pancreatico-duodenal vessels were predominantly distributed upon the posterior aspect
of the pancreas and duodenum.
It appears that in this specimen the anterior and posterior aspects of the duodenum are transposed, the reversal of surfaces also involving the pancreas. Causative
factors are discussed with reference to the literature.
Arrested rotation of the mid-gut loop at
the second stage (Dott, '23) (sometimes,
but less accurately, termed non-rotation)
produces a characteristically modified disposition of the intestine; the coils of small
intestine occupy the right and central regions of the abdomen while the colon is
compressed int,o the left half of the abdominal cavity. This anomaly can be
present without impairing the functioning
of the intestinal tract, so that the condition is compatible with prolonged life and
may remain unrecognized throughout life.
Although its incidence can only be a fracti,on of 1%, examples are found from time
to time in dissecting-room cadavers and
over the years a considerable number have
been described in greater or lesser detail.
A white female cadaver aged 79 years
presenting this condition, dissected in our
laboratories during '63, showed among
other unusual features an arrangement of
the duodenum and pancreas differing considerably from those described in any previous reports available to us. These findings and their interpretation form the subject of the present study.
ANAT. REC., 149: 397-404.
General features
The usual features of second stage nonrotation of the mid-gut loop were present,
small bowel occupying the right half of the
abd,ominal cavity and large bowel the left
half (see fig. 1 ) ; the caecum rested on the
pelvic brim just to the left of the midline
and the terminal ileum joined it from the
right. The mesentery began at the lower
pole of the right kidney and, extending for
20 cm from the right upper to the left lower
quadrant of the abdomen, skirted the brim
of the pelvis and ended near the left sacroiliac joint. Enclosed in the margin of the
mesentery were ooils of small intestine, the
caecum and appendix and the first 20 cm
of colon which formed a knuckle in the
pelvis. The right leaf of the mesentery
then became continuous with the right
leaf of a very attenuated pelvic mesocolon
whereas the left leaf continued to anchor
an ascending limb of colon to the posterior
body wall in the left half of the abdominal
cavity. It is intended that a more detailed
account of these and the associated vascular arrangements should appear elsewhere.
397
398
PAULA M . WILSON
Fig. 1 Photograph showing general disposition of intestine and related structures : note
small bowel to right, large bowel below and to left. ST,stomach; D, duodenum; P, pancreas;
K, kidney; I, inferior vena cava; S, spleen.
U N U S U A L DUODENO-PANCREATIC RELATIONSHIPS
Duodenum (see figs. 1 and 2 )
From the pylorus, which was situated
2.5 cm to the left of the midline at the
level of the second lumbar vertebra, this
part of the bowel formed a U loop with an
upward concavity, 13 cm in length, in
which rested the head and part of the body
of the pancreas. This loop was related anteriorly to the liver and gall-bladder, posteriorly to the aorta, the origin of superior
mesenteric artery and the inferior vena
cava, and inferiorly to coils of small intestine; superiorly the whole concavity was
occupied by the pancreas.
A hairpin bend at the end of the U loop,
related posteriorly to the inferior vena
cava, led into a vertical descending limb of
bowel 10 cm in length; this in turn was
continuous with a further 10 cm loop with
concavity directed downwards, which continued into the coils of bowel suspended in
the mesentery.
The exact site of the duodeno-jejunal
junction defies anatomical definition; it
can be presumed to be distal to the U
loop, but whether it is at the end of this
loop or of the succeeding vertical limb is
uncertain. Circular folds were more
marked in the vertical limb than in the
399
U loop distal to the ,duodenal papilla.
Brunner glands were not found in the U
loop distal to the papilla; this is apparently
a common finding, but in this specimen the
papilla lay only 5 cm from the pylorus,
instead of the usual 8-10 cm. No ligament of Treitz or fibrous bands related to
the various flexures in the proximal small
bowel could be demonstrated.
Pancreas
The pancreas, measuring 9 cm in length,
lay in the concavity of the U loop of duodenum, to which it was firmly connected by
peritoneum and blood vessels; to the left it
continued above the pylorus. The common bile duct lay on the anterior aspect of
the head of the pancreas, reaching the
superior border of the U loop of duodenum
just proximal to its point of maximum
concavity 5 cm from the pylorus. The hepatic artery formed at first a posterior and
inferior and thereafter an anterior relation of the pancreas (see below). The POTtal vein, commenced posterior to the head
of the pancreas before entering the right
free margin of the lesser omentum.
The pancreas was related anteriorly to
the liver and anterior abdominal wall and
Fig. 2 Diagram illustrating arrangement of proximal small bowel and pancreas - ante.
rior view.
400
PAULA M. WILSON
inferiorly to the duodenum, the pylorus,
and the beginning of the lesser curve of
the stomach; behind the lesser curve the
junction ,of ascending and transverse colon
just reached the tail of the pancreas. Superiorly it was related to the liver, the
structures in the right free border of the
lesser omentum intervening. Posteriorly
were the inferior vena cava and renal
veins, the aorta with its upper branches,
the crura of diaphragm, the coeliac ganglia and plexus, and the splenic vein; the
tail did not reach the hilum of the left
kidney.
Peritoneal relations of pancreas
and duodenum
Because of the position of the pylorus,
the greater omentum lay wholly to the left
of the midline. The lesser omentum was
normal in all respects; to the right of the
pylorus its anterior layer enclosed the U
loop of duodenum and the pancreas, so
that these structures were mobile and
could be flapped up or down. Reaching
the vessels on the posterior body wall the
peritoneum clothed them in the usual way,
and, to the right, firmly anchored the
flexure and vertical limb of small bowel
following the U loop as well as the succeeding loop. This loop had peritoneum
anteriorly, inferiorly, superiorly and postero-superiorly so that a deep fossa was
formed above it, between it and the lower
pole of the left kidney. At the distal end
of this loop the peritoneum covering it
became continuous with the mesentery of
the small bowel.
Blood supply of pancreas
and duodenum
The hepatic artery, (see fig. 3 ) arose in
common with the superior mesenteric artery, n'ot from the coeliac trunk. It passed
downwards behind the pancreas and then
insinuated itself between the lower border
of the pancreas and the upper surface of
the duodenum and returned upwards anterior to the pancreas to gain the right
free border of the lesser omentum, coming
to lie on the left side of the common bile
duct. This normal relation to the duct is
considered to establish the identity of this
vessel as the true hepatic artery and not a
right accessory hepatic artery.
Fig. 3 Photograph of dissection showing arterial distribution in relation to posterior aspect of
duodenum and pancreas. Note hepatic artery ( H ) arising in common with superior mesenteric
artery ( S M ) . ST, stomach; D, duodenum.
UNUSUAL DUODENO-PANCREATIC
On the posterior aspect of the pancreas
the artery gave off the following branches
from its left side:
(1) Inferior pancreatic branch from
which arose an accessory gastro-epiploic
artery; these vessels gave branches to the
posterior aspect of the head, neck, body
and tail of the pancreas - the inferior
branch running near the lower border of
the pancreas and finally sinking into the
tail; ( 2 ) right gastro-epiploic artery in its
usual position; ( 3 ) superior pancreaticoduodenal artery arising from the left side
of the vessel just before it slipped between
pancreas and duodenum; this crossed behind it giving branches to the pancreas
and foregut as well as the mid-gut loop,
its terminal branch linked with the inferior pancreatico-duodenal vessels in the
concavity of the distal part of the U loop
of duodenum. ( 4 ) Right gastric artery.
From the right side of the hepatic, two inferior pancreatico-duodenal branches supplied the posterior aspect of the head of the
pancreas and the distal part of the U loop
of duodenum. On the anterior aspect of
the pancreas the hepatic artery gave off
small branches, mostly from its right side,
supplying the pancreas and duodenum.
Fig. 4
RELATIONSHIPS
40 1
The vertical limb of small bowel following the U loop of duodenum was fed by
right-sided jejunal branches of the superior mesenteric artery, a point in favor of
locating the duodenso-jejunalflexure at the
end of the U loop.
Arrangement of ducts
(see figs. 4 and 5)
The common bile duct lay on the anterior aspect of the pancreas to the right of
the hepatic artery, and entered the wall of
the duodenum on its posterior aspect. The
greater duodenal papilla was located on
the posterior wall of the duodenal lumen,
5 cm from the pylorus, just proximal to
the lowest point of the Concavity of the U
loop. The termination of the common bile
duct was joined on its right side by the
main pancreatic duct (duct of Wirsung)
which on dissection (see diagram and photograph) was found to drain the head and
then extend through the neck, body and
tail, its tributaries joining it in the characteristic herring bone pattern. A wellshown accessory pancreatic duct (duct of
Santorini) communicated with the main
duct at the junction of neck and body,
and then passed downwards, receiving
Pancreatic ducts displayed from behind. S, stomach; D, duodenum; P, pancreas;
M, main pancreatic duct; A, accessory pancreatic duct.
402
PAULA M. W I L S O N
Fig. 5
Diagram showing arrangement of pancreatic ducts viewed from anterior aspect.
ducts from the head, to open into the
lesser duodenal papilla, which was clearly
seen on the posterior wall of the duodenum
2 cm proximal to the greater papilla.
DISCUSSION
The anomalous features of this specimen
requiring explanation are thus :
(1) The situation of the pylorus to the
left of the midline; (2) the inverted relation of the duodenum and pancreas; ( 3 )
the relations of the bile and pancreatic
ducts; ( 4 ) the apparent shortness of the
functional duodenum; (5) the course of
the hepatic artery. "one of these features,
except possibly the first (Kanagasuntheram, '60) are regularly associated with
second stage arrest of intestinal rotation.
Indeed, none of the cases of second stage
arrest which I have found described appears to have presented duodeno-pancreatic relations identical with those observed
here although it must be remarked that
some of these reports are very uninformative on such points as the situation of the
duodenal papilla or even the precise relation of pancreas to duodenum.
On dissection the main pancreatic duct
was found to lie much closer to the anterior than to the posterior surface of the
gland which is the reverse of the normal
situation. This suggests that the duodenum has been inverted so that the anterior and posterior aspects are transposed
and that this reversal of surfaces has
also involved the pancreas. Three further
points in favor of this interpretation are :
1. The common bile duct crossed the
anterior, instead of the posterior surface
of the pancreas; 2. the lesser duodenal
papilla (the orifice of the accessory pancreatic duct of Santorini) is situated on
the posterior instead of the anterior wall
of the duodenum; 3. the pancreatico-duodenal vessels were predominantly distributed upon the posterior rather than the
anterior aspect of the gland. In fact, if the
duodenal U loop were rotated upwards
through 180°, carrying the pancreas with
it in its rotation, all these structures would
attain a relationship approximating to the
normal.
The direct cause of this inverted arrangement of the duodenum and pancreas
would appear to be the persistence of a
dorsal mesoduodenum enclosing the pancreas which allows the duodenum and
pancreas abnormal mobility. Instances of
such a persistence are recorded by Armstrong ('lo) and Reid ( ' 0 8 ) , in whose
cases the pancreas was palpable between
the leaves of the duodenal mesentery, and
by Wagstaffe ('23) who has described a
duodenum which had turned a half circle
in a clockwise direction because i t was
unduly mobile. This situation is aggravated by the compression of the transverse
colon into the left half of the abdomen, so
UNUSUAL DUODENO-PANCREATIC RELATIONSHIPS
that the anchoring attachments of the
transverse mesocolon to the duodenum and
pancreas are wanting.
If this were the full explanation however, it might be expected that the inverted
relationship of duodenum and pancreas
would be the rule in cases of second stage
non-rotation, which is clearly not the case.
Some other causative factors must therefore be invoked. It may be suggested that
these factors are in some way related
either to the abbreviation of the functional
duodenum or to the aberrant course of the
hepatic artery. Support for these suggestions are furnished by the somewhat similar conditions observed by Brash and
Stewart (’19) in association with a quite
different major anomaly, viz., reversal of
situation of the abdominal fore-gut derivatives accompanied by normal rotation of
the mid-gut loop. In their case:
( a ) The duodenum was apparently
shortened, judging by the distance of the
duodenal papilla from the pylorus; ( b )
the pancreas. only 7.5 cm in length, lay
above the pylorus; (c) the hepatic artery
arose fnom the superior mesenteric artery
and encircled the pancreas traversing a
wide gap between the lower border of the
pancreas and the upper border of the
duodenum. According to Woodbourne (‘62)
the common hepatic artery arises from the
superior mesenteric artery in ‘only a small
percentage of cases, so the coincidence of
this anomaly in association with the pancreas lying superior to the duodenal loop
and a shortening of the duodenum, may
be of considerable significance.
Abnormal configurations of the duodenum are well annotated with descriptive
drawings by Papez (’21 ), who summarized
his own findings and those of Bryce, Eddy,
Clermont, Reid and Roud; of these Reid’s
(fig. 6 ) most closely approximates to ours,
as the duodenal loop was mobile and if
turned down would be similar in many
respects. No record of the openings of
bile and pancreatic ducts was made in
their case. Dott (’23), Ladd (’33), Armstrong (’lo), Anderson (’23), Eddy (’12)
and others have all described the so-called
“vertical” duodenum (fig. 7) lying entirely
to the right of the midline and, if unfettered by a Ladds band, tending to course
down the right paracolic gutter to join the
403
small bowel. Except for its proximal inch
the duodenum in our case lay entirely to
the right of the midline. Goodwin (’15)
gave a description of a U shaped loop of
duodenum with its concavity upwards the limbs of the U in his diagram were
approximated to each other and the pancreas lay posterior to the left limb of the
U. No mention is made of the orifices
pertaining to bile and pancreatic ducts.
The formation of the duodenal curve,
as it is most commonly encountered, has
intrigued many investigators, who have
been able to base their work on the broad
foundations laid by Treves (1885), Mall
(1898), Frazer and Robbins (’l5), and
Dott (’23). Briefly, growth of the duo-
Fig. 6 Diagram of anomalous duodeno-pancreatic relationships described by Reid (’08),
from Papez (’21).
Fig. 7 Diagram of “vertical” duodenum, from
Papez (’21).
404
PAULA M. WILSON
denal segment of bowel between the fifth
and eleventh weeks of embryonic life is
accompanied by change in position and
growth of surrounding organs and an
"urge" to rotate shown by the terminal
duodenum. As the curve becomes established peritoneal adhesions and the ligament of Treitz help to stabilize its final
shape. Some of the contributions to this
field of enquiry will now be mentioned.
Frazer's contention that the growth of
the head of the pancreas was the most
important factor in determining the development of the duodenal curve cannot,
in view of Brash and Stewart's ('19) and
our own case of a shortened duodenum
associated with an abbreviated pancreas,
be entirely waived although Hunter ('26),
quoting Carner and others, states that
certain animals, including the pig, show
a well marked duodenal curve although
the head of the pancreas does not develop.
He concludes that the pancreas grows
along planes of least resistance and is
moulded by neighboring organs; it does
seem possible h,owever that when the pancreas grows within the C curve of the
duodenum it may help to lengthen it.
A major factor in the establishment of
the curve appears to be the migration of
the terminal duodenum beneath the superior mesenteric vessels, to the left of the
midline, which also results in the root of
the mesentery crossing the third part of
the duodenum. Snyder and Chaffin ('54)
found that in addition to the usual 90"
anti-clockwise rotation of the pre-arterial
segment which begins at the 10 mm ( 5
week) stage, the duodeno-jejunal loop by
the 25 mm ( 7 week) stage, had already
passed beneath the superior mesenteric
artery. When it is recalled that the second
stage of rotation only begins at the 40 mm
(10 week) stage it is clear that this important migration must occur during the
first stage and Kanagasuntheram ('60)
further postulated that failure of this migration led inevitably to second stage arrested rotation of the mid-gut 10,op as was
seen in our case.
ACKNOWLEDGMENTS
I gratefully acknowledge help, advice
and encouragement so freely given by
Professor Wells and wish also to thank
Mr. Coetzee for his artistic handling of my
drawings.
LITERATURE CITED
Anderson, J. H. 1923 Abnormalities of the Duodenum. Brit. J. Surg., VoZ. 10: 3 1 6 3 2 1 .
Armstrong, G. E. 1910 Abnormal position of
Duodenum. Trans. Amer. Surg. Assoc., 28:
299-307.
Brash and Stewart 1919 Partial transposition of
Mesogastric Viscera. J. Anat., 54: 2 7 6 2 8 6 .
Bryce, T. H. 1899 A rare abnormality of curvature of duodenum. J. Anat. and Physiol., 33:
27. Proceedings of the Anatomical Society
of Great Britain and Ireland.
Dott, N. M. 1923 Anomalies of Intestinal Rotation; their Embryology and surgical aspects,
with report of five cases. Brit. J. Surg., 11:
251-286.
Eddy, N. B. 1912 Arrested development, Pancreas, Intestine. Anat. Rec., 6: 319-323.
Frazer, J. E., and R. H. Robbins 1915 On
factors concerned in causing rotation of intestine. J. Anat. and Physiol., 50: 75-110.
Goodwin, B. 1915 A case of partial failure of
torsion of the intestinal loop, with a summary
of recorded cases. Studies in Anatomy, University of Birmingham ('15) (published by
Cornish Bros.)
Hunter, R. H. 1926 A contribution to the
development of the duodenum. J. Anat., 61:
206-232.
Kanagasuntheram, R. 1960 Some observations
on the development of the human duodenum.
J. Anat., 94: Pt. 2, 231-240.
Ladd, W. E. 1933 Congenital obstruction of the
small intestine. J. Amer. Med. Assoc., 101:
1453-1458.
Mall, F. P. 1898 Manual of Human Embryology
('12), 2: 1st ed., 318-322.
Papez, J. W. 1921 Abnormal position of Duodenum. Anat. Rec., 21: 309-321.
Reid, D. 1908 Imperfect torsion of the intestinal
loop. J. Anat. and Physiol., 42: 320-325.
Snyder, A. H., and L. Chaffin 1954 Embryology
and pathology of the intestinal tract: presentation of 40 cases of malrotation. Ann. Surg.,
140: 368-380.
Treves, F. 1885 Lectures on the anatomy of the
intestinal canal and peritoneum i n man. Brit.
Med. J., I: 4 1 5 4 1 9 .
Wagstaffe, W. W. 1923 Case of abnormal duodenum. J. Anat., 58: 178-179.
Woodbourne, R. T. 1962 Segmental anatomy of
the liver: blood supply and collateral circulation. Univ. Michigan Med. Bull., 28: 189-199.
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