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