Somatic and Portal Venous System in the Recto-Uterine Pouch

116

ANASTOMOSES BETWEEN THE RECTAL AND UTERINE VEINS FORMING A CONNEXION BETWEEN THE SOMATIC AND PORTAL VENOUS SYSTEM IN THE RECTO-UTERINE POUCH

BY E. G. WERMUTH

THE existence of anastomoses between the somatic and portal venous systems in the region of the rectum has been knownfor a long time. The question as to whether there are anastomoses between the rectal and uterine veins above the levator ani muscle was raised, first, by clinical and pathological observations in cases of pylephlebitis of the liver due to purulent endo- and parametritis, and secondly, by the presence of a white discharge from the uterus in some cases of congestion of the portal system. Before describing my own investigations it may be useful shortly to review the literature dealing with the veins in the female pelvis in general and particularly that dealing with the venous connexions between the genital tract and the rectum. Rauber-Kopsch, Sieglbauer, Spalteholz and Tandler recognize the following venous plexuses in the pelvis, named according to the organs on which they lie: pudendal plexus (in front of the bladder), vesico- vaginal plexus, utero-vaginal plexus, haemorrhoidal plexus. The first three plexuses are in wide communication and form a unit from which the haemorrhoidal plexus is distinguished because it flows to the portal vein and has no wide connexion with the other pelvic plexuses (see below under Peham- Amreich). Further details about the veins of the rectum and uterus are given by Poirier-Charpy. The main flow of uterine blood goes to the hypogastric vein through the utero-vaginal plexus and also to the ovarian vein which is a direct cranial continuation of the utero-vaginal plexus. There is another path caudally to the internal pudendal vein through the pudendo-labial plexus, and there is a smaller path to the veins of the lower abdominal wall by means of the round ligament of the uterus. The veins of the rectum as far as the anus flow into the portal vein through the superior haemorrhoidal vein. The latter originates in the venous plexus of the rectal columns of Morgagni, from which come two main veins (left and right) running in the submucous tissue of the rectum for 5-6 cm., then breaking through the muscular wall in order to form the external haemorrhoidal plexus which lies under the serosa of the ampulla recti on both sides. They then end in a vein on each side, joining with the superior haemorrhoidal vein. The Anastomoses between the Rectal and Uterine Veins 117 anastomoses of the above venous region are described by Poirier-Charpy as follows: (1) The inferior haemorrhoidal veins. These are very small vessels in the subcutaneous tissue around the lower margin of the external anal sphincter muscle. They receive some blood from the venous plexus in the rectal columns and passing through the ischio-rectal fossa establish connexions with the internal pudendal vein. (2) Anastomoses laterales. These are several veins arising from the rectal wall 5-6 cm. above the anus. Together with some vaginal, veins they form a so-called intermediate haemorrhoidal vein on each side, flowing into the hypogastric vein. The name and significance of the intermediate haemorrhoidal vein vary greatly throughout the literature. Authors using the. Jena nomenclature do not mention this name nor an analogous vein. Other authors show remarkable differences in the description of the intermediate haemorrhoidal vein. Corning calls it a paired vessel breaking through the rectal wall in the sphincter region without relation to the genital veins in its further course. The original picture Corning is referring to (which is also used by Rauber-Kopsch) is given by Nuhn and shows "two veins cut off just before they join the hypogastric vein and collecting all veins from the pelvic plexus ". There is a certain resemblance to Poirier-Charpy's intermediate haemorrhoidal vein, so far as the latter also collects the blood from the rectum and the genital organs. According to Nuhn, however, it appears that the entire rectal blood flows to this vein and therefore to the hypogastric vein, but this is denied by all the other authors. They all agree that the main flow of the rectal blood goes to the portal vein. Peham-Amreich says that all veins of the female urogenital tract are in wide connexion with those of the rectum and form practically a single large plexus. For these reasons the ligature of the main veins leading to the hypogastric vein does not always prevent the spread of septic thrombophlebitis, because the way to the portal vein still remains open. Although the pictures of Peham- Amreich show much detail, they do not show any path to the portal vein as mentioned above, but the pararectal space where the respective anastomoses should be expected is shown as containing no anastomoses at all. Kownatzki gives a very detailed description of the female pelvic veins, but does not mention an intermediate haemorrhoidal vein or any corresponding vein. From the literature, therefore, it appears that the relations between the rectal and genital veins are not certain and the statements of the various authors con- tradictory. Further, it seems that a wide communication between the external haemorrhoidal plexus and the utero-vaginal plexus, similar to the connexion between the latter and the vesical plexus, is usually denied. The object of these investigations was to discover the exact relations of the venous anastomoses between the genital and rectal plexuses, and particularly to seek for evidence of direct venous connexions between the rectum and the uterus. 118 E. G. Wermuth

MATERIAL AND TECHNIQUE The results of investigating blood vessels in the cadaver by injection methods do not necessarily reflect the circulatory conditions in the living subject, for although a vessel may fill with the injection material it does not follow that in the living the blood would fill the vessels to a similar degree under physiological conditions. An example of this can be seen in investigations on the rami communicantes in the circle of Willis, and the difficulties are even greater in the case of the veins where, to reproduce in the cadaver all the conditions on which venous flow depends, is almost impossible, especially as slight changes may result in pathological effects in the living. This must be borne in mind in interpreting the results of venous injections in the cadaver. It is possible, however, to draw conclusions as to the state of affairs in the living if several specimens are injected from different directions and give con- sistent results. The investigation was carried out on fourteen bodies a few hours after death. In twelve cases a retrograde injection through the superior haemorrhoidal vein was used. The pelvis as a whole was separated from the body and a cannula inserted into the superior haemorrhoidal vein as it lay in the mesentery of the sigmoid colon. Warm water was first run into the cannula, and then the injection material by means of high pressure syringes operated by screwing. The filling of the internal haemorrhoidal plexus was watched by a rectal speculum. As soon as this plexus became filled and a constant pressure felt upon screwing the syringe, the injection was considered sufficient. In two cases an injection was made in the natural direction through the dorsal vein of the clitoris. In these cases the amount of material injected was judged entirely by the pressure in the syringe. In some cases the hypogastric veins on one or both sides were also injected. If anatomical preparations are required, the most suitable material for injection is "Revertex", which is a rubber derivative in the form of a thick fluid which remains elastic. Stained with cinnabar it gave a good shadow with X-rays. In some cases specimens were cleared by Spalteholz's method, and in these cases the injection material consisted of Teichmann's injection material or a mixture of water-glass and kaolin. The latter took much less time to pre- pare. In addition, Tandler's cold fluid gelatine was tried, stained with ultra- marine blue; this material however, although sufficiently fluid to fill capillaries, was not suitable for macroscopic specimens on account of its small elasticity. After injection the tissue was preserved by the injection of 2 % formalin into the arteries. The " Revertex " specimens were transferred to 70 % alcohol, which causes the pelvic connective tissue to remain much softer than does formalin. The Teichmann specimens were kept in 2 % formalin, and the kaolin specimens in absolute alcohol before clearing by the Spalteholz method. The clearing process should begin by the removal of pigment with peroxide of hydrogen, and for this purpose it is of advantage to remove -the pelvic viscera Anastomoses between the Rectal and Uterine Veins 119 from the pelvis. After dehydration in ascending concentrations of alcohol the specimens are kept permanently in a special solution of chaulmoogra oil and benzyl benzoate, which renders the entire specimen more or less transparent. It is of advantage to have the specimen as thin as possible. In spite of every care in preservation it was not possible to avoid the presence of some gas bubbles. RESULTS OF THE INVESTIGATIONS Four typical cases are described, the findings in the other cases being very similar. All anastomoses between the rectal veins and tributaries of the hypogastric vein are in a space which may be referred to as the pararectal space. This space is filled with connective tissue (" tela urogenitalis " of Tandler) and is bounded medially and caudally by the rectum, laterally by the hypogastric and uterine veins, cranially by the recto-uterine ligament, and medially and cranially by the peritoneum of the pouch of Douglas. The veins are described according to the direction of injection and not according to the direction of blood flow in them. In the descriptions of the veins, in some cases the calibre is indicated by accompanying measurements. Cases 1-4 were injected through the superior haemorrhoidal vein. Cases 5 and 6 through the dorsal vein of the clitoris.

Case 1 (Fig. 1) The superior haemorrhoidal vein lies in the pelvic mesocolon and comes into relation with the upper part of the rectum on its left posterior wall. There it divides into a right and left main branch (5 mm. in diameter). The right branch reaches the right side of the rectum by going around the posterior wall at the level of the second sacral vertebra. Each of the main branches divides into a lateral branch (A, 5 mm.), and a medial branch (B, 3 mm.), approximately at the level where the peritoneum is reflected from the rectum to the posterior fornix of the vagina. The lateral branches on both sides continue the direction of the main branch by running along the rectum. On the right side the medial branch (B) divides into numerous small branches penetrating the rectal wall. On the left side the medial branch divides into two branches, medial and lateral. The former continues the direction of the main medial branch (B) while the latter continues laterally and caudally to communicate with the main lateral branch (A). In spite of the names given in the literature, the superior haemorrhoidal vein does not form a plexus comparable with other pelvic venous plexuses. The superior haemorrhoidal vein communicates with the hypogastric vein, the uterine veins, and the utero-vaginal plexus by the following anastomoses which are described in a cranio-caudal direction. Right side. (1) A vein (1 mm. in diameter) runs cranially after arising from the main branch at the level of the second sacral vertebra, and enters the hypogastric vein at the arcuate line. 120 E. C. Werrmuth (2) A vein (1 mm.) arises from B and runs laterally. After receiving numerous small subserous veins, it enters the hypogastric vein 2 cm. more peripherally than (1).

Peritoneum cut edge"

--Cervix uteri

Recto-uterine X thri vei ligament------uUterine vein 4

A rn~ .o ;, ;; ------B n II ~~~~~~~~~~~~~2

J -.. ~~Hypogastric

Right main Reflexion of the bac Peritonleufl Rectumle(u1

Fig. 1. Peritoneum of the pouch of Douglas removed, displaying the cervix and the right side of the body of the uterus, as well as the retroperitoneal portion of the rectum. Recto-uterine ligament preserved on the left side and drawn dorsally. On the right side the pararectal space is widely opened. Left side: A, B, I, II, branches of the superior haemorrhoidal vein. 1, anastomotic vein disappearing in the recto-uterine ligament. 2, 3, anastomotic veins passing dorso-ventrally to the uterus. Right side: A, B, branches of the superior haemorrhoidal vein. 1-7, anastomoses between the rectal veins and branches of the hypogastric vein passing laterally and cranially (not figured on the left side). 8, anastomotic vein passing dorso-ventrally to the uterus.

(3) Another vein (1 mm.) comes directly from the posterior wall of the rectum and not from any visible branch of the superior haemorrhoidal vein. Passing cranially it reaches the uterine vein just before the latter joins the hypogastric vein. (4) A vein (1 mm.) coming from A, enters the hypogastric vein 1 cm. peripherally from the junction with the uterine vein. Anastomoses between the Rectal and Uterine Veins 121 (5) A vein (1 mm.) is formed by the junction of two equal tributaries arising from A and B. It splits into two short branches one of which enters the uterine vein a little peripheral to the junction of (3) with the uterine vein. The other branch enters a vessel which lies caudal to the uterine vein and which runs parallel to it towards the lateral border of the uterus. (6, 7) Two 1 mm. veins arising from A. They also enter the vein mentioned above which runs parallel with the uterine vein. (8) A 1 mm. vein formed by the junction of two equal tributaries which arise from A and B. It passes dorso-ventrally and reaches the utero-vaginal plexus on the lateral margin of the uterus. Left side. (1) A vein (0.5 mm.) arises from II and breaks up into a fine network which disappears in peritoneal tissue of the recto-uterine fold. (2) A vein, 1 mm. in diameter and 2-5 cm. in length, arises from II. It passes directly ventrally and a little laterally to the lower end of the lateral margin of the uterus, there entering the utero-vaginal plexus. (3) Two small veins (0.5 mm.) coming from both I and II, join and form a vein, which passes cranially and disappears in the recto-uterine fold, where the injection stops. Case 2 (Fig. 2) The branches are similar to case 1 with the exception that here the left medial branch (B) divides into three branches; a lateral branch (I), an intermediate (II) and a medial (III). This division takes place on the lateral rectal wall about 2 cm. caudal to the peritoneal reflexion. The following anastomoses were found: Right side. (1) A branch, 3 cm. long and 1 mm. in diameter, arises from B. It runs dorso-ventrally and enters the lateral part of the posterior vaginal fornix. Just before entering the fornix it gives a fine branch which runs medially to the anterior rectal wall and enters it. Left side. (1) There is a vein, 1 mm. in diameter and 2 cm. long, running directly dorso-ventrally and entering the lower part of the lateral margin of the uterus. This vein is formed by the junction of two veins. One of them arises from II just behind the point of division of B, the other from the branches formed by the breaking up of III. (2) There is a short vein (1 mm.) passing laterally and cranially to the utero-vaginal plexus. It arises from I, 3 cm. caudal of the point of division of B. Further anastomoses were found on both sides leading laterally and cranially to the veins on the pelvic wall. The arrangement was very similar to 122 E. G. Wermuth veins 1-4, described on the right side of case 1, and are not described because the main stress is laid on anastomoses which pass directly to the uterus.

Cut cdge of the peritoneum

Uterine vein7 I.PtPT Uterine veili (cut) Levator adliio - _.Cervix uteri

Elevator amll ;c-rcut. edgre -k--,..l ehiorectal B------B IReflexionl of the peritoneumn

flIypogastrie vein (cut) lH'ivpogstric vejln (eut)

Fig. 2. Peritoneum of the pouch of Douglas removed on both sides. Uterine and hypogastric veins cut on both sides. Rectum and uterus drawn apart. On the right side coronal section through the levator ani and ischiorectal fossa (latero-cranial anastomoses between rectal and hypogastric vein not figured). Left side: B, I, II, III, branches of the superior haemorrhoidal vein. 1, 2, anastomotic veins passing dorso-ventrally to the uterus. Right side: B, branch of the superior haemorrhoidal vein (further branches not described). 1, anastomotic vein passing dorso-ventrally to the uterus.

Case 3 The situation and branches of the main veins are similar to the previous cases. Anastomoses are as follows: Right side. No anastomoses from the external branches of the superior haemorrhoidal veins. However, there were found two anastomoses coming from remarkable venous arches. These arches are formed by veins (1 mm.) which leave the Anastomoses between the Rectal and Uterine Veins 123 rectal wall, form a subperitoneal arch, giving an anastomotic branch from their convexity and returning to the rectal wall near where they arose. (1) Such a venous arch leaves and re-enters the rectal wall at the level of the third sacral vertebra. It gives a branch, 1 mm. in diameter and 2 cm. long, which passes dorso-ventrally and reaches the utero-vaginal plexus 05 cm. laterally to the lower end of the lateral margin of the uterus. (2) A similar vein which enters the lateral margin of the uterus; it is shorter than (1) because it arises from a venous arch 2 cm. caudal to the first arch. Left side. (1) A vein, 1 mm. in diameter and 3 cm. in length, comes from a short medially directed branch of B. It passes dorso-ventrally to the lower end of the lateral margin of the uterus. Case 4 Here the hypogastric vein was injected as well as the superior haemorrhoidal vein. The arrangement of the main branches is similar to the previous cases, but the external branches make no anastomosis with the uterus. There is only one anastomosis arising directly from the rectal wall. A vein, 3 mm. in diameter and 2 cm. in length, emerges from the anterior rectal wall near the midline where the wall has no external veins. This is approximately 5-6 cm. above the anus. The vein passes in a dorso-ventral direction to the lower end of the left lateral margin of the uterus. Cases 5 and 6 These cases were injected through the dorsal vein of the clitoris. The urogenital venous plexus and the parietal veins were found to be completely filled with the injection material, but none of the rectal veins was filled- neither the external nor the internal plexus, the latter being watched by a speculum. Further, no injected anastomoses were found comparable to those described in the previous cases. Observations using the Spalteholz method Specimens rendered transparent by this technique confirmed the results of anatomical dissection so far as the anastomoses passing to the uterus were concerned. Most of the cases resembled the findings in cases 1 and 2. Anasto- moses between the rectal veins and the veins of the pelvic wall (such as case 1, right side 1-4) could not be investigated because the organs had to be removed from the pelvis as a whole after injection through the superior haemorrhoidal vein. DISCUSSION As a fairly constant venous arrangement was found, the evidence from the above cases enables the following schematic summary to be made of the branches of the superior haemorrhoidal vein and its anastomoses. In the first 124 E. G. Wermuth place the name "external haemorrhoidal plexus" does not appear to be very suitable, for on the rectum the branches of the superior haemorrhoidal vein were distinct veins not differing greatly from those in other parts of the intestine. This distinguishes the so-called external haemorrhoidal plexus from the other pelvic venous plexuses. In the latter case, the name plexus is justified for the veins constituting them are wide blood-spaces anastomosing frequently and widely. For the lack of any other name, "external haemorrhoidal plexus" is retained in this paper The scheme of the branches is as follows. In the midline the anterior rectal wall is free from macroscopic veins, as the veins on both sides do not show any evident anastomoses on the external surface. The superior haemorrhoidal vein gives rise to a right and left main branch. The right branch passes behind the rectum to the right side. Then on each side the right and left main branch divides into a lateral (A) and medial branch (B), where the peritoneum is reflected from the rectum to the posterior vaginal fornix. Subsequent divisions vary slightly in different cases. In these divisions the veins do not diminish much in calibre and do not subdivide very greatly, but continue their course almost vertically downwards and all pierce the muscular wall of the rectum about 5-6 cm. above the anus. They then run in the submucous tissue. In the anastomoses between the somatic and portal venous systems in the pelvis two groups can be recognized: (a) Latero-cranial anastomoses. Veins passing laterally and cranially from the rectum to the hypogastric vein and its branches as described on the right side of case 1. There are usually four or five anastomoses on each side. They arise from branches A or B, but more frequently from the lateral branch A. (b) Dorso-ventral anastomoses. Veins passing dorso-ventrally which arise more caudally than the first group. There are one or two anastomoses on each side consisting of veins 2-3 cm. in length and 1 mm. in diameter arising from the rectum and running in the connective tissue of the recto-uterine ligaments (pararectal space) towards the lower end of the lateral margin of the uterus. Their origin from the rectum was fairly constant in seven cases. They arose from the tributaries of the main branches, more often from branch B. In case 3 two veins were found arising directly from the rectal wall apart from tributaries of the main branch. These showed remarkable venous arches. In case 4 there was only one, but a much bigger, anastomosis arising directly from the anterior rectal wall. These anatomical facts permit the discussion of the following questions: (a) What is the significance of these anastomoses in the normal and pathological blood flow in the female pelvis? (b) What is the relationship of these anastomoses to the well-known circumanal anastomoses? Owing to the disadvantages of the injection methods already mentioned, a complete answer to these questions cannot be given here. Of the first question it may be said that the venous return from pelvic organs is extremely variable. Anastomoses between the Rectal and Uterine Veins 125 It is influenced by physiological filling of the rectum and bladder, pregnancy, and pathological changes such as tumour formation, inflammation, etc. These produce greater changes in the blood flow of the pelvis than similar conditions in the abdomen. Pelvic blood flow is affected more than abdominal blood flow in such circumstances because of the rigidity of the pelvic walls. The wide pelvic venous plexuses are to some extent able to prevent obstruction to the venous return, as compression of a plexus is more difficult than of a single vein, and also the wide and frequent anastomoses of a plexus would allow the blood to find some alternative route. On the other hand, plexuses have the disadvantage that they slow the blood flow because of their large total diameter, thereby further decreasing the speed of flow which is already low due to the small pressure difference between peripheral veins and the more central trunks. Plexuses are found in relation to the urogenital system, but these drain into the inferior vena cava where the difference in pressure from that in the peripheral veins is sufficient to overcome the slowing action of the plexuses. The rectal veins, on the other hand, represent the most peripheral portion of the portal system which has no valves, and where the pressure differences are much less than in the caval system. For this reason, in the rectum the further slowing of the blood flow by a venous plexus has been avoided. Cases 5 and 6, which were injected in the direction of normal blood flow, give evidence that blood does not flow into the rectal veins from the urogenital organs as long as conditions are normal. Although the anastomoses described form a possible route from the uterus to the rectum, normally the blood flow in them is negligible. This might be due to valves in the anastomotic veins, or to their small size compared with the veins of the urogenital plexus. The anastomotic veins might become important, however, if flow in the caval system were impeded by any cause. Furthermore, infection might spread along these anastomotic veins in spite of their negligible blood flow. On the other hand these anastomoses might become functional in general portal congestion (cirrhosis of the liver, thrombosis of the portal vein, tumours, etc.), or in local obstructions of the venous outflow from the rectum. These congestions were imitated by injection of the superior haemorrhoidal vein, when the recto-uterine venous anastomoses were demonstrated. In discussing the second question, it is known that the degree of haemor- rhoid formation does not correspond to the degree of portal obstruction in cirrhosis of the liver. This may be accounted for by a large formation of varicosities around the cardia of the stomach which act as the main path for relief of the congested portal system. There is no doubt, however, that rectal anastomoses also play a part in the relief of portal congestion, but it seems that this relief is mainly provided by intrapelvic venous anastomoses, rather than by the circumanal. This is suggested by those cases where the superior haemorrhoidal vein was injected, thus imitating artificially the conditions of portal congestion. In these cases the intrapelvic anastomoses as well as the 126 E. C. Wermuth internal haemorrhoidal plexus were well filled, but no injection could be found in the circumanal anastomoses in the ischiorectal fossa. The final confirmation of the importance of the intrapelvic venous anastomoses can only come from investigations on cases of established portal congestion. As a rough means of investigation at autopsy a useful method would be to examine the recto-uterine pouch for enlarged veins, and also to examine the veins of the pararectal space. However, an accurate investigation is only possible by the use of some injection and dissection technique.

SUMMARY 1. A description is given of the venous anastomoses between the uterus and the rectum, based on the findings in several normal pelves. These con- stitute previously undescribed anastomoses between the somatic and portal venous systems. 2. In normal and in pathological conditions the significance of these anastomoses is discussed in the pelvic blood flow, and in the spread of infection from the uterus and parametrium towards the portal vein. 3. In portal congestion it is suggested that these anastomoses are of more importance than the circumanal anastomoses.

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