Arch Dis Child: first published as 10.1136/adc.41.220.597 on 1 December 1966. Downloaded from Arch. Dis. Childh., 1966, 41, 597. The Ductus Venosus and the Mechanism of Its Closure* W. W. MEYER and J. LIND From the Paediatric Clinic, Karolinska Sjukhuset, Stockholm, Sweden, and the Institute of Pathology, Mainz, Germany Although recognized since Vesalius as one of the Stern, andWegelius, 1964; Lind, 1959,1963). From distinguishing features of the foetal circulation, the the angiograms it can be seen that the big umbilical precise function of the ductus venosus is uncertain. vein upon entering the liver gives off branches to the Anatomically, it provides a direct connexion between left and quadrate lobes of the liver, which are rela- the umbilical vein and the inferior vena cava. tively large in foetuses and newborn infants (Fig. 1). Functionally, it represents a bypass through which Most of the umbilical flow is, however, divided part of the oxygenated umbilical blood flows higher up between the ductus venosus, which origin- directly into the inferior vena cava. However, what ates from the convex portion of the umbilical recess, portion of the umbilical venous blood flow passes and the portal sinus. The ductus venosus has a through the ductus venosus in the human foetus is straight course and runs in the same direction as the not yet known and has so far only been estimated intrahepatic part of the umbilical vein. It does not approximately. give off any branches. The inlet of the ductus Not all species of mammals possess a ductus venosus is opposite the outlet of the umbilical vein venosus at maturity; it disappears at an early stage in the umbilical recess, which results in a probably copyright. of gestation in the horse and the pig. Experiments preferential flow of the placental blood into the have shown that occlusion of the ductus venosus in ductus. At midterm its diameter measured from mature foetal lambs causes no significant change in the angiograms is about one-quarter to one-third of blood pressure, heart rate, or carotid oxygen that of the portal sinus and slightly less than that of saturation (Amoroso, Dawes, Mott, and Rennick, the stem of the portal vein. The portal sinus 1955). Its continued patency seems to be unneces- appears on the angiograms as a wide straight vessel sary for survival (Blanc, 1960). On the other hand, from which numerous branches originate (Fig. 1). its absence is occasionally associated with some The trunk ofthe portal vein opens in the portal sinus other malformations, and can cause portal hyper- and divides it into right and left parts, which after tension in the neonatal period (MacMahon, 1960). birth become right and left branches of the portal http://adc.bmj.com/ The findings concerning the structure of the vein. ductus venosus are contradictory and the mechanism It can further be observed that the ductus venosus of its postnatal functional clQsure is not yet satisfac- is visualized simultaneously with the portal sinus, torily explained; nor is there any agreement concern- while the hepatic veins, which drain the liver ing the time of closure after birth and the signifi- sinusoids, appear 1-1 second later. The degree of cance of its patency in the neonatal period of life. opacification is less dense, probably due to the slight We have therefore reviewed the published papers dilution of the contrast material. The main hepatic in the light of our own studies. veins return not only umbilical vein blood but also on October 5, 2021 by guest. Protected some blood that reaches the liver by the hepatic Angiographic Studies of the Function and artery. The venous return to the heart through the Closure of the Ductus Venosus inferior vena cava and its afferent venous channels In the living human foetus the function ofthe duc- is pulsatile. The contrast-loaded blood is stopped tus venosus has been demonstrated by angiocardio- during atrial systole-occasionally a reflux occurs- graphy carried out in connexion with therapeutic but during the following ventricular systole the abortions (Lind and Wegelius, 1949, 1954; Lind, blood rushes into the dilating atria. The proportion of umbilical blood that passes Received May 2, 1966. through the ductus venosus into the inferior vena * Supported in part by the Association for the Aid of Crippled cava during foetal development is not precisely Children, New York, N.Y., U.S.A., and the Swedish Medical Research Council to its Teratology Research Unit, Stockholm, known. In the lamb, flow through the ductus Sweden. venosus appears to be governed, according to 597 Arch Dis Child: first published as 10.1136/adc.41.220.597 on 1 December 1966. Downloaded from 598 Meyer and Lind copyright. FIG. 1.-Angiogram from a living human foetus of 19 weeks. Right anterior oblique projection. Contrast injection into http://adc.bmj.com/ the umbilical vein (uv) which is well opacified as are its liver branches. Portal sinus (ps) is clearly seen and there is retrograde filling of the portal vein. The portal trunk (pt) is seen to be narrower than the right and central part of theportal sinus. Much contrast medium is shunted through the ductus venosus (dv) directly into the inferior vena cava. Barron (1942), by the shape of the umbilical recess, since the diameter of the ductus venosus is only its walls containing smooth muscle fibres so arranged about one-seventh of the diameter of the umbilical that when they contract the cavity of the recess is vein. However, the relation of the two diameters is on October 5, 2021 by guest. Protected reduced and flow into the ductus diminished. In not decisive as to volume flow through the ductus addition, he observed a special band of smooth venosus, since this is also much influenced by the muscle fibres arranged in horse-shoe fashion at the peripheral vascular resistance of the liver. junction of the recess with the ductus. This band The magnitude of the shunt through the ductus he thought could contribute to functional closure of can be roughly estimated from our angiograms. In the duct. Barron (1944) states, on the basis of the great majority of cases studied, much opaque angiograms of Franklin, Barclay, and Prichard material is visualized in the heart before there is (1940), that in the foetal lamb only a small amount of appreciable opacification ofthe hepatic veins (Fig. 2). blood passes via the ductus venosus directly into the The impression from human foetal angiograms at inferior vena cava, whereas most of the umbilical mid-term is thus that the ductus venosus functions as venous blood supplies the capillaries of the liver; a low resistance bypass for the placental blood, and this is in agreement with the anatomical conditions, that a significant part of the placental venous return Arch Dis Child: first published as 10.1136/adc.41.220.597 on 1 December 1966. Downloaded from The Ductus Venosus and the Mechanism of its Closure 599 (one-third to two-thirds) reaches the heart through liver. This causes haemolysis and dissolves the this channel. post-mortem blood clots. Soon after perfusion Injection of contrast medium into the umbilical begins, the blood remnants are rinsed out of the vein in one newborn full-term infant before and liver, and it assumes a uniform pale yellowish colour. after the first breath demonstrated that the ductus Immersion of the liver in saline helps to avoid an venosus was widely open and permitted the passage additional increase of peripheral resistance due to of enough contrast medium to give visualization of distortion, which can occur when the liver is placed the left and right heart chambers and their efferent on a hard surface during the perfusion. vessels, i.e. the results correspond to those obtained The livers were perfused at room temperature by angiography at midterm. with saline via the umbilical vein at a pressure of In order to estimate the approximate distribution 20-30 cm. of saline (15-20 mm. Hg) after ligation of of the umbilical venous blood flow we have also the trunk of the portal vein. The fluid discharged undertaken some perfusion experiments in stillborn via the ductus venosus was collected, measured, and infants. The alterations which take place after compared with the total amount of saline that was death make such experiments hard to evaluate. injected into the umbilical vein. More than 50 Post mortem, the blood coagulation in the liver perfusions showed that 40-50% of the fluid injected vessels and especially in the liver sinusoids increases into the umbilical vein passed through the ductus the peripheral vascular resistance of the liver. venosus, whereas the other half reached the inferior Likewise, the insertion of a cannula in the proximal vena cava via the sinusoids of the liver. To what end of the ductus venosus narrows its lumen and extent these results can be applied to in vivo condi- increases its resistance also. However, the disturb- tions cannot yet be defined. Probably, the trans- ing effect of post-mortem blood coagulation can be port capacity of the ductus venosus in vivo varies diminished by deep freezing and thawing of the with the volume flow through the umbilical vein and the pressure gradient across the ductus venosus. Furthermore, the antenatal intermittent contrac- tions, i.e. temporary functional closures ofthe ductus copyright. venosus, which have been observed angiocardio- graphically in the foetal lamb (Franklin et al., 1940; Barron, 1942; Barclay, Franklin, and Prichard, 1942; Barcroft, 1946) and in the human foetus (Lind and Wegelius, 1954), could probably also influence the blood flow through this bypass. Many studies have been carried out to observe the behaviour of the ductus venosus following birth.