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Original Report |
1 Department of Pediatric and Fetal Imaging, Hôpital Debrousse, 29 Rue
Soeur Bouvier, Cedex 05, Lyon 69322, France.
2 Department of Radiology, Maternité A. Pinard, Nancy, France.
Received December 24, 2003;
accepted after revision April 22, 2004.
Address correspondance to G. Gorincour
(ggorincour{at}voila.fr).
Abstract
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CONCLUSION. Umbilicoportosystemic shunts encompass different congenital vascular abnormalities that should be recognized because they may interfere with fetal growth and circulation.
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For each case, the gestational age at diagnosis, anatomic findings, biometric data (head circumference, abdominal circumference, femoral length), hemodynamic data, associated anomalies, and fetal outcome were reviewed. Intrauterine growth retardation was defined as an estimated fetal weight below the 10th percentile following Hadlock's formula, and abdominal circumference was considered elevated if above the 95th percentile.
Hemodynamic changes were classified as absent, mild (hepatomegaly, cardiomegaly, moderate ascites), or severe (oligohydramnios, polyhydramnios, hydrops fetalis, fetal death).
Diagnosis was confirmed by pathology in four cases (including postmortem angiography, n = 3) and postnatal imaging data in three cases (including angiography, n = 2). Prenatal sonographic data were available for review in only four cases. We compared our cases with 42 prenatal cases of umbilicoportosystemic shunts reported in the literature [1–16].
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Umbilicoportosystemic shunts were associated with ductus venosus agenesis and persistent right umbilical vein in seven and four cases, respectively. Pathologic biometric changes included intrauterine growth retardation and increased abdominal circumference in six and four cases, respectively; these changes were absent in one case.
Hemodynamic changes were absent in three cases, mild in two cases, and severe in five cases. One case of polyhydramnios was not considered of hemodynamic origin because it happened in a polymalformative context that included esophageal atresia. Associated malformations were present in six cases. The fetal and neonatal outcomes were good in five cases. Fetal death occurred in two cases at 28 and 30 weeks' gestation. Pregnancy was terminated in one case. Eight newborns were delivered; among those, one was stillborn and two died in the first hours of life after labor was induced for fetal distress at 30 weeks' gestation.
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The Extrahepatic Umbilicoportosystemic Shunts
Direct entry of the umbilical vein into the right atrium (cases 1 and 11)
(Fig. 2) results from a lack of
incorporation of the umbilical vein into the hepatic bud and a persisting
direct drainage of the umbilical flow into the sinus venosus (future right
atrium). The absence of incorporation of the umbilical vein in the liver
reduces the intrahepatic vascular pressure, which explains the absence of
development of the ductus venosus. Our cases are similar to the 17 prenatal
cases reported in the literature
[1–4,
11–14].
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Umbilicoportosystemic shunts between the umbilical vein and the cardinal system result from pathologic anastomosis between the umbilical system and the anterior (superior vena cava) or posterior (iliac vein, renal vein, inferior vena cava) cardinal system (Fig. 3).
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Anastomosis with the subcutaneous vascular network.—As in the previous case, the shunt results from a lack of incorporation of the umbilical vein into the hepatic bud [18] and an arrest of direct return of the umbilical flow into the sinus venosus.
The umbilical flow is drained into a subcutaneous vascular network called "caput medusae" [19]. In case 2, this subcutaneous network joins the thoracic veins and then the superior vena cava.
Anastomosis with the iliac vein.—Direct anastomosis may result from a preexisting embryonic vascular anastomosis between the umbilical vein, which initially drains the inferior limb buds and from where the iliac veins originate, and the posterior cardinal system [18]. The ductus venosus was absent in our case (case 3). Ten similar cases have been reported in the literature [5, 6, 11–15, 20]. Of the nine prenatal cases, the ductus venosus was absent in six [5, 11, 13–15]. In the other cases, the ductus venosus was present, most likely due to its association with a second normal umbilical vein.
Indirect anastomosis occurs when the incomplete incorporation of the umbilical vein at the anteroinferior border of the liver results in retrograde flow into the vitellomesenteric trunk, which joins the cardinal system at the level of the iliac veins (Figs. 4A and 4B). We report three cases (cases 4–6) of umbilicoportomesentericoiliac anastomosis and did not find any reported case in the literature. In our three cases, a patent ductus venosus was present, which suggests a distal and delayed hemodynamic block leads to retrograde flow within the mesenteric veins.
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Anastomosis with the inferior vena cava.—Our cases 7 and 8 (Fig. 5) and the nine reported in the literature [7, 8, 11, 14, 21] illustrate the development of aberrant direct anastomosis between the umbilical vein and the inferior vena cava. Parumbilical vein and absent ductus venosus were noticed in both of our cases and in five cases in the literature. The ductus venosus was present and wide in three cases [14], whereas the portal vein was absent.
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Anastomosis with the superior vena cava.—Only three cases of this type of anastomosis have been reported in the literature, and both were via the azygos system [4, 13]. It is a direct anastomosis without any connection with a subcutaneous network, as in case 2.
The Intrahepatic Umbilicoportosystemic Shunts
Among intrahepatic shunts, one should differentiate two types. A direct
shunt is between the umbilical vein and a hepatic vein (case 9); three cases
have been reported in the literature
[13,
14]. An indirect shunt is via
an intrahepatic collateral network independent from the portal system (case
10) (Fig. 6). Two cases joining
the inferior vena cava and the right atrium have been reported in the
literature [9,
10]. In all cases, development
of the ductus venosus was absent.
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Umbilicoportosystemic Shunts, Absent Ductus Venosus, and Persistent Right Umbilical Vein
If a persistent right umbilical vein and absent ductus venosus are
associated with umbilicoportosystemic shunts, they should not be assimilated
to umbilicoportosystemic shunts. In our series, a persistent right umbilical
vein was encountered in only four cases (cases 7–10), and a ductus
venosus was present in three (cases 4–6). Jorgensen and Andolf
[22] reported four cases of
isolated ductus venosus agenesis and the persistent right umbilical vein now
is recognized as an anatomic variant that most often is isolated without any
associated malformation [23].
Its incidence in a low-risk population has been recently estimated as 1:526
[24].
Umbilicoportosystemic Shunts and Fetal Hemodynamics
In a healthy fetus, the ductus venosus represents a physiologic
umbilicoportosystemic shunt between a high-pressure umbilical system and a
low-pressure systemic system. The small caliber and the tapered proximal
extremity of the ductus venosus induce increased flow velocity that also may
be regulated by sphincteric activity, although the presence of a real
sphincter is controversial
[25–27].
The opening of the umbilical vein into the portal sinus is in-line with the
ostium of the ductus venosus; this alignment favors the preferential streaming
of oxygenated blood to the ductus venosus and thus regulation of oxygenated
venous return to the heart
[28]. Abnormal
umbilicoportosystemic shunts are a direct connection between a high-pressure
system and a low-pressure system. The absence of any flow regulation results
in increased pressure in the systemic system that may compromise fetal
hemodynamics.
In our series, fetal hemodynamic changes were severe in five cases (leading to termination of pregnancy in one case, fetal death in two cases, and postnatal death due to hemodynamic distress in two cases), mild in two cases (hepatomegaly or cardiomegaly), and absent in four cases. Review of our series and reported cases shows that fetal hemodynamic changes appear during the third trimester (> 25 weeks' gestation) and are more frequent in umbilicoportosystemic shunts joining the cardinal system. Conversely, no hemodynamic changes were encountered in cases of direct entry of the umbilical vein into the right atrium or in intrahepatic shunts; in case 11, polyhydramnios was postnatally considered as a consequence of esophageal atresia. The flow variations through the foramen ovale (decreased or constant) may explain the variable effects of the different types of umbilicoportosystemic shunts on fetal hemodynamics.
Umbilicoportosystemic Shunts and Fetal Biometry
In our series, two different biometric profiles were found in association
with umbilicoportosystemic shunts and hemodynamic changes: intrauterine growth
retardation (n = 6) and increased abdominal circumference (n
= 4). The decreased hepatic metabolism secondary to umbilical blood flow
reduction could be responsible for intrauterine growth retardation in five of
our cases of umbilicoportosystemic shunts. In the literature, intrauterine
growth retardation is reported in two cases of intrahepatic shunt
[9,
10]. Conversely, the increased
abdominal circumference suggests a false macrosomia, a consequence of a
congestive liver. This increased abdominal circumference appeared a few weeks
before the significant hemodynamic changes, as found in three of our four
cases with severe hemodynamic status. In the literature, an increased
abdominal circumference was found in three cases, two of which were associated
with severe hemodynamic distress
[5,
6].
Series do not always mention biometric profiles [11–15]; two cases of intrauterine growth retardation are reported, one with an umbilical vein joining the inferior vena cava [14] and the other one joining an iliac vein [12]. One should underline that no modification of the biometric profile was encountered in reported cases of direct entry of the umbilical vein into the right atrium except in our series in which the umbilicoportosystemic shunts coexisted with other severe malformations.
Umbilicoportosystemic Shunts and Associated Malformations
In our series, umbilicoportosystemic shunts were associated with other
malformations in six cases (54.5%). These malformations were mild in two
(cases 2 and 6) and severe and multiple in four (cases 1, 3, 5, and 11). Only
in case 11 did the associated malformation alter the outcome (stillborn;
vertebral, anal, cardiac, tracheal, esophageal, renal, and limb [VACTERL]
association). Among the 42 prenatal cases, of umbilicoportosystemic shunts
reported in the literature, associated malformations were present in 15 cases
(36%). In five cases, these anomalies were severe, including trisomy 18
syndrome [3,
12], severe brain
malformations [4], and cardiac
defects [15]. In the 10 other
cases, the anomalies occurred in the urologic tract (n = 2),
extremities (n = 2), and skeleton (hemivertebra, n = 2) and
included polysplenia (n = 1) and atrial septal defects (n =
5). In these 10 cases, pre- and postnatal outcomes were not altered.
Outcome Predictors of Umbilicoportosystemic Shunts
The anatomic type of umbilicoportosystemic shunt.—We would
like to emphasize that fetuses with direct entry of the umbilical vein into
the right atrium and with intrahepatic shunts have excellent hemodynamic
status and normal fetal growth (survival rate, 100%). By contrast, fetuses
presenting with umbilicoportosystemic shunts joining the inferior vena cava
(or one of its branches) or the superior vena cava are at potential risk for
hemodynamic distress (19/30 cases, 63%) and fetal or neonatal death. This risk
is high in those with umbilicoportosystemic shunts joining the iliac veins (or
bifurcation) (12/13 cases, 92%). This item also is found in a recent series of
12 cases of absent ductus venosus diagnosed prenatally
[29]. Some authors speculate
that the umbilical vein bypassing the liver may result in increased cardiac
preload, increased cardiac work, and progressive cardiac decompensation
[12]. An abnormal caval system
is now well known to be associated mainly with complex cardiac defects,
malrotation of the intestinal tract, and atrial isomerism
[14].
The biometric profile.—Of the nine cases with intrauterine growth retardation, a poor outcome was noticed in only two patients (22%) after exclusion of one syndrome with multiple malformations (case 11). Paradoxically, an increase of abdominal circumference might suggest hemodynamic distress (100%, severe in 5/7 cases) and requires immediate attention.
The associated anomalies (21/53 cases).— In six of 21 cases, the associated anomalies have modified the pregnancy course (termination or intrauterine death).
In conclusion, umbilicoportosystemic shunts are rare anomalies. In practice, one should recognize these vascular anomalies before hemodynamic distress or in case of unexplained hemodynamic changes. A sonographic examination, including a Doppler study, is useful to define the anatomic type of umbilicoportosystemic shunt, evaluate the outcome, and direct perinatal management.
Acknowledgments
We thank J. P. Lassau for providing
Figure 1.
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