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Obstetrics & Gynecology 2000;95:433-436
© 2000 by The American College of Obstetricians and Gynecologists
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ORIGINAL RESEARCH

Persistent Intrahepatic Right Umbilical Vein in the Fetus: A Benign Anatomic Variant

SHRAGA BLAZER, MD, ETAN Z. ZIMMER, MD and MOSHE BRONSHTEIN, MD

From the Departments of Neonatology and Obstetrics and Gynecology, Rambam Medical Center, Faculty of Medicine, Technion—Israel Institute of Technology, Haifa, Israel.

Address reprint requests to: Shraga Blazer, MD Department of Neonatology Rambam Medical Center POB 9602 Haifa, 31096 Israel E-mail: blazer{at}rambam.health.gov.il


   Abstract
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Objective: To evaluate outcomes of fetuses with antepartum sonographic diagnoses of persistent intrahepatic right umbilical veins.

Methods: A detailed fetal sonographic examination was done in 30,240 consecutive pregnancies at 14–26 weeks’ gestation. High- and low-risk pregnancies were included and persistent right umbilical veins specifically were recorded.

Results: Sixty-nine fetuses had persistent intrahepatic right umbilical veins, of which 60 had no additional sonographic abnormalities, four had transient nuchal findings, and four had minor anomalies or anatomic variants. Only one of the 69 fetuses had a major anomaly (diaphragmatic hernia), and died after surgery. The remaining 68 fetuses were normal and healthy after birth.

Conclusion: Persistent intrahepatic right umbilical vein is a fetal anatomic variant that is not rare and usually associated with a favorable outcome.

The persistence of a right umbilical vein in the fetus has been considered an uncommon condition. Jeanty1 gathered only a dozen instances reported in the literature since 1826, and added six new cases.2–6 Associated anomalies were found in all published cases and in three of Jeanty’s own six patients, suggesting that persistent right umbilical vein might be an ominous prenatal finding. Following Jeanty’s report on ultrasonographic prenatal diagnosis of persistent right umbilical vein,1 further series7–9 indicated that it was not that rare. However, data on incidence of associated significant congenital malformations were inconsistent, ranging from 11–50%.1,7–9

The purpose of this study was to determine the frequency of prenatal sonographic detection of persistent intrahepatic right umbilical veins in our obstetric population, consisting mainly of low-risk pregnancies, and observe associated congenital malformations and subsequent neonatal outcomes.


   Materials and Methods
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We did extensive targeted ultrasonographic examinations in 30,240 consecutive pregnancies over 10 years (1990–1999); no woman was counted more than once (ie, serial scans were excluded). The study population consisted of private self-referred patients interested in early sonographic detection of anomalies, or women referred by their physicians. Extensive targeted ultrasonographic examination of almost every fetus is customary in our area. Examinations mainly were by transvaginal sonography at 14–16 weeks’ gestation (83% of fetuses in this study), and abdominal sonography at 18–26 weeks’ gestation (17%). Eighty-seven percent of women were at low risk for congenital anomalies, whereas 13% had increased risk for fetal malformations (due to drugs, medications, x-ray exposure, personal or family history of congenital malformations, consanguinity, advanced maternal age, etc). Fetuses were surveyed for umbilical vein anomalies using the same method at similar gestational ages, and examinations were done by the same sonologist. During the first 3 years, we used an ESI 1000 (Elscint Ltd., Haifa, Israel) with a 6.5-MHz vaginal transducer and 3.5- and 5-MHz abdominal probes. Since 1994, we have been using an ESI 3000 (Elscint Ltd., Haifa, Israel) with a 7.5-MHz annular array vaginal transducer and 3.5-and 5-MHz abdominal probes.

Common sonographic markers of persistent intrahepatic right umbilical vein were anastomosis of the umbilical vein with the right portal vein rather than with the left portal vein; intrahepatic portion of the umbilical vein imaged laterally to the gallbladder, instead of medial to it; and portal vein curving toward the stomach instead of parallel to it (Figure 1Go).



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  		Figure 1. A fetus at 16 weeks’ gestation. Transverse diagonal section of the abdomen shows the right umbilical vein (UV) with its posterior part curving toward the stomach (S). The gallbladder (GB) marked by an arrow is between the umbilical vein and stomach.

 
When a persistent right umbilical vein was detected, a careful anatomic survey was done to exclude other congenital malformations. Amniocentesis and chromosomal studies were done in all the fetuses with malformations. The outcome of each pregnancy was recorded and postnatal physical examination results were collected from the medical records. Long-term follow-up of infants was done at 1–3 years of age by telephone interview of patients or children’s pediatricians.


   Results
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Sonographic diagnoses of persistent intrahepatic right umbilical veins were made in 69 fetuses, an incidence of 1 in 438, all in low-risk pregnancies. Eighty-seven percent were detected at 14–16 weeks’ gestation. In 60 of 69 (87%), persistent intrahepatic right umbilical veins were isolated findings with no other malformations pre- or postnatally, or on long-term follow-up.

Among the other nine fetuses, (Table 1Go) six had transient sonographic anomalies that disappeared later in pregnancy, one had a congenital diaphragmatic hernia, one had a double urinary collecting system, an anatomic variant, and one had a single umbilical artery. Karyotyping showed normal chromosomal analyses in all nine fetuses. The fetus with diaphragmatic hernia was delivered at 36 weeks’ gestation and died immediately after a surgical attempt to correct it. The remaining 68 newborns were normal after delivery, and remained so at follow-up.


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  		Table 1. Sonographic Findings Associated With Persistent Right Umbilical Vein
 
We found three fetuses with situs inversus in whom single umbilical veins were on the right side. However, because of the situs inversus condition, we could not establish whether they had true persistent right umbilical vein or a normal left umbilical vein that was abnormally located like all other viscera in situs inversus. The three had associated anomalies on ultrasound, one had scoliosis, spina bifida, and Chiari malformation type II, and one had corrected transposition of great arteries and pulmonary artery hypoplasia. Both were terminated. The third had asplenia and interruption of inferior vena cava; he is now 3 years old and developing well.


   Discussion
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At about the mid-fourth week of gestation, the sinus venosus, which eventually contributes to formation of the atrium, is a small transverse portion and right and left horns. Each horn receives blood from three sets of important veins, the common cardinal veins, from the fusion of the superior cardinal vein (which drains the upper part of the body) and the inferior cardinal vein (which drains the lower part of the body); the vitelline or omphalomesenteric veins, which drain the yolk sac; and the umbilical vein, which carries oxygen-rich blood from the placenta.10

During the sixth gestational week, the hepatic bud enlarges, while the right umbilical vein and the portion of the left umbilical vein between the liver and the sinus venosus degenerate, leaving only a left umbilical vein to carry all the blood from placenta to fetus. The ductus venosus forms in the liver and connects the left umbilical vein and the inferior vena cava. The ductus enables blood to bypass the liver and flow from the placenta to the heart. Postnatally, the left umbilical vein becomes the ligamentum teres.

Alterations of normal anatomy result from failure of the right umbilical vein to become obliterated and involute. A persisting patent right umbilical vein might coexist with the left umbilical vein as an intrahepatic supernumerary structure, or it might connect to the right portal vein. The intrahepatic right umbilical vein also might completely replace the left umbilical vein, which then regresses. The right umbilical vein might further persist and bypass the liver, causing an aberrant drainage of blood into the inferior vena cava or right atrium.1,7,9 The precise causes of failure of normal regression of the right umbilical vein are unknown, but several potential etiologies have been proposed. Obstruction of the left umbilical artery by thrombus, embolus, or external pressure early in pregnancy might cause the right umbilical vein to remain patent to maintain placental blood supply to the fetus.6 Specific teratogens and maternal folic acid deficiency in the first trimester also have been considered to increase risk of persistent right umbilical vein in a rat model.11

Alteration in umbilical venous anatomy was hitherto considered rare, particularly persistent right umbilical vein.1 Earlier reports were based on incidental pathologic findings from autopsies, detection during surgery, or upon insertion of umbilical vein catheters. Presently, prenatal sonographic detection is the main method of diagnosing persistent right umbilical vein. That widespread technique enables us to determine the true frequency of the condition, and shows that it is more frequent than reported. The incidence of 1:438 in our series was similar to the incidence of 1:476 reported by Hill et al,8 or 1:450 reported by Shen et al,9 and was lower than the rate of 1:250 reported by others.7 The true incidence of persistent right umbilical vein might be even higher, considering the false-negative rate of sonographic detection. The intrahepatic form of persistent right umbilical vein might present as an isolated finding, with no additional anomalies, whereas all the cases of persistent extrahepatic right umbilical vein were associated with significant fetal abnormalities (Table 2Go).7


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  		Table 2. Reported Series of Persistent Right Umbilical Vein
 
Our sonographic findings indicated severe malformations in 1.4% of cases with persistent intrahepatic right umbilical veins, compared with up to 50% of cases in the literature (Table 2Go). Our study was not a population-based study; therefore, bias was possible in incidence of associated anomalies. However, all our cases were detected in low-risk pregnancies. Despite the suggested association of persistent right umbilical veins with increased frequency of severe malformations and "transient" fetal anomalies (such as increased nuchal translucency), only one report of chromosomal abnormality could be found.12 Further studies are needed to clarify the relationship of persistent right umbilical vein and chromosomal defects, or to deem it purely coincidental. Karyotype analysis still might be indicated, especially when persistent right umbilical vein is accompanied by other sonographic anomalies. Reported cases of persistent right umbilical vein show a variety of cardiovascular, gastrointestinal, urinary, musculoskeletal, and central nervous system malformations. A summary of the literature (Table 2Go) showed that single umbilical artery was the most consistent finding. Two reported cases3,13 had situs inversus, as in three of our fetuses. It is unclear whether those cases represent genuine persistent right umbilical vein, or feature a normal "left" umbilical vein on the right side of the fetus, due to organ inversion. All those fetuses had malformations. Lai17 reported two cases referred for persistent right umbilical vein on obstetric ultrasonography examination. Careful fetal echocardiogram and Doppler examination showed an abnormal left umbilical vein in the setting of visceral situs inversus, with an interrupted inferior vena cava and azygous continuation.

Our data and those from other series indicate that persistent intrahepatic right umbilical vein is frequent. An extensive targeted ultrasonographic examination should be done whenever the condition is identified, and chromosomal studies are warranted in every fetus in which ultrasonographic abnormalities are detected. In the absence of associated malformations, a persistent intrahepatic right umbilical vein is usually an innocuous condition and carries a good prognosis.


   Footnotes
 
PII S0029-7844(99)00564-5

Received July 7, 1999. Received in revised form September 2, 1999. Accepted September 10, 1999.


   References
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Abstract
 Materials and Methods
 Results
 Discussion
 References
 
1. Jeanty P. Persistent right umbilical vein: An ominous prenatal finding? Radiology 1990;177:735–8.[Abstract/Free Full Text]

2. Leonidas JC, Fellows RA. Congenital absence of ductus venosus with direct connection between the umbilical vein and the distal inferior vena cava. Am J Roentgenol 1976;126:892–5.[Abstract]

3. Theander G, Karlsson S. Persistent right umbilical vein. Acta Radiol 1978;19:268–74.

4. Fliegel CP, Nars PW. Aberrant umbilical vein. Pediatr Radiol 1984;14:55–6.[Medline]

5. Bell AD, Gerlis LM, Variend S. Persistent right umbilical vein—Case report and review of literature. Int J Cardiol 1986;10:167–76.[Medline]

6. Ricklan DE, Collett TA, Lyness SK. Umbilical vein variations: Review of the literature and a case report of persistent right umbilical vein. Teratology 1988;37:95–100.[Medline]

7. Kirsch CFE, Feldstein VA, Goldstein RB, Filly RA. Persistent intrahepatic right umbilical vein: A prenatal sonographic series without significant anomalies. J Ultrasound Med 1996;15:371–4.[Abstract]

8. Hill LM, Mills A, Peterson C, Boyles D. Persistent right umbilical vein: Sonographic detection and subsequent neonatal outcome. Obstet Gynecol 1994;84:923–5.[Abstract/Free Full Text]

9. Shen O, Tadmor OP, Yagel S. Prenatal diagnosis of persistent right umbilical vein. Ultrasound Obstet Gynecol 1996;8:31–3.[Medline]

10. Sadler TW. Cardiovascular system. In: Sadler TW, ed. Langman’s medical embryology. 7th ed. Baltimore, Maryland: Williams & Wilkins, 1995:183–231.

11. Monie IW. Umbilical vein entering the right atrium: Comments on a previously reported human case. Teratology 1971;4:461–3.[Medline]

12. De Catte L, Osmanagaoglu K, De Schrijver I. Persistent right umbilical vein in trisomy 18: Sonographic observation. J Ultrasound Med 1998;17:775–9.[Medline]

13. Shryock EH, Janzen J, Barnard MC. Report of a newborn human presenting sympus dipus, anomalous umbilical vein, transposition of the viscera and other anomalies. Anat Rec 1942;82:347–60.

14. Ariyuki Y, Hata T, Manabe A, Hata K, Kitao M. Antenatal diagnosis of persistent right umbilical vein. J Clin Ultrasound 1995;23:324–6.[Medline]

15. Moore L, Toi A, Chitayat D. Abnormalities of the intra–abdominal fetal umbilical vein: Report of four cases and a review of the literature. Ultrasound Obstet Gynecol 1996;7:21–5.[Medline]

16. Chiappa E, Viora E, Botta G, Abbruzzese PA, Ciriotti G, Campogrande M. Arteriovenous fistulas of the placenta in a singleton fetus with large atrial septal defect and anomalous connection of the umbilical veins. Ultrasound Obstet Gynecol 1998;12:132–5.[Medline]

17. Lai WW. Prenatal diagnosis of abnormal persistence of the right or left umbilical vein: Report of 4 cases and literature review. J Am Soc Echocardiogr 1998;11:905–9.[Medline]




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