Fetal intra-abdominal umbilical vein varix: a case report

Introduction

The reported incidence of fetal intra-abdominal umbilical vein (FIUV) varix is very rare. The significance of this finding in pregnancy is still unknown. In a few cases, the prenatal diagnosis of this condition has been associated with poor pregnancy outcome such as fetal hydrops, fetal growth restriction and still birth.^1,2 However, in most isolated cases of fetal umbilical vein varix, the outcome is good. We report such a case.

Case report

A 31-year-old woman in her first pregnancy was referred to the antenatal clinic at 28 weeks of gestation by her community midwife as her uterus was measuring small for gestational age. The anomaly scan at 20 weeks was normal (Figure 1). OPEN IN VIEWER

An obstetric scan was performed to assess fetal growth and liquor volume. The growth was noted to be below the lower 10th centile, plotted on her customized growth chart. The liquor volume and umbilical Doppler wave velocity were normal. In addition, an intra-abdominal ovoid structure measuring 28 mm × 10 mm was seen superior to the fetal bladder (Figure 2). Color flow Doppler revealed venous flow in continuity with the umbilical vein (Figure 3). A diagnosis of umbilical varix was made. Venous flow was present throughout the lesion, suggesting the absence of thrombi. There was no evidence of fetal hydrops. Subsequent follow-up sonographic evaluations at 32, 34 and 36 weeks showed no increase in size of the umbilical varix. There was progressive fetal growth, although it remained below the lower 10th centile, with normal Doppler results and liquor volume. OPEN IN VIEWER

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Figure 3

Color flow Doppler showing venous flow in continuity with the umbilical vein

The woman was induced at 37 weeks of gestation for reduced fetal movements and had an emergency cesarean section for failed induction of labor. The procedure was uneventful and the baby was delivered in good condition. The baby was male with a birth weight of 2.6 kg. The Apgar scores were 9 at 1 minute and 10 at 5 minutes. Cord gases were within the normal range. Postnatal assessment and a follow-up cardiac echo scan on the baby were normal.

Discussion

By definition, an umbilical vein varix is a focal dilation of the umbilical vein. The diameter of the normal intra-abdominal umbilical vein increases linearly from 3 mm at 15 weeks gestation to 8 mm at term. ³ An FIUV varix is usually defined by an index portion of the umbilical vein that is at least 50% wider than the non-dilated portion, or dilatation to 9 mm or greater.^4,5 Other authors have defined the condition as a measurement that is two standard deviations above the mean for gestational age. ⁵

It is important to perform venous Doppler flow assessment, in order to differentiate this condition from other cystic lesions in the area, such as an urachal or choledocal cyst or a distended gallbladder, amongst others. ⁶ An umbilical varix is a developmental, rather than an embryologic abnormality. In most cases, ultrasonic features at 16–19 weeks gestation may be normal. ³ The frequency of diagnosis has greatly increased over the last 5 years, probably due to not only improved ultrasound technology, but also an increased awareness of the condition.

The significance of a prenatal diagnosis of umbilical varix remains controversial. Reported pregnancy outcomes from earlier case studies showed that a significantly higher proportion of pregnancies with this condition resulted in poor outcomes.^2,7 It has been linked to fetal growth restriction, hydrops fetalis and stillbirth. In some cases it has also been linked with chromosomal abnormalities.^2,4,7 The pitfall of the majority of the earlier studies is that cases of isolated umbilical varix were analyzed together with those associated with other structural abnormalities. New evidence from recent case studies shows that the majority of isolated fetal umbilical varix have a good outcome. However, the low numbers used in these studies (ranging from 28 cases to 10) make it difficult to draw definitive conclusions.^2,4,8–10

There is lack of consensus on the management of pregnancies complicated by fetal umbilical vein varix. Some have suggested that serial sonographic evaluation of the fetus, with particular attention to the blood flow within the varix should be carried out from diagnosis to delivery. In addition, the finding of this condition should prompt the search for other anomalies, with fetal karyotyping being offered only when other fetal anomalies are present.^4,9 Evidence is also lacking on the timing and mode of delivery of such cases. Studies have suggested that induction of labor should be considered at 36–37 weeks of gestation, based on the balance between concerns over reported poor outcomes in previous cases, against overall good outcomes in recent studies. ⁴ Other studies have not found sufficient evidence to suggest early induction of labor when fetal workup and surveillance is normal. However, caution is advised due to the previous reports of poor outcomes. ⁸ Early induction should be considered if there are signs of fetal compromise. ⁵

Conclusion

Our case supports the new emerging evidence that pregnancy outcome in cases of isolated fetal umbilical vein varix is generally good. Caution must be exercised against unnecessary early induction and costly preterm births.