Distended fetal jugular lymphatic sacs in the first trimester of pregnancy

Abstract

A 31-year-old woman was referred at 13 + 2 weeks of gestation in her second pregnancy with increased nuchal translucency (NT) thickness of 2.9 mm for a crown–rump length (CRL) of 65 mm. NT measured at referral (GE Voluson 730, General Electric, Gif sur Yvette, France), which was 4 days after her initial scan, was 1.6 mm. In addition, two cystic cavities measuring 2.5 × 4.5 and 3.1 × 5.4 mm were visualized, in both sagittal and axial planes (Figures 1-4), one on each side of the fetal neck, which were recognized as distended jugular lymphatic sacs. The fetal karyotype was normal, as were follow-up ultrasound examinations at 22 and 32 weeks of gestation. Sagittal ultrasound view of the fetal neck showing thin nuchal translucency. Axial ultrasound view of the fetal neck. The distended jugular lymphatic vessels are seen as two round anechoic structures. Three-dimensional ultrasound imaging with minimal transparency mode, showing the coronal view of the fetal cervical area. Three-dimensional ultrasound imaging with the inversion mode, showing the fetal jugular lymphatic vessels and sacs. There has been an ongoing debate regarding the differentiation between increased NT and cystic hygroma in the first trimester of pregnancy1. Further uncertainty can arise from the recognition of isolated dilated jugular lymphatic sacs at 11–14 weeks' gestation with normal NT measurement, disappearing on follow-up examination. The significance of this finding is still poorly understood but it is likely to arise from physiological variations in the timing of lymphangiogenesis. The visualization of isolated mildly distended jugular lymphatic vessels or sacs on ultrasonography is therefore probably not sufficient to establish the diagnosis of cystic hygroma. Fetal cystic hygromas are congenital malformations of the lymphatic system of the neck. They are thought to arise from failure of the lymphatic system to communicate with the azygos vein at around 8 weeks of gestation and, as they get larger, can cause nuchal and generalized edema. Ultimately this can affect venous return to the heart and cause hydrops through the jugular-lymphatic-obstructive-sequence (JLOS)2. Sharony et al.3 reported an incidence of cysts in the fetal neck of 2.4%, of which 4.2% (confidence interval (CI), 3.6–9.5%) were associated with fetal aneuploidy. Bekker et al.4 reported a strong association between increased NT and dilatation of fetal jugular sacs on first-trimester ultrasound. The same team also showed that enlargement of the jugular lymphatic sacs preceded that of nuchal edema in a mouse model of trisomy 165. Irrespective of the transient nature of the findings in our case, caution should be taken in interpreting images obtained using advanced technology in the very sensitive area of the fetal neck.