Fetal neck anomaly Distended jugular lymphatic sacs 2022-01-31T14:14:12Z The jugular lymphatic sacs (JLS) are a physiological and temporary part of fetal lymphatic development. They are formed from small buds of lymphatic endothelial cells arising from the internal jugular veins. By 14 weeks gestation they have developed into lymphatic nodes which drain into the systemic circulation. Visibility of JLS on ultrasound past 14 weeks of gestation implies distension and this may be associated with raised nuchal translucency. Distended jugular lymphatic sacs (JLS) may pre-date or accompany raised nuchal translucency or cystic hygroma and are associated with the same range of disorders. These are largely chromosomal aneuploidies or significant copy number variation. Current evidence suggests distended JLS in the absence of raised nuchal translucency are likely to be normal variation.