The development of hydrops fetalis in the ovine fetus after lymphatic ligation or lymphatic excision.

Sixteen ovine fetuses underwent either ligation or excision of the left thoracic, left cervical, and left brachiocephalic lymphatic ducts. Our purpose was to test the hypothesis that interruption of lymphatic flow would lead to hydropic changes in the ovine fetus. Of the 11 animals in the group that underwent ligation, hydrops developed in 1. All five of the fetuses that underwent excision of these major lymphatic ducts were hydropic at the time of autopsy (3 to 7 days), with 62 to 502 ml of free fluid collected from the thoracic and abdominal cavities. The mean edema fluid total protein concentration in the hydropic fetuses was 2.6 gm/dl. This value was 71% to 94% of that found in the plasma, suggesting that the fetus is capable of producing new plasma proteins at a high rate. The observation that lymphatic excision led to hydropic changes in the ovine fetus, whereas ligation did not consistently produce hydrops, suggests that fetal lymph vessels may be capable of very rapid regrowth over short distances. Thus lymphatic excision, but not ligation, produces an animal model for the study of hydrops fetalis.