Hydrops fetalis is defined as abnormal accumulation of serous fluid in the skin (edema) and body cavities (pericardial, pleural or ascitic effusions). Several hypotheses regarding the pathophysiologic events that lead to fetal hydrops have been suggested. The basic mechanism for the formation of fetal hydrops is an imbalance of interstitial fluid production and the lymphatic return.
Hydrops is a non-specific finding associated with a variety of causes, including cardiovascular anomalies, hematological disorders, chromosomal abnormalities and infection. Hydrops is divided into immune (due to maternal hemolytic antibodies) and non-immune (due to all other etiologies) types. In humans this condition occurs in 1 of 3000 pregnancies.
This paper describes the first case of hydrops fetalis reported in a dolphin. The hydrops was diagnosed by ultrasonography at three months gestation and monitored for the next two months.
The mother was a 15 year old Tursiops truncatus gilli, which had previously delivered a healthy calf in July 2004. One year and eight months later she became pregnant again and by the same male. At three months of gestation ultrasonography showed a live fetus with gross hydrops fetalis, with severe subcutaneous edema, mild abdominal ascites, hydrocephalus and the umbilical cord around a small, deformed tail. The placenta was thickened and echogenic. The biparietal diameter measured 4.5cm and the fetal length was about 26cm. The widest diameter of the fetus was at the level of the neck and was 13cm. We continued monitoring the fetal growth twice a week and estimated a growth rate of 1-2cm per week. Because of the steadily increasing diameter of the fetus and concerns about a potential dystocia, plans were made for an early delivery.
During ultrasonography on August 5, 2006, the fetal heart beat was seen to have slowed to 50 beats per minute. On August 7, 2006, it was not possible to demonstrate a fetal heart beat and at 12.35h on August 9, the dam aborted.
Necropsy showed a severely edematous, female fetus, measuring 34cm in length and weighing 1.650kg. The heart had a severe multifocal edema. The lungs where collapsed with some distended spaces. There was mild abdominal ascites. The adrenals were slightly edematous and the kidneys showed mild degeneration of the tubular epithelium. In the trachea, the submucosa was moderately expanded with edema. The liver was also edematous, showing degeneration with congestion and extramedullary haematopoiesis. The umbilical cord showed mild perivascular edema. The cranial cavity contained 46ml of fluid and the brain was macerated.
In the placenta, we found different grades of edema, congestion and occasional presence of fibrin material. We did not observe microscopic evidence of any disease or other abnormality.
The prenatal diagnosis of hydrops fetalis by ultrasonography at three months of gestation was confirmed at necropsy. We were not able to find a definitive cause of the hydrops, but suspect it may have been due to infection during early gestation. One month after the abortion, the female in this case became pregnant for the third time, by the same male. At the present time, no abnormalities have been observed on ultrasonographic examination.
The authors would like to thank all the staff of Dolphin Adventure for their work, also Dr. Leonardo Ibarra, Dr. Bill Van Bonn and Dr. Sam Dover for their help in this case.