Page 97 - August 2021

the abdomen—that it can’t be identified by palpation or trans-rectal ultrasound, but we can identify a large amount of fluid,” she says. Trans-abdominal ultrasound can confirm an excessive amount of fetal fluids.
Ultrasonography of the abdominal walls and prepubic tendon for evidence of edema
is necessary to monitor impending body wall tears, and prepubic tendon rupture, which commonly occurs with hydroallantois and can dramatically worsen the prognosis for survival and reproductive value of the mare.
TREATMENT
With mares that are evaluated and diag- nosed early at 5-7 months of gestation, the veterinarian may opt to terminate the preg- nancy. Later in gestation, or in mares with excessive abdominal enlargement and large volumes of fluid in the placenta, controlled drainage of the fluid is necessary before the fetus can be delivered. “Controlled, slow drainage is essential because a sudden altera- tion of total body fluid balance—with sud- den loss of this large volume of fluid—may result in hypovolemic shock and the mare can die,” she says.
“You do not want all that fluid to come out at once or to let the pregnancy go full term since this will be detrimental to the mare and foal. The other problem is that the weight and pressure of the excess fluid puts a lot of strain on the muscles of the abdominal wall. This can cause rupture of the prepubic tendon, which is the large tendon that supports the abdominal cavity. When this happens, the prognosis for the mare is worse,” says Wolfsdorf.
If a mare has great difficulty walking, she may prefer to remain lying down, especially with hydrops allantois.
“You want to identify the problem and
drain the fluid prior to rupture of the prepubic tendon or an abdominal wall tear,” she says. It
is an emergency because the excess fluid can appear suddenly, and the consequences occur equally suddenly. The veterinarian may advise supportive care that includes abdominal support (an abdominal band), IV fluids, broad-spectrum antimicrobials, and anti-inflammatory drugs.
Slow siphoning of the fluid can be accom- plished by using a tube inserted through the cervix and through the placenta with extension
tubing attached to control the flow rate, taking a couple of hours to drain. At the same time, intravenous fluids should be administered to maintain fluid/electrolyte balance in the mare and prevent shock. In many cases, the mare will be sedated for this procedure.
“I don’t drain all the fluid—just enough
to take away the pressure on the abdominal structures and the uterus and prevent shock. If you take too much fluid, even if you drain it slowly, the mare may still go into shock. There is a fine line between how much is enough and how much is too much,” says Wolfsdorf.
“When inserting the drain tube, we also need to be careful that we don’t damage
the cervix. Once enough fluid is drained, depending on the clinician, some will induce foaling to make sure someone is present
to assist delivery. Personally, I prefer to let mother nature take its course because I think this relaxes the cervix a little better than when we induce labor. You do have to realize that with the uterus having been so dis- tended, it has no tone or strength to contract appropriately and you will probably need
to assist in delivery of the foal.” The mare would have trouble pushing the foal out.
“Generally, the mare will be brought into the hospital for us to drain the fluid and treat the mare. I advise sending the mare to a refer- ral facility to have this done, so fluids can be administered at the same time as the drainage. If the mare is down and bringing her to a hos- pital is not an option, the veterinarian can try doing this on the farm, but if the condition is detected early, the mare should be able to travel to the hospital,” says Wolfsdorf.
EQUINE HEALTH
The main sign of Hydrops is that the mare’s abdomen becomes very large very quickly. The abdomen looks like an apple—very round—too large for that stage of pregnancy.
The veterinarian can diagnose hydrops allantois, and sometimes hydrops amnios, by palpating the mare.
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