The umbilicus in the mammal is the structure that links the mother with the fetus during pregnancy. The structure is made up of four parts: an umbilical vein, two umbilical arteries and the urachus. The umbilical vein carries oxygen and nutrients from the mother's placenta to the fetus while the umbilical arteries carry carbon dioxide and other waste products from the fetus back to the dam again through the placenta. The urachus is a direct connection between the fetus's urinary bladder and the allantoic sac. The kidneys of the fetus begin functioning during the gestational period and this provides an exit for the urine that is produced.
The newborn foal may remain attached to her mother through the umbilical structures for a few minutes. If you were to place your hand on the umbilicus at this time you would feel a continued pulsation of the umbilical arteries. This is the flow of blood from the mare's placenta to the foal's bloodstream. Some people feel that it is important for the mare and foal to lie quietly for a period of time (1 to 5 minutes) to ensure that the foal receives all the blood it can through this placental transfusion. In contrast, others feel that blood exiting the foal through the umbilical vein is sufficient to counterbalance the benefits of placental transfusion.
The umbilical cord should rupture when the mare attempts to stand. The actual stretching of the umbilical cord will cause the walls of the arteries and veins to contract thus sealing them to prevent leakage of significant quantities of blood or hemorrhage from the foal. There is usually no need to place a suture on the umbilical cord, although occasionally a foal will have unusually large umbilical blood vessels, which continue to bleed after the mare has ruptured the cord. In this case, a sterile suture may be necessary to stop the bleeding.
The foal's umbilical stalk is what is left after separation from the mare, and it can vary in length – it may break off close to the abdominal wall or two to three inches long from the wall. At first it is about as big in diameter as an average person's thumb. Over the course of the first week of life this structure become shorter in length and smaller in diameter. Eventually it becomes a dried up piece of tissue that falls off the foal around 7 to 10 days after birth. Blood flow through the internal structures of the umbilicus stops at birth and these structures eventually turn into abdominal ligaments.
Umbilical infection, also known as navel ill or omphalophlebitis, is usually seen in foals from the age of 2 to 3 days up the age of one month. The infection most likely occurs at the time of birth or soon after. The raw umbilical stump is open to the possibility of infection because most foals are not born into a sterile or even clean environment. In fact, the mare sometimes defecates while in labor and the foal may be born on top of a fecal pile.
Umbilical contamination at birth or during the first week of life can lead to an ascending infection from bacteria in the environment. The infection may involve one of the structures such as an umbilical artery, or it may involve all of the umbilical structures resulting in abscess formation. Umbilical infections have been cited as one of the key points of entry for bacteria that cause septicemia, a widespread infection throughout the body. In one study of septic foals, 25 percent of the foals had an umbilical infection and fifty percent of the foals with septic arthritis had confirmed umbilical infections.
Foals with umbilical infections have a slightly different clinical profile depending on their age. Very young foals, 2 to 5 days old, are presented for another problem such as depression, septicemia or pneumonia. These foals often have a history of failure of passive transfer of colostral antibodies.
There is often no external evidence that a foal has an umbilical infection. Diagnosis of the problem is made with the use of ultrasonography. The ultrasound allows us to look at the internal structures of the umbilicus. Measurements of the diameter of the umbilical stalk, which contains both arteries, the vein, and the remnant of the urachus, and of the diameters of each individual structure can be made and compared to established normal values. If any of the measurements are larger than the enlarged structure, they should be considered infected.
In the older foal, an umbilical infection is more likely to be visible externally. The umbilical region of the abdominal wall is swollen, warm and painful and may drain pus. These foals often have a fever and an elevated white cell count.
The treatment goal is to eliminate the infection before it can spread to other parts of the body, such as the joints. In the young septic foal, the treatment is directed at the main problem of septicemia. This includes antibiotics, plasma transfusion, intravenous fluid support, nutrition, etc. The antibiotics may help in reducing the umbilical infection, but the blood flow to these structures is poor after birth thus high levels of antibiotics may not be able to clear the infection. Follow-up ultrasound examination are helpful in determining whether the infection is responding to treatment or getting worse.
In the older foals and in the medically stable younger foal, surgical removal of the umbilical structures is the preferred method of treatment. A midline incision is made through the abdominal wall, and the infected structures are dissected out and removed. Prognosis for recovery is good if the foal has not "seeded" the infection into other parts of his body.
Home Care and Prevention
Prevention of umbilical infections is directed at three different areas – ensuring the foal receives adequate colostrum, local disinfection of the umbilicus and environmental sanitation. Disinfection of the foal's umbilicus should take place as soon after birth as possible. Once the umbilical cord has broken, slip quietly into the stall, trying not to disturb the mare, and apply either a 0.5 percent chlorhexidine or 2 percent iodine solution to the umbilical stump. In the past tincture of iodine has been used, which is very strong. This can cause skin irritation around the umbilicus and is no longer recommended.
The easiest way to treat the umbilicus is to place your disinfectant in a clean glass jar about the size of a baby food jar. Place this jar over the umbilicus and press it against the body wall creating a seal and submerging the cord. This procedure can be repeated several times a day for the first 2 days.
Environmental cleanliness is important. Even though you can't ensure that the foal will not be born onto a fecal pile, you can keep the stall as clean as possible, not only at the time of birth but throughout the first week of life. By cutting down on the bacterial load in the environment, you will decrease the bacterial burden that the foal has to defend himself against.