The condition known as patent urachus occurs when the tube leading from the bladder of the unborn foal to the fluid-filled sac surrounding it does not close properly at birth, causing leakage of urine from the umbilicus of the young foal.
The degree of patency varies from an occasional drip to full streams of urine from the navel when the foal urinates.
The umbilical cord is a 20-40 inches cord that connects the placenta and the fetus. Its primary purpose is to serve as a conduit for the inflow of nutrients and outflow of waste products from the fetus. The structures in the umbilical cord are the two umbilical arteries and single umbilical vein and the urachus.
The urachus, a fetal canal, connects the bladder of the foal to the allantois of the placenta. At, or not long after birth, the umbilical cord ruptures spontaneously as a result of the movement of the foal or mare and the structures within normally seal off. The point of rupture is a place approximately ¼ inch from the foal’s body.
Obviously, inadequate closure of any of these structures creates the potential for bacteria from the external environment to enter the foal causing a hematogenous (blood derived) infection and for urine to leak from the urachus. Because of this, it has become a common practice to dip the navel and cleanse the area with a chlorhexidine solution in hopes of warding off potential problems.
Despite diligent disinfection and because many foalings occur unsupervised, it is not uncommon for foals to develop problems with their umbilicus. This is usually seen one to ten days after birth. A patent urachus occurs more commonly in foals that strain to defecate because of meconium impactions or with premature umbilical cord separation.
Unless the infection that causes the condition is treated, it may spread through the bloodstream, causing fever, respiratory difficulty, lameness, and swollen joints.
Debilitated or ill foals are at risk for developing this condition. Since patent urachus may serve as a source of systemic infection, a veterinarian needs to be called in to diagnose the problem and correct it as soon as possible.
Closely monitoring a foal's navel during the first few weeks of life for signs of moisture, enlargement, or urine leakage is important to assure an early diagnosis.
A veterinarian will do a thorough examination, including an ultrasound of the foal's navel to confirm patency between the bladder and the urachus. Blood tests will help determine the extent of infection, and bacterial cultures of the navel will help the veterinarian decide on appropriate antibiotic therapy for the foal.
In addition to antibiotic therapy, the veterinarian should determine whether chemical cauterizing or surgical means to close the urachus will work best to correct the condition.
Surgery to remove the infected navel structures may be necessary, and closing the opening between the urachus and the bladder will be done under general anesthesia. In some cases, the veterinarian may decide to cauterize the congenital patent urachus. In most cases, the foal will need to be removed to an animal hospital.
Following surgery or cauterization, the foal will need to remain at rest for several days with antibiotic treatments continuing until all danger of infection has passed. Restricted activity for several weeks in a clean stall will help with the healing process. .
Mild complications, such as urine scalding and dermatitis, that result from patent urachus should also be treated under the guidance of a veterinarian.