Patent Urachus in Mule Foals: Urine Leaking From the Navel

Patent urachus is a condition in which the urachus, a tube that connects the fetal bladder to the umbilical cord before birth, stays open after delivery. In a healthy newborn foal, that tube should close soon after birth. When it does not, urine can leak from the navel instead of staying contained in the bladder and passing only through the urethra.

In mule foals, the condition is managed much like it is in horse foals because the anatomy and neonatal care principles are similar. You may notice a damp umbilicus, drops of urine at the navel, or a strong urine smell on the belly hair. Some foals otherwise seem bright and active at first, which can make the problem easy to miss.

Patent urachus can be congenital or can happen secondarily when inflammation, infection, or trauma affects the umbilical area. It matters because an open urachus can allow bacteria to move inward, raising concern for omphalitis, deeper umbilical infection, bladder involvement, or even neonatal sepsis.

This is not something to monitor for days at home without guidance. A prompt exam helps your vet decide whether the leakage is a mild isolated problem or part of a more serious umbilical or systemic illness.

The most direct cause is failure of the urachus to close normally after birth. This can happen as a congenital defect, meaning the structure remains open when it should seal off during the newborn period. In other foals, the urachus may reopen or fail to finish closing because of irritation or disease affecting the umbilical tissues.

Umbilical infection is an important trigger. Merck notes that patent urachus is the most common umbilical abnormality in neonatal foals, and some cases occur secondary to omphalitis. Infection can involve the external stump or deeper structures, including the urachus, umbilical arteries, or umbilical vein. When that happens, urine leakage may be only one part of the problem.

Birth-related trauma can also contribute. Difficult delivery, traction on the umbilical cord, or manipulation of the stump may interfere with normal closure. In neonatal foals, urinary tract trauma is also part of the differential diagnosis because tears of the urachus or bladder can cause urine leakage in or around the abdomen.

Mule foals may also face the same newborn risk factors seen in horse foals, including poor transfer of maternal antibodies, contamination of the umbilical stump, and concurrent neonatal illness. That is why your vet may look beyond the navel and assess the whole foal, not only the visible leakage.

Diagnosis starts with a hands-on newborn exam. Your vet will inspect the umbilicus, look for active urine leakage, feel for heat or swelling, and assess the foal’s temperature, hydration, nursing behavior, and overall strength. In straightforward cases, the visual finding of urine dripping from the umbilicus can strongly suggest patent urachus.

Umbilical ultrasonography is often the most useful test because it helps your vet evaluate the stump and deeper umbilical structures. It can show whether the urachus is enlarged, whether there is fluid or abscess formation, and whether the umbilical arteries or vein are abnormal. Merck also provides normal size references for equine neonatal umbilical structures, which helps clinicians judge whether infection is likely.

Your vet may also recommend bloodwork such as a CBC, fibrinogen, serum chemistry, or other neonatal screening tests if infection or sepsis is a concern. If the foal seems sick, cultures or additional testing may be needed. When abdominal distension, straining, or colic are present, your vet may expand the workup to rule out uroperitoneum, which is urine leakage into the abdomen from a ruptured bladder or urachus.

Because treatment choices depend on whether the problem is isolated, infected, or associated with deeper urinary injury, early imaging can save time and help match care to the foal’s actual needs.

Not every case can be prevented, especially congenital ones, but good newborn umbilical care lowers the risk of secondary infection and complications. Keep the foaling area as clean and dry as possible, make sure the foal stands and nurses promptly, and have your vet assess any weak, premature, or high-risk newborn. Early colostrum intake matters because foals with poor passive transfer are more vulnerable to infection.

Handle the umbilical stump gently. Avoid pulling, cutting, or aggressively manipulating it unless your vet specifically instructs you to do so. If the cord does not separate normally, forceful handling can traumatize the area. Watch the stump during the first several days for moisture, enlargement, heat, pain, or discharge.

Routine observation is one of the best preventive tools. A normal stump should dry and shrink over time, not stay wet with urine. If you notice dribbling from the navel, a urine smell, or any swelling, contact your vet early. Fast attention may allow more conservative care before deeper infection develops.

For breeding farms, a written foal-monitoring plan helps. Recording nursing, urination, temperature, and umbilical appearance in the first 24 to 72 hours can make subtle problems easier to catch while they are still manageable.