Patent Urachus

Q. I have a 10-day-old orphaned foal. When she urinates, it also comes from her navel. I have talked to our vet, but would like to read more about this condition.

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A. Patent urachus is the term used to describe the condition of urine dripping from the navel. When the fetus is in the uterus, urinary waste is excreted (backwards, if you will) from the bladder out the umbilicus and into the large fluid sac, the allantois. In the fetus, the bladder is much longer and tubular and is called the urachus. Once the foal is born, the umbilicus breaks, and the two arteries and vein will clot and seal.

The urachus also seals. The part that attaches to the body wall atrophies, and the remaining structure becomes a round bladder. Dripping urine from the umbilicus indicates that there is an interruption in this process. The most common cause of urachal patency is infection. Most commonly, the infection is superficial and involves just the part of the urachus that attaches to the body wall. These infections can be self-limiting, but I prefer to treat with seven to 10 days of oral antibiotics as they resolve quickly.

Less commonly, a patent urachus can be an expression of infection deeper in the umbilical remnants (usually artery or vein) or of septicemia (blood-borne infection). For this reason, I prefer to perform an ultrasound examination of the umbilical remnants of all foals with patent urachuses. If the vascular structures are fine, and the urachus appears inflamed, these foals respond well to antibiotics. If there is an infected umbilical structure, I prescribe antibiotics first, and monitor the size and appearance of the umbilical structures with ultrasound. Most will resolve with antibiotics, but a very small percentage of these foals will ultimately require surgery to remove infective foci (areas). However, I prefer to reduce their size and the local inflammation with antibiotics first.

One note: I have seen patent urachuses be the result of either too frequent dipping of the umbilicus or using a caustic antiseptic like 7% iodine. Inflammation is the cause of the patency. For normal foals, dipping the umbilicus with a mild antiseptic a few times daily for the first couple of days is plenty.

About the Author

Elizabeth Santschi, DVM, Dipl. ACVS

Elizabeth M Santschi, DVM, Dipl. ACVS, is a professor of equine surgery at Kansas State University’s College of Veterinary Medicine, in Manhattan.

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