The urachus is the tube within the umbilical cord through which urine from the unborn foal travels from the bladder to the allantoids (a fluid filled sac surrounding the unborn foal). Normally, the urachus closes at the time of birth and the navel dries and shrivels up within hours of birth. When the urachus does not close (persistent urachus), or closes and re-opens at a later date (patent urachus), urine continues to leak from the umbilicus. The amount of leaking urine varies considerably, ranging an occasional drip and a moist navel, to full streams of urine.
It has been suggested that partial twisting of the umbilical cord in the womb, or a greater than average length of umbilicus, may lead to dilation of the urachal tube and subsequent failure to close at birth. A patent urachus can also be acquired within the first few weeks of life, even after the urachus originally appeared to have sealed at birth, especially in foals that spend longer than usual periods laying down, therefore debilitated and systemically ill foals are most at risk for developing a patent urachus. This type of patent urachus is most commonly associated with a navel infection.
Early signs of infection may include an enlarged navel that is painful to the touch and discharge of pus from the navel opening. Navel infections can easily spread through the bloodstream causing:
- loss of appetite
- signs of serious systemic illness such as:
- respiratory difficulty
- swollen joints
Patent urachus can also be caused by the foal straining (e.g. in the case of constipation) or by lifting the foal under the abdomen.
Call your primary care veterinarian to evaluate your foal if:
- urine is observed leaking from the navel
- you can see/feel moisture on or around the fur surrounding the navel
- enlargement of the naval
Your veterinarian will recommend a thorough examination of the foal to check for signs of systemic infection. They may perform an ultrasound examination of the foal’s navel or send you to a referral clinic to have this performed. The ultrasound examination will help confirm communication between the bladder and the urachus, and help determine the presence and extent of infection and the structures involved. Blood work may be performed to help rule out infection, but if infection is present, bacterial cultures of the navel and or blood clultures may be performed to determine which bacteria is causing the infection to help decide on the appropriate antibiotic choice for the foal.
After surgical removal, the foal will need to remain in the hospital for several days for antibiotic treatment and observation. The abdominal incision needs to be monitored daily to ensure no signs of infection are developing. Once the foal returns to the farm, they will need to remain in a clean stall with restricted activity for several weeks with controlled hand-walking thereafter. Once the abdominal incision is healed, regular activity/turnout can resume. The exact postoperative care recommendations with be provided to you by your veterinary surgeon at the time of discharge from the hospital.
- The prognosis for a persistent urachus is excellent in most cases.
- The prognosis is good in cases of acquired patent urachus with associated navel infection when there is early diagnosis and prompt medical and surgical treatment.
- Advanced infection and spread of infection through the bloodstream greatly reduce the chance of survival and the prognosis is guarded.
There are inherent risks involving general anesthesia and surgery if surgical removal of the urachus and navel is necessary. Your veterinary surgeon will explain these risks in detail before performing surgery on your foal.