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PATENT URACHUS IN FOALS
Overview
The urachus is the tube within the umbilical cord through which urine from the unborn foal travels from its bladder to the allantois (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. When the urachus does not close, or closes and re-opens at a later date, urine continues to leak from the umbilicus. This is considered a persistent or patent urachus. The degree of patency varies considerably, ranging from that which allows an occasional drip and a moist navel, to full streams of urine.
Figure 1. Urination from both the penis and the navel in a foal with a patent urachus.
Causes
Failure of the urachus to close at the time of birth is termed a persistent urachus. 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 appeared to have sealed at birth. This type of patent urachus is most commonly associated with a navel infection causing disruption of the urachal seal and allowing urine leakage. However, it can also be caused by the foal straining (e.g. in the case of constipation) or by lifting the foal under the abdomen.
Signs and Symptoms
Foals with a patent urachus drain urine from the navel when they urinate and have moisture around the navel. Urine may leak from the navel from birth (persistent urachus) or urine leakage may begin within the first few weeks of life (patent urachus). Foals with a patent urachus may have a navel infection as well. 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 fever, depression, loss of appetite, and signs of serious systemic illness such as respiratory difficulty, lameness and swollen joints.
Figure 2. Foal with an infected navel. Notice the thickening of the navel, pus discharge from the end of the navel and wetness of the surrounding hair associated with a patent urachus.
Risk Factors
Debilitated and systemically ill foals are most at risk for developing a patent urachus.
When to Seek Veterinary Advice
Attention of a veterinarian should be sought as soon as urine is observed leaking from the navel. A patent urachus may serve as a source of systemic infection and should be corrected as quickly as possible. In the majority of cases of persistent urachus, closure can be achieved by your veterinarian without the need for surgery. However, these foals are susceptible to infection and your veterinarian can prescribe antibiotics to help prevent this.
If your foal has a patent urachus and/or a navel infection seek veterinary attention as soon as possible. Navel infections can become life threatening if the infection is allowed to spread through the bloodstream.
Examination
Your veterinarian will do a thorough examination of the foal to check for signs of systemic infection and confirm the presence of a normal urethra. He or she 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 patency between the bladder and the urachus, and help determine the presence and extent of infection and the structures involved. Blood assessment may be performed to help rule out infection, but if infection is present, bacterial cultures of the navel may be performed to determine which bacteria is causing the infection to help decide on the appropriate antibiotic for the foal.
Complications Caused by a Patent Urachus
Mild complications of a patent urachus include urine scalding of the abdominal skin surrounding the navel, dermatitis (inflammation of the skin) and local abscess formation. A more serious complication of a patent urachus stems from the fact that a patent urachus provides an environment favorable for bacterial infection. This infection can spread through the bloodstream and can lead to life threatening complications such as joint infection, pneumonia and generalized septicemia. Advanced infection of the urachus or navel and involvement of other body systems greatly decreases the chance of survival. Other less common complications include bladder infection, bladder wall necrosis and abdominal adhesions.
Treatment Options
In all cases treatment decisions need to be made with your veterinarian or veterinary surgeon. All foals with a patent urachus should be placed on antibiotic therapy to reduce the chance of the spread of infection and a barrier cream is applied around the navel to decrease urine scalding. In the absence of infection, many cases of persistent urachus will close on their own. If they do not close, foals with a persistent patent urachus usually respond to the application of a chemical cauterizing agent over several days. However, if after 2-4 days of treatment the urachus has not closed over, or if ultrasound examination reveals abnormalities associated with the internal structure of the umbilicus, surgical therapy may be recommended.
Cases of acquired patent urachus associated with navel infection should not be treated with cauterizing agents due to increased risk of urachal tearing and abscess formation. Due to the possibility of life threatening complications if the infection spreads, antibiotic treatment is absolutely necessary and should be based on bacterial culture results. These cases often require surgery to remove the infected navel structures (thereby removing the source of further infection) and close the opening between the urachus and the bladder. This surgery requires general anesthesia and post-operative nursing care. However, all decisions regarding treatment need to be made with your veterinarian or veterinary surgeon.
Potential Complications Following Treatment
The most common complication of using cauterizing agents to close a persistent urachus is the development of inflammation around the navel. Foals need to be carefully restrained during treatment to prevent inadvertent application of the cauterizing agent to the surrounding skin. Spillage of the cauterizing substance into the prepuce of male foals is especially discomforting.
Risks involving general anesthesia and the surgery itself are present 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. Find an ACVS Veterinary Surgeon.
Aftercare
Following surgery, 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. The foal needs to remain in a clean stall with restricted activity for several weeks. Once the abdominal incision is healed, regular activity can resume.
Prognosis
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.
Prevention
It is impossible to prevent a foal being born with a persistent urachus. However, to help prevent the development of a patent urachus and navel infection, it is important to dip your foal’s navel with chlorhexidine or a dilute iodine solution at the time of birth and several times over the next 24 hours. It is important for your foal to receive adequate colostrum to ensure that it has the required immunity to help fight infection. A simple blood test can be performed on your foal by your veterinarian at 24 hours of age to ensure that it has adequate immunity. If it does not, plasma can be administered to the foal to help prevent the development of infection in the navel or any other part of the foal.
Closely monitoring your foal’s navel in the first few weeks of life for any signs of moisture, enlargement or urine leakage are important to ensuring an early diagnosis of a possible problem. Call your veterinarian at the first sign of trouble to institute early treatment and give your foal the best chance for a successful outcome.
—Aimie Doyle, DVM, MS
Diplomate ACVS
Posted 4/02/2005
Updated 6/16/2008 by Dr. Doyle
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