I found this article from Idaho Equine Hospital very interesting.  (You might want to follow them on FB.  They are great at posting very interesting medical news on FB – with photos!)

Foaling usually goes fine… but it can be very stressful.  Knowledge is power.  I had never heard of this condition, so I thought I would pass it on to you all.  We love foals – and the best way to keep them healthy is to understand the symptoms!

2 Cases of Uroperitonuem in Foals. By Robin Knight DVM, DACVIM

We recently had 2 foals that we did surgery on to correct a ruptured urachus. The fact that we had 2 cases very close together made us think that it might be a good topic to discuss and raise awareness of.

Let’s begin with a little anatomy-the urachus is basically a tube that connects the foal’s bladder to the allantois (fluid sac that surrounds the unborn foal). It runs through the umbilical cord and allows the foal to expel urine. After birth this tube normally closes, but in some cases this tube can develop tears and begin to leak urine. Depending on where the tear occurs, urine can leak into the abdomen, into the subcutaneous tissues (under the skin), or both. If it leaks into the subcutaneous tissue, you will notice a rapidly developing and progressive swelling around the umbilical remnant (navel). It is important to get these foals evaluated immediately because the urine is very irritating to the tissue and if not addressed quickly, it can cause a large portion of tissue to slough off of their belly. Both of our foals developed uroperitoneum (urine within the abdominal cavity), so they did not have external swelling around their navel, but both had abdominal distention. Each of the two cases were a little different and bring up some important points about the underlying problems and possible etiologies (causes) of this condition. It is worth noting, that the clinical presentation, treatment, and underlying causes of a ruptured bladder in foals are nearly identical to a ruptured urachus, in fact, the two conditions can occur in the same foal as you will see in the second case. The only thing that is different is what is required at surgery to fix the problem so all of the information that we present here also applies to cases of ruptured bladder.

Our first case was a foal who came to us shortly after birth because of a meconium impaction. We were able to relieve the impaction with enemas, but unfortunately a few days later the foal became lame and we discovered that he had an infection in one of his growth plates. This infection likely came from bacteria that had been in his bloodstream-a condition called sepsis that we see somewhat commonly in foals. We treated the infection aggressively with antibiotics and he was making good progress until he was about 7 days old. He had seemed bright and was nursing in the morning, but by that afternoon he was more lethargic and we noticed that his belly looked just a little bit more bloated than it had been. We used ultrasound to diagnose that he had increased free fluid in his abdomen and collected a sample of this fluid for analysis. The hallmark of this disease is that the abdominal fluid will have a higher creatinine than the blood (at least 2X). This occurs because creatinine is a waste product that is cleared by the kidneys and excreted in the urine, so when urine is being leaked directly into the abdomen, the creatinine in that fluid will be quite high. We took the foal to surgery that evening and found that he had urine leaking from the Urachus. Dr Kevin Wahl removed the urachus and closed the resulting hole where it had connected to the bladder.

The second foal had fluid in her abdomen when she presented to us. She had been born approximately 2 weeks premature but had been doing well until she was about 6 days old. Her owners noticed that she was not nursing and that her abdomen was distended so they brought her into the clinic. Just like the other foal we found free fluid in her abdomen and upon sampling, we found that it had a high creatinine. At surgery we found that she had an abscessed area in her urachus that was leaking urine, as well as a small tear in the dorsal (top) aspect of her bladder. Dr Kevin Wahl performed the surgery, he was able to close the tear in the bladder as well as removing the urachus.

One of the biggest issues with ruptured urachus (and bladder) is how rapidly these foals deteriorate. One reason is because urine is typically high in potassium. When the urine spills into the abdomen, the potassium is absorbed through the lining of the abdomen and enters the bloodstream. High potassium can cause fatal abnormalities in the electrical activity in the heart (arrhythmia). We checked the electrolytes in both of these foals prior to taking them to surgery. We also drained some of the urine off of their abdomen and provided them with IV fluids to help correct their electrolyte abnormalities. This is a very important step with any of these cases because death from heart arrhythmias under anesthesia is a real concern with these foals.

Historically, ruptured bladders were thought to be due to trauma to the bladder that occurred during the foaling process, and it probably is one of the causes of them. Likewise, with a ruptured urachus, trauma can be a cause-such as excessive strain on the umbilical cord (that is why we recommend letting it break on its own and not trying to pull or tear it). However, some more recent studies show that there are probably other contributors to these issues. A study published in 2005 looked at several cases of both ruptured bladder and ruptured urachus, they found that when they looked at the areas of tissue that had ruptured under a microscope, 46% of these areas had evidence of infection, and they were able to culture bacteria out of 9/15 of the samples. These findings suggest that sepsis (bacteria in the bloodstream of the foal) is likely a significant cause in many of the cases that we see. This makes a lot of sense from what we see clinically, as many of our cases are foals that are already hospitalized and being treated for sepsis and other issues.

Both of these foals had known risk factors for rupture of the urinary tract. Prematurity as well as meconium impactions (presumably because of increased straining by the foal) have both been implicated in increasing the risk of rupture. Other risk factors that have been discussed include dystocia (difficulty birthing) and delivery by cesarean section. Some early papers found an increased incidence in colts vs fillies, but this has not been a consistent finding in other papers.

Both of these foals displayed abdominal distention which is a very important sign of the disease. Other clinical signs can include not nursing, lethargy, colic signs, fever, and even neurological signs. Some foals will present with straining to urinate or decreased urination, but it is very important to note that foals with a ruptured bladder or urachus MAY still be able to urinate some. So seeing your foal pass urine does not rule out a rupture!!

Both of these foals showed abdominal distention around 1 week of age, and this is a very typical age for these foals to present, although we have seen it in both older and younger foals. We rarely see it over 1 month of age.

We are delighted to report that both of these foals are doing well and have been discharged from the hospital. We would like to thank Dave Merritt and Jeff Metcalf for allowing us to share these cases and to care for their wonderful foals.