Tuesday, March 8, 2011

Going the Distance - 
to a Happy Ending
     I think of it most commonly in murder mysteries.  You know, the Sherlock Holmes guy who recognizes the connection between several apparently unrelated events that no one else thinks are important and the next thing you know - voila! the murderer is exposed. This story is a bit like that.  It is about Spring, a 9 yo mare who has beaten the odds, thanks to an observant veterinarian and a dedicated owner.  
       Last summer  I was called out to see Spring twice because she had a severe dermatitis affecting the white part of her muzzle.  I treated her for photosensitization, a common problem in northern Nevada where horses with white skin fed alfalfa have a dramatic reaction to sunlight that results in a painful, sunburn like inflammation, seen most commonly on the nose and white areas of the lower legs.  In January Spring's owner called me because once again the white skin of Spring's nose was severely inflamed.  At this point I became concerned about an underlying problem.  A few things didn't make sense: 1) Spring's diet had been carefully managed to eliminate consumption of ingredients, such as alfalfa, that might contribute to photosensitization, and 2) it was January - the days were short and we had had lots of bad weather, meaning there wasn't enough sunshine to trigger a typical episode. I began to wonder about the health of Spring's liver.  
      The liver plays an important role in detoxifying phylloerythrins, the photodynamic substances that cause photosensitization.  Thus an unexplained episode of this problem may be an early sign of liver disease.  Consequently we began an extensive evaluation of Spring's liver, which included serial blood work, hepatic ultrasound and finally a percutaneous liver biopsy.  All the news was bad.
     Spring had persistent elevations in the active hepatocellular enzymes that indicate ongoing damage to liver cells.  Her biopsy showed extensive fibrosis, or scarring of the liver, indicating that the disease process had been going on for a prolonged period of time.  Ultrasound revealed that her liver was smaller than normal. There are several diseases that result in the findings observed in Spring.  The one that fit Spring's findings most closely  is called Chronic Active Hepatitis (CAH).  It is a poorly understood disease process, most likely immune-mediated. It carries a very poor prognosis for long term survival, and in general does not respond well to medical treatment.
     If you received our most recent e-news letter, you read my article on veterinary networking.  Spring's case is a wonderful example of how networking makes us all smarter.  I presented Spring's case to the American College of Veterinary Internal Medicine Specialists' list serve and asked for input from my colleagues.  Most agreed that a diagnosis of CAH was correct and treatment with steroids and anti-fibrosing agents should be attempted, but the outcome was not hopeful.  However, one of my colleagues and mentors from the University of Georgia where I completed my residency and PhD program, suggested another possibility.  Dr. Michelle Barton wondered about the possibility of a stone in the common bile duct, which would not be visible on ultrasound.  Although Spring's diagnostic findings did not fit this picture perfectly, Dr. Barton pointed out that this was the only disease she could have with any hope of treatment, and that the only way to rule it out would be an exploratory surgery, because in the horse the common bile duct can only be visualized and fully examined at surgery.
       Horses don't have gall bladders.  The liver makes bile, which is excreted through the common bile duct into the small intestine.  In order to access the bile duct, the horse is placed on its back under general anesthesia.  A large incision is made along the midline of the abdomen - the same incision made for colic surgery, but much longer, extending forward almost to the sternum.  The surgeon must lift much of the gastrointestinal organs out of the abdomen, then reach far down and forward into the abdominal cavity to find the bile duct as it exits the back of the liver along with the hepatic vein and artery.  It is a very difficult surgical exposure. 
    Now Spring's owner had to make a really tough decision. The odds of Spring having a bile duct obstruction that could be resolved at surgery were small.  The anesthesia and stress of surgery could precipitate a crisis and push Spring from a state of compensated liver disease into full blown liver failure which would almost certainly be fatal.  On the other hand, if Spring did have a bile stone that the surgeon could loosen up and move from the bile duct into the small intestine, Spring's prognosis for long term survival would improve markedly.  I spent a long time talking to Spring's owner, explaining the options, looking at things from various perspectives, talking about possible outcomes, and listening to her owner's thoughts and concerns about Spring's quality of life.  My recommendation was to go forward with surgery because it provided the only hope of a significant positive impact on the disease process progressing in Spring's liver.  
      The picture at the top of the page tells the story.  I took it during Spring's surgery, conducted by Dr. Shane Miller, a board certified equine surgeon. At surgery the liver was found to be small, with a markedly fibrotic right lobe.  Dr. Miller did not feel a discrete bile stone in the bile duct, but the duct was very firm on palpation, and Dr Miller massaged and manipulated the duct in hope of freeing any bile "sludge" that might be occluding the flow of bile through the duct.  At surgery we all were pretty disappointed, and thought that our best hopes of improving Spring's outcome had not been realized.
     After surgery everything began to change. Spring had no difficulty at all related to the surgical procedure.  She recovered uneventfully from anesthesia and had no problems with her large surgical incision.  Her liver enzymes were carefully monitored for 3 days post-operatively for signs of deterioration secondary to the stress of surgery.  Surprise surprise surprise.  The enzymes that indicate bile obstruction and active liver cell damage began to decrease immediately after surgery and continued to move toward normal numbers.  Four weeks after surgery Spring's blood work is normal!  Just like mud in a hose, the firm material that Dr. Miller felt on palpation of the bile duct was most likely stagnant, thickened bile "sludge" that he loosened up with his manipulation at surgery.
    Currently Spring is being maintained on a grass hay and beet pulp based diet, which is rich in branched chain amino acids, readily metabolized by the liver.  She also is receiving pentoxyphylline, a medication that acts to reduce fibrosis.  She looks great and can't wait for her incision to finish healing so that she can be turned out to pasture and then get back to work!
    Spring's story is far from over, but at this point I cannot thank all the people involved in the Spring network enough for their contributions to her diagnosis, treatment, and recovery.  First of all her wonderful owner, who listened, digested and formulated her decisions with only one thing in mind: her horse's well being.  And then to the team of veterinarians, especially Dr. Barton and Dr. Miller, who contributed their knowledge, experience and clinical expertise to Spring's case.  It truly does take a Village. 
I believe that education is the key to evolution. I believe that animals are the key to compassion. I believe the learning never stops.


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