The "Big Picture"

In vet school there is always at least one class that you just don’t seem to comprehend, no matter how hard you study, or talk through it with classmates or stare at the pages of the textbook.  For me, one of those classes (there were actually a couple for me…) was pathology. Pathology is by definition the “condition and processes of disease.” 

We started learning pathology 2^nd year  of vet school at the cellular level and spent A LOT of time (6-8 hrs/wk) looking through a microscope.  It didn’t matter how much time I spent looking at slides or reading descriptions, it just didn’t make sense to me. I’m a “big picture” person. And looking at individual cells under 100 x magnifications was NOT big picture. I hated the class and thought I was going to DREAD my pathology rotation my senior year.

It wasn’t until that senior year rotation, where I spent 6 weeks on the necropsy (a.k.a. autopsy) floor, did the “big picture” finally make sense.  I’m not sure how many animals I actually necropsied, but examining the dead animal as a whole and then dissecting down to a microscopic level actually helped me figure out all the stuff I was SUPPOSE to learn 2^nd year…. By the end of the 6 weeks, I actually liked necropsies and trying to figure out why the animal died.

In general practice, I have performed multiple necropsies, but not nearly as many as I did during my pathology rotation at school.  Unfortunately, many producers don’t want to spend the money to figure out why the animal died, especially if it’s just one animal every now and then.  I will say that producers are MUCH more willing to spend the money when there are multiple deaths and there is obviously a serious disease wreaking havoc on the system.

 

I was at a regular herd check the other day when I saw a dead cow lying outside one of the pens.  As I always do, I asked the herdsman what the cow’s history was and if they knew why she died. In this case, the herdsman said they really didn’t know. She was a “low cow” which is a cow that is probably at one of the least stressful time periods of her life, other than a dry cow.  The night crew had said they found her pushed by the alley scraper to the edge of the pit where the manure dumps into.  Even if she slipped and fell, getting pushed by the alley scraper is not nearly enough to kill a cow.  So, I asked if they would like me to perform a necropsy on her.  They agreed that would be a good idea since there really was no other apparent reason for her death.

I’ve talked a bit about how we perform necropsies in at least one other post.  So as a quick review, we want the animal lying down on her left side so the right side is facing up. This is because the rumen takes up the entire left side of the abdomen and if the cow were laying on her right side, we would open the cow up and only see rumen.  We would then have to try to move the very large, very heavy, 2^nd stomach compartment out of the way to see the rest of the abdominal contents. 

Cows eye socket with white conjunctiva

Once the cow is lying on the correct side, I like to take an overall assessment of the animal to see if there are any obvious exterior signs the animal has. In this case the cow did not have any apparent scrapes, bruising, broken bones or discharge coming out of any orifice. I then noticed her eyes.  As you can see in the picture, the area around the actual eyeball is VERY white. So, before I even cut her open to evaluate the inside, I knew this cow had severe blood loss and cause of death was most likely due from exsanguination. I just had to find where such an event occurred. 

Findings when opening the abdominal cavity

When I opened her up, I found what is pictured.  The intestines all looked fine, but the blood obviously pooled in the cranial (front) part of the abdominal cavity. At first I thought this was a cow that suffered from a right displaced abomasum. When severe enough and twisted, a RDA can cut off all circulation to the intestines, essentially making them die off and turn black.  After a bit more investigation, I found the abomasum, and it was normal. This was NOT an RDA. 

 

I was then concerned that the cow may have suffered from hardware disease and the blood loss was from a punctured vessel caused by a wire or nail or some sharp metal object. Based on other findings such as perfectly normal lungs, heart and liver,  and lack of finding any sharp metal object, this was also ruled out.  When I cut into the blood mass, I thought I would be cutting directly into the stomach.  To my surprise, I cut into a giant blood clot and that was it. There was no feed material or fecal material coming out at me.  It was pure blood.  Dissecting further I realized that ALL of the blood was in the omentum, and all the stomach compartments and intestines were completely normal in appearance.

Blood Clot

Blood clot

The omentum is the “sling” that holds all of the abdominal contents in place.  It is a vital organ in that it will wall off any leakage from the intestines or infection, provides immune function and stores fat.  In this cow, I was able to dissect away enough blood in the omentum to follow the clot back up to the liver.  In the picture you can see the size of the vessel at the end of my thumb. It is not as large as the mammary veins are, however this is still a significantly sized vessel.

The vessel seen at the end of my thumb

Unfortunately there was too much blood for me to truly find whether there was an aneurysm or hole in the vessel. I did dissect through various parts of the liver to see if there were any liver abscesses that might have caused bacterial migration through the vessel and essentially erode the vessel so that it leaked.  The liver looked completely normal and healthy.

This is a diagram of the mesentery of a dog. Although a cow's is a little different, you can still appreciate how intricate and important the mesentery is and how many vessels could potentially have problems!

My diagnosis based on my gross findings or the “big picture” findings, was that the cow had a mesenteric artery or vein tear and bled out into the omentum. I don’t believe it was anything the farmer or herdsman was going to prevent and it wasn’t anything that would affect the rest of the animals in the group.  The omentum did its job and walled off the emergency, but unfortunately it was unable to stop the bleeding before the cow bled to death.  I may not know the exact microscopic pathology and the owner did not want to spend money to send in samples, but sometimes all we really need to see is the big picture.  In this case the “big picture” cause of death was from exsanguination.