I had been out of vet school just seven months. I was working in a general practice in northern New Hampshire that had hired me right out of vet school. It was a busy practice, and in those several months I had seen a fair number of horses. I was just barely getting over being totally anxious every time I drove onto a farm. When the phone rang that morning, it was a client who sounded even more nervous than me. There had been a winter storm the night before. In the bright morning light, she saw where her gelding had urinated on the snow. What startled her was the fact that the snow was colored red. She assumed that there was blood in his urine, and to be truthful, I bought right into it.
I went to her farm that day and agreed that the color of the urine soaked snow was a little alarming. The horse himself was bright and alert, feeling just fine. I did all the diagnostic things that I had been trained to do. I took blood. I poked. I prodded. His temperature, pulse and respiration were all normal. I tranquilized him, examined his penis, and even did a rectal to see how the bladder felt. His urinary system from bladder all the way up to his left kidney was perfectly normal. There was no straining.
That winter I ran into the same situation once or twice more. Each time it was right after a fresh snow. I finally realized that in each case the caller was either a new horse owner or one who had moved to the area from the south. I should tell you that, I wasn’t brought up with horses, and that this red colored snow was not something that I had learned about in vet school. Every winter since, when it first snows, I get the “red snow calls.” We had our first snow of the season on December 26 of this year. It took just 24 hours before I got the call. The owner had moved her horse home from a boarding barn. That meant that she was really caring for him for the first time. I asked if the horse was feeling OK, and she said that he was. I told her that, almost for sure, there was no need for a farm call. I let her know that she was the first caller of this winter season with the concern, and that I anticipated a few more before March. If you were brought up with horses in snow country, you have probably seen the deep orange to red stains on the snow from time to time after your horse has urinated. However, if you have never had your horses in snow, it is a surprise the first time you see it, and it looks alarming. What’s it all about, anyway?
The medical term for blood in the urine is hematuria. Pure blood or blood clots in the urine are not normal, and there can be a number of reasons. Horses can get bladder stones, and when these pass the lining of the urethra may get abraded and bleed. Inflammation and cancer anywhere in the urinary system may also cause bloody urine. These bleeding issues are almost always accompanied by other symptoms such as pain or straining. When quantities of blood are passed you will actually see blood clots in the urine. Horses that have tied up will pass very dark urine which results from the breakdown of muscle. There is also a rare and peculiar bleeding syndrome seen in Quarter horse males in which the lining of the urethra gets torn as it turns around an arch of the pelvis. All of these problems cause very real bleeding and are, of course, of concern and require veterinary attention.
However, the huge majority of cases of deep orange to red coloration on the white snow are usually the result of the uniqueness of the equine urinary system and not due to blood at all. Horses from time to time will normally pass mucus and minerals in the urine. This will thicken and darken the fluid. Horses also occasionally normally pass red blood cells in the urine. A certain amount is considered normal.
There are also some proteins in the urine which oxidize when exposed to air, much the same way that a sliced apple quickly turns brown. We all know what yellow snow is, and why we tell kids it’s not for eating. With horses, sometimes it’s yellow, and at other times it can be a deep orange to red color. You don’t notice the dark color until it is against the white snow. In general, if your horse is feeling fine in every other way, you can generally assume that the dark stained snow is just another demonstration of how special horses are.
On December 28 I got my second call.
–David A. Jefferson, DVM