Thursday, June 16, 2011

Nephrosplenic Entrapment

No, it is not a legal term. Nor is it an exotic food. Rather, it is a type of colic where the horse's left colon gets hooked over the ligament connecting the spleen and left kidney and causes the horse pain due to mesenteric pull and gas distention.

Yesterday a referral came in about a horse with a suspected colic. We didn't get much information besides that "Louie" was looking a little off, and a warning that he was kind of pushy. I was excited to see something medical rather than surgical, so I jumped in the car with Dr. Intern and we headed down the road.

Louie turned out to be a good sized paint horse, who did indeed look uncomfortable. We had his owner, an earnest teenage girl, lead him out of the relentless sun into a covered area for examination. Louie just appeared restless and painful, hanging his head while he shifted his weight and pawed the ground. His owner informed us that he had passed only a small volume of feces today (unusual for a horse, which is an eating machine, and therefore a pooping machine). Dr. I performed a physical, focusing in particular on his heart rate (a possible indication of pain) and his gastrointestinal sounds. I watched as she listened to his upper and lower abdomen on the right and left sides. Next, she did something that I had only encountered in the context of cattle: she "pinged" the horse on its upper left abdomen.

"Pinging" is the process of listening to the abdomen while flicking the area around the stethoscope with your fingers. If there is any gas trapped there, you will hear a high "ping," like the noise you make when you tap on an inflated basketball. Dr. I told me to have a listen to the abdomen. She told me there was one abnormality, but not what it was. I was quite proud when I identified that gas-filled upper left abdomen, especially since I never really understood what a ping sounded like in a cow. On top of this, Louie also had almost no GI sounds in the other quadrants of his abdomen, indicating that his gut was not moving.

Dr. I administered a dose of pain medication and a sedative, noting the time. The rate at which the pain breaks through the drugs, she explained to me, can be an indicator of the severity of the colic.

To get an idea of what we were working with, Dr. I donned a rectal sleeve and lubed it up. Standing carefully to the side of Louie's back legs, she performed a rectal exam. This confirmed a large, gas-filled structure on the left side, which she suspected was left colon.

Even though this colic was most likely a hindgut issue, she decided to attempt passing a nasogastric tube to reflux and stomach contents. Louie, however, was not up for that, and we gave up when it became clear that we did not have the manpower to hold even a sedated Louie still enough to shove a piece of plastic tubing into his nostril, down his choana, into his pharynx, down his throat (avoiding the trachea) and into his stomach. Louie's teenage owner and I were both nearly lifted off the ground trying to hold his head.

The decision was made to trailer Louie to the clinic; that way if Louie's abdomen turned surgical, we would waste no time, and even if it remained medical, we would be better equipped to support the gelding. Louie's pain seemed to be controlled for the time being, so we loaded him into a trailer and headed for the clinic. Some cases. Dr. I told me, actually will resolve themselves over the course of a trailer ride because of the motion of the vehicle. We crossed our fingers that Louie would be one of those lucky horses.

When he arrived at the clinic, Louie was becoming painful again. We hustled him into the stocks and gave him another dose of pain meds and sedation. The next step was an ultrasound of the abdomen, which confirmed the nephrosplenic entrapment that Dr. I had suspected. I admit that while I can recognize structures on tendon and musculoskeletal ultrasound with some facility, the abdomen looked completely unfamiliar to me. I gathered that not being able to see a distinct spleen and left kidney indicated that they were hidden behind gas-distended colon.

In the stocks, and with more hands restraining him, we were able to pass an NG tube on the second try. I stood on the left and held his ear, trying to convince him not to throw his head. At last we smelled stomach gas at our end of the tube, and Dr. I pumped clean water into his stomach, and then collected whatever came out. We refluxed a small amount of fluid and some gas. Clearly, this was not the source of Louie's pain.

The next step was to get intravenous fluids into Louie. It was a hot day, the horse was agitated and sweating, and since he had been feeling poorly, had not been drinking. To combat possible dehydration and electrolyte imbalance, we placed a catheter and began to bolus plasmalyte once Louie was safely in a stall.

Dr. I decided to administer a peripheral vasodilator in the hopes that it would shrink Louie's spleen and allow the loops of colon to slip off and back into their normal orientation. Since this drug causes peripheral vasodilation, a concomitant increase in the volume of blood in the heart occurs. This increase is sensed by baroreceptors in the great vessels, and sets off a decrease in heart rate. Obviously, a heart rate that drops too low can result in syncope, or fainting, and with a 1500 pound horse, this is a big problem, both for the horse and for any hapless humans in the area. As a result, I was given the job of monitoring his heart rate during the twenty minutes over which the dose was administered. This may have been the best part of the whole experience, because now I have no doubt that I can both locate the heartbeat and calculate the rate correctly. I smiled to myself, recalling my equine physical exam labs where I just pretended to avoid the scrutiny of an overbearing instructor.

Twenty minutes later, my ears were numb from the stethoscope earpieces, but Louie remained on his feet. All we could do was wait, and hope that Louie's spleen would politely move out of the way of his displaced colon.

Louie continued to look uncomfortable, pawing and the ground and hanging his head. Murmurs began among the techs, and Dr. I contacted the surgeon on call to let him know that there might be an abdomen to cut.

Luck was on Louie's side, however, and after around 45 minutes, the left abdomen ping was gone. In its place was a reassuring dull thud. Louie stopped pawing the shavings in his stall, picked his head up, and started engaging with his owners who were standing outside his stall. Ultrasound confirmed that the distended, gassy mass was no longer where it had been. Score one for medical colics. Dr. I called the surgeon back to put him off guard, and the techs breathed a sigh of relief.

Since Louie's colon could technically displace again, we needed to monitor him every few hours until the morning. We wouldn't feel really confident until we saw real, formed manure. I pulled the 4 AM shift. When my alarm went off, I heaved myself out of bed, reflecting on how much worse this would be either not in California, or not in June.

In Louie's stall, I found a different animal than the dumpy horse of that afternoon. He even looked bigger, holding his head up and greeting me at the stall door. Soon after I haltered him, it became clear that Louie was hungry, and he had just about had it with my not feeding him. As I listened to his heart, he pawed the ground in a way that was more threatening and less pathetic than his previous leg movements. As I performed the important auscultation of his GI quadrants, he raised each hind foot in warning, one for each side I ausculted. Although this was no way to treat a person at 4 AM, I was just glad that he showed no signs of pain. Best of all, by 7 AM he had passed two piles of manure, to hallelujahs that only veterinarians can hear.

Louie just got better from that point. By better, I mean pushier. In fact, Louie and I had several disagreements today, over whether I was allowed to examine him, who would exit the stall door first, how fast we were going at the hand walk, which direction we were going at the hand walk, and whether it was okay to drag me over to a patch of grass so he could stuff his face. I remembered a trick from my dog training days; whenever Louie started going faster than I wanted him to, I turned around and we went the other direction. It worked somewhat, but by the end of his brief walk-and graze, Louie and I were glaring at each other pretty hard.

What I got out of this experience, aside from confidence in taking heart rates, is reassurance that I like the pace of an urgent problem. This is not how I would have described myself previously, but I do. I like being able to see a problem and work out what is going wrong and what has to happen to make it right. Perhaps most obvious, I hate being bored, and an emergency is the opposite of a slow day at work. I learned that I like medicine, and that I have only just scratched it's surface. I also learned that I can often rely on my knowledge, even though it is only the knowledge of a first-year veterinary student. I identified the nephrosplenic entrapment immediately when it was described to me, and I heard that ping. This is a very small deal, but it is a very big reassurance that my work will have tangible returns.

Tomorrow Louie will return home, and I will not be sad when it is not my job to walk him and haul his nose out of the buckets of hay, potted plants, and grassy patches. He will be glad to return to his life jumping fences with his teenager and never again letting me touch his abdomen with that cold metal thing. Maybe we'll glare at each other a little bit as his trailer pulls away.

No comments:

Post a Comment