Link: In thinking about the future of veterinary medicine…

The Dog Zombie just published a post describing their feelings as they finish Vet School. It’s a profound and inspiring essay, and I encourage everyone in my position, anxiously awaiting if you’ll get to attend school this year, to give it a read. I personally hope DZ will be hiring when I graduate, or even giving the commencement when I walk.

The post is titled “Navel Gazing with a Dog Zombie”

Ovariohysterectomy versus ovariectomy, is removal of the uterus necessary?

Ah, United States’ medicine vs. European medicine, the war rages on. The battleground I’ll discuss today: elective sterilization of the female reproductive tract.

Image from Penn State Virtual Cat Dissection

This discussion came up in JAVMA recently, and I felt it warranted a look from a future vet. Granted I don’t have all the information and education here, but given that I’ve only ever seen ovariohysterectomy performed in practice, I’m interested in why we actually choose to remove the uterus as well.

Much of the article discusses the benefits gained from the simplicity of the ovariectomy procedure. With the potential to use laproscopic techniques, smaller incisions, and less manhandling of the abdominal cavity, post surgical pain and complications can be markedly reduced in both cat and dog patients. More specifically, better exposure of the ovarian pedicle due to the incision location allows for complete excision of the ovary, suggesting that the surgeon will be less likely to leave any remaining endocrine tissue.

Outside of the surgery itself, the authors discussed the often cited benefits of spaying companion animals, and how the two techniques alter the statistics. Unfortunately, there were little to no studies directly examining the incidence of these benefits when comparing groups with or without a uterus, and some of the numbers they did find were inconclusive or conflicting. I found it interesting to see some of the actual odds concerning the prevented conditions we advertize when discussing spays, the most common being mammary and uterine tumors.

The potential for mammary tumors seems to be the most significant of the spay benefits. Their overall incidence is 3.4%, with 41-53% being malignant (DeTora, 2011). If spayed before first estrus, that risk drops to 0.5%, which is huge! Almost all of the benefits from spaying come from the removal of sex hormone cycling, which seems to be largely necessary for many of these tumors to form (not surprising, as I had previously discussed how estrogen appears to have an immune boosting effect, which would promote chronic inflammation that we know to be an important risk factor for many cancers). The authors point out that as hormone cycling is prevented solely by removal of the ovaries, that all of the future medical benefits of sterilization are gained without removal of the uterus.

The only medical benefit correlated with sterilization that is obviously tied to removal of the uterus seems to be uterine neoplasia.  However, most uterine tumors are benign, with only 0.003% being malignant as well as easily treated with hysterectomy (DeTora, 2011). The authors also found no case of uterine neoplasia ever reported in a dog that had had its ovaries removed before 2 years of age, making this benefit of ovariohysterectomy moot.

While I do think that the authors wrote this commentary with an obvious preference for ovariectomy, the assumptions they made seem rational; and even though there wasn’t enough data to declare one technique superior to the other, I agree with the conclusion that the United States’ preference for ovariohysterectomy cannot be supported by the currently available evidence. However, there is no obvious disadvantage to the procedure, and whichever technique that specific surgeon is most proficient with will probably be the best choice in any situation.

 

ResearchBlogging.orgDeTora M, & McCarthy RJ (2011). Ovariohysterectomy versus ovariectomy for elective sterilization of female dogs and cats: is removal of the uterus necessary? Journal of the American Veterinary Medical Association, 239 (11), 1409-12 PMID: 22087712

Newsworthy: Veterinarians Find Infections Faster by Monitoring Nt-pCNP

"Stinger", a dog with sepsis from a bite wound. Image from Valley Center Veterinary Clinic, Valley Center, CA.

N-terminal portion of pro C-type natriuretic peptide. Try to say that one three times fast. ScienceDaily has a cool article detailing a couple new studies showing that this peptide (Nt-pCNP) could be a solid indicator of sepsis as opposed to a generalized inflammatory response. It could potentially be added to current serum chemistry analysis, or packaged as an ELISA snap for quick, in-house diagnostics for pertinent cases.

Overuse of antibiotics has been a long term problem that is being well addressed in human medicine, however they are used much more broadly and liberally in animals due to their non-prescription access (especially in large animal work), and their use as a diagnostic tool for patients who can’t speak and often can’t afford thorough diagnostics. A veterinarian who’s client is unwilling to pay for a culture will often send broad spectrum antibiotics home anyway as a less expensive option in the hopes that they will take care of the problem.

I was unable to find a chemistry profile of Nt-pCNP, but the journal article itself talks a bit about C-type natriuretic peptide. CNP is produced by vascular endothelial cells and immune system macrophages. It “inhibits microbial growth and modifies pathogenicity of microorganisms” (DeClue, 2011). The problem with looking for just CNP as an indicator of sepsis is that it has a very short half life, and tends to degrade even faster in removed serum. Therefore, the researchers decided to use Nt-pCNP as their target molecule.  Nt-pCNP is created in a 1:1 ratio with CNP as a byproduct, and is much more durable and long-lived in both the bloodstream and collected serum.

The results of the study support the hypothesis  that CNP is a good indicator of sepsis, however like anything else, it’s not ideal. CNP was shown to be a poor indicator of sepsis when the infection was peritoneal. This includes gastrointestinal perforations or other possible infections found within the peritoneum (the authors mention that using peritoneal fluid as opposed to serum from a distal point may yield better sensitivity). Taking these false negatives into account, the test had a 65.5% sensitivity, for all other origins of sepsis in the study, sensitivity was 92%. Unfortunately, there appears to be a large potential for ambiguous negatives when peritoneal infection is suspected, but it’s always important to remember to educate clients that medicine is rarely black and white. It’s nice that House is able to identify exactly what’s wrong with each of his patients every week, but most of the time, we’re just going to give them supportive care based on the most likely result. Some of the limitations of the study that the authors mentioned were the small sample size and uncontrolled natures of the ailments that may have influenced the blood chemistry (samples taken from bacterial vs. viral infections, condition as of admission, underlying secondary infection or ailment, etc.).

In the case of this test and many other lab tests, positives are very definitive and help us out, while negatives are ambiguous. This is true whether it’s a heartworm test, fine needle aspirate, fecal flotation, radiology, or any number of other diagnostic tests. Every one is a tool, and hopefully looking at Nt-pCNP levels will give us another way to confirm sepsis while our cultures are growing at the lab, or perhaps offering another faster or less expensive option that the situation necessitates.
This post was chosen as an Editor's Selection for ResearchBlogging.org
DeClue AE, Osterbur K, Bigio A, & Sharp CR (2011). Evaluation of serum NT-pCNP as a diagnostic and prognostic biomarker for sepsis in dogs. Journal of veterinary internal medicine / American College of Veterinary Internal Medicine, 25 (3), 453-9 PMID: 21457321

Article review: Effects of early pregnancy diagnosis by palpation per rectum on pregnancy loss in dairy cattle

Image from UPenn

Just a short one here today. Not too much interesting going on in a study that supports the null, but the methods are great.
This study looked at the affect that one or two rectal palpations to determine pregnancy had on embryo viability. I can see why there would be a question, it seems like a highly invasive procedure when you’re shoulder deep in cow rectum and feeling for an amnion several layers of membranes away. But we tend to anthropomorphize, and many dairy cattle require minimal restraint for the procedure. Nonetheless, it does seem likely that there could be a negative effect on the embryo, especially when rupturing or crushing the amnion via rectal palpation has been a historical method of terminating an unwanted pregnancy in cows (before we started using PGF2α) (Romano, 2011).
The study did a great job of identifying factors that have created conflicting results in the past. Whether that was sampling bias, uncontrolled treatments (multiple people and techniques for palpation), or a lack of a true control. They took the time to show how each one of those shortcomings was corrected in this study, and I think they did a great job designing the experiment.
In the end it was surprising to see that there was no difference between the cows subjected to rectal palpation once or twice compared to the control. I didn’t expect to see a significant difference, but potentially a small one. The authors did warn that because this experiment was so controlled, the results may not be similar to every situation. Inexperienced personnel or different techniques could change the pregnancy rates in practice (the study employed a single veterinarian with >25 years experience). One difference they took time to note was the much lower pregnancy rate in dairy cows as opposed to primiparous heifers. The exact etiology of this is unknown, but is commonly found in dairy. The authors mention it as it played a role in their analysis of the two farms involved (other factors affecting rates between the farms were geographic area, rate of twinning, and breed of cattle).

Not especially exciting, but it’s always great seeing researchers identify a conflicted area and tackle it with strict methods/controls and a large sample size.

ResearchBlogging.orgRomano JE, Thompson JA, Kraemer DC, Westhusin ME, Tomaszweski MA, & Forrest DW (2011). Effects of early pregnancy diagnosis by palpation per rectum on pregnancy loss in dairy cattle. Journal of the American Veterinary Medical Association, 239 (5), 668-73 PMID: 21879969

Article Review: Epidemiology of Surgical Castration in the United States

I recently had a professor tell me that if I didn’t let them know if I made it into vet school, they would forever curse me with fat, in heat, Labrador spays for the rest of my career. I can think of few fates worse for a future veterinarian (though I did mention that the owners also had to have  no way to pay, and will forget to mention this until after the procedure). Today’s article is really cool and discusses the prevalence of ovariohysterectomy and orchiectomy (spaying and neutering, fixing, castration, gonad removal,de-nutting, whatever you prefer to call it) in the USA. It breaks the percentages down into region, animal species, animal breed, animal age, and enrollment in wellness plan from Banfield (animal health insurance).

Banfield Pet Hospital is an amazing organization for animal research because all of their records are computerized and kept in a central database (I should mention that the man who made Banfield what it is today is an OSU alum, go beavs). Because of this treasure trove of data, this study was able to get a sample size of over 300,000 cats and over one million dogs. While this represents less than 1% of the US pet population, its still a valuable amount of data, and we can reasonably assume that Banfield has a decent representation of the rest of the pet population that regularly visits private clinics. The article mentions that one of the only large differences is the mean age at clinics (Banfield’s is slightly lower). The numbers found in this study also line up well with previous examinations using distributed surveys to collect data.

I’m very proud to say that the Northwest region (making up Washington, Oregon, Idaho, and Montana) has the highest percentage of castrated cats and dogs compared to any other region (tied with the North Central region for percentage of dogs) according to the study. The region with the lowest percentage was the Southeast region (making up Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, and Tennessee). That’s an area of the country I haven’t ever visited, so I can’t comment on cultural factors that may influence the decision to castrate pets, but clearly more outreach could be focused on that area.

The breed distribution is interesting, but doesn’t offer too much information for most breeds. In my own head I see the Labs’ and Retrievers’ high numbers understandable, as you can in some ways consider them “white-collar” or suburban dogs. This would be associated with a higher income and thus one less roadblock to castration. Pit Bulls can maybe be considered a “blue-collar” dog, but that can’t be the only reason their numbers are so low. I’m actually at a loss as to why the castration rate of Pit Bulls is so much drastically lower than all the others. It’s an obvious outlier. I myself love Pits and believe that in the right hands they make great dogs. But considering their stigma, low rate of adoption (and consequently high euthanasia rate), insurance liability, and higher risk, I do believe we should make castrating Pits a priority. I’ll definitely be looking for more literature that attempts to explain the demographics and other factors that create this problem. The second lowest group, Chihuahuas, is also interesting. Again, I’m not sure why the numbers for this breed are so low, but one factor may be that many Chihuahua’s are kept as indoor-only dogs, and that may reduce the motivation to perform the procedure, as the largest benefit is wasted on them (as seen by those owners).

I’m not surprised to see that mixed animals were more likely to be castrated, and I really have no problem with that. There aren’t too many unwanted animals that come from intentional breeding, and purebred animals generally don’t have trouble finding homes (pending behavioral issues). Responsible breeding doesn’t contribute to the pet overpopulation problem significantly, and leaving that option open to purebred owners is acceptable. With cats on the other hand, I’m happy to see the extremely high rate of castration. Cats are allowed to roam unsupervised much more than dogs, and we have enough trouble controlling the feral population without accidental pregnancies also occurring in animals that could have been easily castrated.

One rather frightening statistic was the percentage of dogs and cats from shelters that do not return for castration. This concerns me as in many cases the cost is free or subsidized to less than $50. In a private clinic you can pay upwards of $200, but this seems to be little incentive as 40-60% of animals are returned for the procedure when it is already paid for. To me, this is indicative that some of those owners will provide a low level of veterinary care for the lifetime of that animal, when they already haven’t taken advantage of a free procedure. This is pure conjecture however, and there could be a host of reasons that owners do not return. However, because the rate is so low, I would bet that there is some significant factor that is relatively consistent among owners who adopt from shelters, whether that be income (shelter’s are a very inexpensive option to get a purebred-looking dog) or attitude.

All in all, a good look at where castration is common, and where education and improvement needs to be made.  I do think that many PSA’s, advertizements, and advocacy campaigns are too often directed at groups that are already in agreement. Even looking the statistics from a PSA I made back in high school show that the primary people concerned with animal welfare are women over 35, and it’s clear that similar announcements are marketed at that group. New campaigns should focus on a new approach to educate people why castration is important, and maybe spend less time showing us pictures of sad puppies. Tell me why I personally should do it, because until it’s too late to change anything, there’s no reason I should think I’m part of the problem.

ResearchBlogging.orgTrevejo R, Yang M, & Lund EM (2011). Epidemiology of surgical castration of dogs and cats in the United States. Journal of the American Veterinary Medical Association, 238 (7), 898-904 PMID: 21453178

Article Review: Ocular lesions associated with systemic hypertension in dogs: 65 cases (2005–2007)

The first of a bunch of articles I recently picked out of JAVMA was interesting because while I never got any readings without some form of anesthesia, I imagine that hypertension was extremely common in many of the dogs I saw at Lapaw Animal Hospital. Whether it’s a result of obesity, illness, or hospital stress, systemic hypertension is usually an indicator of some other problem, and therefore important in the analysis of the patient.

Image from Conrad Weiser Animal Hospital

The article is a bit confusing, because it goes into great detail the different potential causes of both hypertension and ocular lesions, and the significance of the data based on which was diagnosed first with each case. I began to lose track when on one hand they would mention that the data may be too biased to determine a cause and effect relationship between the two symptoms due to a preexisting condition, but then also said that those preexisting conditions had such a relationship.  It does seem clear that ocular lesions are promoted by the presence of hypertension in both dogs and cats, while the disagreements in the literature are mainly in how much one is indicative of the other. The relationship of hypertension correlating with ocular lesions in cats has varied from 50-100%, which tallied with the frequency of 62% in this case review. While these frequencies don’t prove any sort of direct relationship, they do support the evidence we do have that hypertension can lead to ocular lesions, and that if one is discovered in a patient, it’s worth looking for the other.

This is the first case study I’ve looked at in detail, and I’ll certainly be reading more as I move into veterinary medicine. It was really interesting to me how they selected cases, and how thoroughly they reviewed the significance of possible bias in each case. I absolutely understand why it’s so important, and the way each patient is presented changes how each symptom is portrayed in relation to the others, which makes the range of values for this specific correlation so understandable. Owners are much more likely to bring their dog into the clinic when seeing a clouded or irritated eye

Image from Bass Lake Pet Hospital

than hypertension would be found during a routine exam. Then you have to examine old clinic notes to see if other conditions led to either event, or to see if the veterinarian made the assumption that they were related, and though the situation was resolved, no lab work supports their theory. Some of the limitations  mentioned in the study were the fact that they lad a low sample of normotensive dogs with ocular lesions, and that diagnosis of hypertension is difficult due to situational stress interpretation in the face of blood pressure values and varied measurements within the “grey area” of test results. They also did significant analysis within the cases that took into account patients that were taking anti-hypertensive drugs for other conditions, but mention that those patients might have skewed the data, because there is no way to ensure that there was owner compliance in administration.

An interesting note is that all 5 dogs in the study that were currently taking Phenylpropanolamine either acutely or chronically were all hypertensive, supporting anecdotal evidence that it can promote hypertension. This makes sense to me, as PPA is controlled due to its potential use in creating amphetamine, and its inclusion in many prescription stimulants (Adderall, etc.).

All in all, a good article, and a good look at the relationship between ocular findings and hypertension. Though a large part of me does feel for those research assistants at the University of Wisconsin School of Veterinary Medicine who combed through thousands of patient files to find these 65 cases.

ResearchBlogging.orgLeblanc NL, Stepien RL, & Bentley E (2011). Ocular lesions associated with systemic hypertension in dogs: 65 cases (2005-2007). Journal of the American Veterinary Medical Association, 238 (7), 915-21 PMID: 21453181

Article Review: Effects of intravenous administration of Lactated Ringer’s solution on hematologic, serum biochemical, rheological, hemodynamic, and renal measurements in healthy isoflurane-anesthetized dogs

Well, it’s about time I mentioned an article I didn’t particularly enjoy on here. It’s not like I think it’s a waste of paper, it’s an important topic, but it does nothing creative and does little to contribute to the understanding of the subject. The article looks at the effects of different rates of Lactated Ringers Solution administered while under isoflurane anesthesia. It uses healthy animals, discusses well documented effects in humans, and just reinforces common practice.

Lactated Ringers is the most frequently prescribed fluid for maintenance of homeostasis in surgery and pretty much any other health stress event. I know when any patient wasn’t feeling well from any situation at my clinic, we always administered LRS either through a catheter or subcutaneously for outpatients, the dosage based on weight and severity of condition. We know how to use it, and it’s gotten a proven history of effectiveness in both humans and animals. The article justifies itself by saying that fluid therapy in dogs is largely based on human evidence, and that the formulas we use to determine rates have not been thoroughly investigated. Yet throughout the article they repeatedly compare their results to similar studies, and make no conclusions that aren’t already accepted in human and animal medicine. Additionally, the gaps in the literature they identify can’t even be answered using the methods and results of this study, so you can’t use them to justify its existence.

So the big conclusions they determined were that providing LRS increased plasma volume and cardiac output, didn’t increase urine production, and appears to leave the blood volume and remain in extracellular space. These are important points, but they were accepted unanimously without the presence of this study. Further, if their goal was to confirm these assumptions, their results are pretty much irrelevant with a sample size of only 8 animals, all in perfect health, similar size (26-41 lbs isn’t a lot of variance in the world of dogs), and undergoing no medical stress other than common anesthesia and mechanical ventilation.

My impression after finishing the paper was that the people at QTest labs (associated with Ohio State University College of Veterinary Medicine) needed a study to do, needed to get a grant proposal ready, and did enough research on the subject to sell this trial. It’s well written and the authors do a great job of placing their results in context of the literature, mostly because it all agrees. But it can’t hide the fact that it does nothing revolutionary other than providing history on the subject, and giving an excellent account of the methods used in the study. With such great, specific, and controlled procedures, this facility could be solidifying other theories that have conflicting data, if they’d use a sample size large enough.  I’m sure that they don’t always do milk run trials such as this one, and I look forward to seeing their name again in future articles.

ResearchBlogging.orgWilliam W. Muir III, Anusak Kijtawornrat, Yukie Ueyama, Steven V. Radecki, & Robert L. Hamlin (2011). Effects of intravenous administration of lactated Ringer’s solution on hematologic, serum biochemical, rheological, hemodynamic, and renal measurements in healthy isoflurane-anesthetized dogs JAVMA, 239 (5), 630-637

Newsworthy: “White Coat Effect” and Dog Appeasing Pheromone

It’s tough being a big guy in veterinary medicine. I’m not sure why so many dogs don’t like guys, but its going to be a big hurdle for me as my work continues with both small and large animals. Just today I met someone’s dachshund who did nothing but chase my ankles barking, growling, and snapping his teeth. Any attention or efforts to be friendly only seemed to increase his wrath, and ignoring him completely just encouraged him to be more brave (and not in an investigative way, more of a tactical strike way). Most dogs who dislike men aren’t so overtly aggressive, and just feel uneasy or fearful. One of the ways we try to make these dogs more at ease, in many situations, is to use Dog Appeasing Pheromone. I’ve often suggested that I wear a DAP collar myself so that I can exude a calming presence and change my smell profile, because once they see me and decide to become anxious, DAP won’t do much good.

I was thinking about methods for calming animals after reading this article about the “White Coat Effect” in greyhounds. Just like in humans, greyhounds and other dogs get anxiety and higher blood pressure in response to the stimulus of the veterinary clinic and veterinarians. Anything from the smell of latex, seeing white coats and scrubs, or a combination of several factors could be the stimulus. Not every dog reacts this way, but I imagine most do to varying degrees. Whenever we get a high strung dog, we would spray the counter or a towel with DAP, and hope it helps. One of our veterinarians swears by it for her own dogs (border collies mostly), and I think that it makes a difference.

There are a couple studies that support the use of DAP in creating a calmer environment in different situations, and really, anything helps. For my part, I just try to do the obvious things to make myself less scary: look smaller, don’t face the animal, slow movements, soft voice etc.. My newest thing has been observational learning, so for example, if I can talk to the owner or interact with their other, less fearful animal, before even approaching the nervous dog/cat, I’m hoping that they may not generalize me as just another man.

All I can really hope for is that if I work long term in a clinic someday, I can build a relationship with both the clients and their animals. It may be that there will just be some patients that will be better served by seeing a female veterinarian, and that’s okay, not everyone can be a perfect fit. Hopefully though, working with larger animals will be a better fit for me as a veterinarian, and I’ve got a few more years to decide on my approach to alleviate the fear associated with my white coat.

Article Review: Leptospira and Leptospirosis

In my latest ScienceDirect purge, I came across this article covering Leptospirosis. I had no idea it would be such a dense read, figuring it would be a simple review of the disease with emphasis on new discoveries. I ended up using a lot of immunology references and Google searches. This article isn’t just an entry from the Merck manual.

The article does a very good job of covering Lepto microbiology, but I was especially impressed with the point they made to identify everything we don’t know. Indeed that was the emphasis of the article, that lepto contains so many pathways unique to it as a bacterium that we don’t know nearly as much about it as we do something like E. Coli. Additionally, Lepto is extremely hard to culture, as you end up with non-virulent colonies. They identify and isolate the virulent daughters by inoculating lab animals.

You might assume that immunity to Lepto is a simple thing, given how prevalent Lepto vaccination is due to the zoonotic risk. However the article makes the point multiple times that immunity to one Lepto serovar does not grant immunity to others, though occasionally it can help grant passive immunity or resistance across different species. While the exchange of genetic material between parent and daughter lepto colonies is not well understood, it appears to be slow mutating, which is interesting given how unique the antigens between serovars seem to be.

There’s a lot of complicated immunology discussed in the article that I don’t feel qualified to comment on, but it’s very interesting, and I recommend glancing through. The more microbiology I learn the more I understand that 99% of the workings of the cell happen on membranes (a statement that probably produces a loud “duh” from any student, biologist, or doctor). For a more clinical discussion of Lepto, a simpler reference like Merck or Blackwells will help, as well as several peer-reviewed sources that the article itself recommends for information on clinical presentations.

Adler, B., & de la Peña Moctezuma, A. (2010). Leptospira and leptospirosis Veterinary Microbiology, 140 (3-4), 287-296 DOI: 10.1016/j.vetmic.2009.03.012