Drug Testing and Prepurchase Exams for Horses

A 10 year old, warm-blood mare presented to PHD veterinary services for a prepurchase exam. The standard exam, complete with limb flexion was performed and the mare was found to be completely sound and negative to limb flexion. The buyer requested baseline radiographs of both hocks and both front feet. In addition, it was strongly recommended that a drug screen of the mare's blood be performed for the detection of sedatives, anti-inflammatory medications and corticosteroids.
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Figure 1

Although the mare was sound and did not resent limb flexion, there was radiographic evidence of advanced osteoarthritis of the lower hock joints.  In Figures 1,2, and 4, the yellow arrows are pointing to radiographic changes consistent with arthritis along the front or dorsal aspect of the lower hock joints. There is new bone growth (osteophytes) and joint space narrowing. In addition, in Figure 3, the blue arrows are pointing to the area of sclerosis surrounding the lower hock joints which suggests chronicity of the arthritis and the apparent "fusion" of the distal hock joints. These radiographic changes are advanced and are surprising considering that the mare was sound for the prepurchase exam.

Figure 2

Figure 3

Even though the mare was sound, I did NOT pass this horse for sale and intended use based on radiographic findings and advised the buyer to at least wait for the drug screen results prior to making their decision!   The standard drug screen takes approximately 5-7 days for results to be reported. Interestingly, the mare's blood tested positive for high doses of an anti-inflammatory medication which likely explains why this horse was sound and negative to limb flexion even though she has advanced arthritis in the lower hock joints. This case represents yet another example of the importance of drug testing and base line radiographs for prepurchase exams!! Admittedly, it is a financial slippery slope once you begin the radiographic exam regarding how many areas to evaluate, however; areas of high probablity such as the hocks and front feet should always be considered!

Figure 4

Summer Sore Time is here!!

Although I have already written a blog concerning summer sores in horses (go to: http://michaelporterdvm.blogspot.com/2013/06/habronemiasis-summer-sore-in-horse.html) , the condition is a recurring one and it deserves another visit!! Below are several images from different horses that suffer from recurring habronemiasis or equine summer sores. The horse in Figure 1 suffers from recurring habronemiasis in all 4 limbs, whereas the horse in Figure 2 recently developed summer sores along his sheath!! These summers sores are medium in size and treatable with topical and systemic medication. However the horse in Figure 3 is suffering from a horrible summer sore of his lower limb that has not been treated but allowed to grow unabated and permanently disfigure the limb. It is frustrating to the horse owner that these lesions tend to return every year with the return of flies however if treated early and aggressively, management of this condition is quite do-able!!

Figure 1

Figure 2

For horses with recurring or first time habronemiasis, I recommend the following:

1: Systemic treatment with a dewormer containing Ivermectin. Treat twice, approximately 3-4 weeks appart.
2: Topical treatment with Dr. Porter's summer sore cream!!
3: If the summer sore is excessively large or in a location that is difficult to treat with topical medication, I recommend systemic therapy with corticosteroids. I prefer to medicate with a tapering dose of oral prednisolone over 30 days.

It is critical that the barn management incorporate a fly control program of their choosing. In addition, horses which suffer from recurring summer sores need to be treated the moment there is any redness or mild irritation present in the old summer sore sites!! If treated early, the lesion will typically respond favorably to topical medication without the need for systemic corticosteroids! 

Figure 3

Sarcoid Tumor in a Horse

A middle-aged gelding presented to PHD Veterinary services for the removal of a large tumor from the base of the right ear (Figures 1 and 2). Two years prior, a smaller tumor was surgically removed from the same ear. The histological report was consistent with a sarcoid tumor. At the time of the original surgery, several sarcoids were removed from different areas including the pectoral region and groin area. The recurring sarcoids were treated with intra-lesional chemotherapy, cryotherapy, topical medications and systemic herbal remedies. At presentation, a large, lobulated tumor was "hanging" from the base of the right ear. There was mild hemorrhage and evidence of moderate necrosis of the tumor. The gelding was resistant to manipulation of the tumor however gentle palpation of the ear noted that the tumor was NOT attached to the cartilage portion of the ear but only the skin and immediate subcutaneous tissues.

Figure 1

Figure 2

The gelding was rendered unconscious via injectable anesthetics and the tumor was removed through a large incision (Figure 3 and 4). Moderate hemorrhage was encountered confirming that the tumor was highly vascular. The incision was partially closed with sutures and the horse was recovered from anesthesia. Examination of the tumor after removal noted it consisted of 3 individual masses and weighed more than one pound (Figure 5).

Figure 3

Figure 4

Figure 5

This case represents an extreme example of recurrent sarcoids in a horse. Per the owner, the previous management of the sarcoids were initially effective however in time the tumors returned. The removal or de-bulking of the ear-based tumor will most likely not be sufficient in keeping the sarcoid tumor from removal. Aggressive therapy involving intra-lesional chemotherapy agents and cryotherapy will be employed to keep these tumors from continuing the develop!!

Figure 6

 Fast forward 6 weeks and the surgical wound is in the process of healing nicely (Figure 6), however there are several small sarcoids along the tip of the ear and also within the surgical site that are inflamed and beginning to grow. Follow-up treatment included the injection of cisplatin directly into the small sarcoids. Unlike the initial procedure which was done under anesthesia, the cisplatin injection was performed with sedation and a local "block" of the ear. Two weeks after the cisplatin injection, the small sarcoids along the tip of the ear are shrinking however the sarcoids within the surgical site remain inflamed  (Figure 7).

Figure 7

 Hence, the small sarcoids were treated with cryotherapy and the picture in Figure 8 was approximately 2 weeks post cryotherapy. The initial surgical site is a scar and all of the small sarcoids are regressing nicely. This horse will be monitored very carefully to make sure that any new sarcoid growth is treated aggressively!! This case represents an excellent example of the need for early, aggressive and multi-drug treatment of sarcoids in horses.

Figure 8

Atrial Fibrillation in a Horse

 An 18 year-old gelding presented for a pre-lease exam. The horse was sound and displayed no clinical abnormalities. However, when the heart was auscultated the heart rhythm was abnormal. Normally, a horse's heart sounds like two distinct sounds, otherwise known as the "lub-dub". These two sounds correspond to the opening and closing of specific heart valves during contraction and filling of the heart's chambers . There are actually 4 heart sounds but typically we only describe the "lub-dub". In a normal horse, the number of lub-dubs that are counted in a minutes range between 28-40 lub-dubs or beats per minute and they should be equally spaced in time. The electrocardiogram (EKG) in Figure 1 is that of a normal horse. The red arrows correspond to the contraction of the ventricles and the green arrows correspond to the contraction of the atrial. Normally, the atria contract first followed by the contraction of the ventricle. The blue arrow corresponds to the time between ventricle contractions which should equal the heart rate or number of lub-dubs auscultated in a period of time. Notice that the blue arrows are equal in length between heart beats AND that there is one green arrow for every red arrow!!

Figure 1

The lub-dubs for this particular horse were irregular and there was no predictability of their irregularity hence the heart rhythm was described as "irregularly, irregular". This type of heart arrhythmia is consistent with a condition known as atrial fibrillation. In Figures 2 and 3 notice that the blue arrows which correspond to the time between heart beats vary significantly. Equally important, there appears to be many more green arrows (Figure 3) than red arrows. This would suggest that the atria is contracting more often than the ventricles, hence the term atrial fibrillation!!

Figure 2

Figure 3

 Atrial fibrillation in horses is not uncommon and young horses with this condition are often asymptomatic. Thoroughbreds are diagnosed most often and when it is diagnosed in younger horses, the cause for the arrhythmia is often not determined. However, in older horses underlying heart disease is often associated with atrial fibrillation.  The most common clinical complaint would be exercise intolerance and decline in performance. In addition, an elevated resting heart rate may be indicative of early congestive heart failure as well as persistently distended jugular veins (Figure 4). Diagnosis of atrial fibrillation requires an EKG and a cardiac ultrasound is recommended to determine if there is underlying heart disease. Often a 24 hr halter monitor (Figure 5) may be used to better describe the horse's 24 hr cardiac cycle. There are several methods available to try and "convert" a horse with atrial fibrillation. However, it is important to first determine that cardiac disease nor electrolyte disturbances are the root of the problem. The methods include various medications and electrical cardi-conversion.  Prognosis for horses with atrial fibrillation depends on whether the horse has underlying cardiac disease. In the case of cardiac disease, the prognosis is poor; however, in young horses with idiopathic atrial fibrillation, the prognosis can be good for full return to work as a sport horse!! This case re-inforces the need for a solid physical exam on a regular basis to make sure this type of disease does not go undetected!!
  

Figure 4

 

Figure5

Superficial Flexor Tendonitis in a Horse

A middle-aged gelding presented to PHD veterinary services for tendonitis of the superficial flexor tendon (SDF). The tendonitis was a result of an tendon-sheath penetrating injury and was associated with a severe tendon sheath infection. The tendon sheath infection was treated aggressively and effectively by an equine surgeon. An ultrasound exam was performed along the plantar aspect of the hind fetlock and a large, core-like lesion was identified (Figure 1, black area within red circle). The lesion consisted of disrupted tendon fiber and edema. Several options were considered to help the "healing process" involving the SDF tendonitis. These included extra corporeal shock wave treatment, platelet rich plasma (PRP) injection, stem cell injection, and/or concentrated bone marrow injection. The decision was made to treat the lesion by injecting a mixture of concentrated bone marrow mixed with PRP product. The bone marrow was collected from the horse's sternum and concentrated on site (Figure2). In addtion, a blood sample was collected from the horse and PRP was harvested on site. The PRP was mixed with the concentrated bone marrow and then injected into the lesion via ultra-sound guided technique.

Figure 1

Figure 2

In addition to the PRP+bone marrow injection, the horse was fitted with a corrective shoe that provided significant heel extension (Figure 3 and 4). This type of shoe is also known as a "fish tail" show and will reduce the "load" across the fetlock joint by supporting the lower limb. Horses recovering from tendon sheath infections and SDF tendonitis tend to avoid fully loading the back of the foot which may result in lower limb contracture. The fish tail shoe allows the horse to fully load the foot in a more comfortable fashion. The horse was walked daily and otherwise kept in stall confinement. In addition, the leg was treated daily with cold compresses.

Figure 3

Figure 4

Approximately 30 days after the PRP+bone marrow injection, the horse's limb was re-ultrasounded. There has been significant "filling in" of the lesion (Figure 5). Although the area that was the lesion (red circle) remains identifiable, there has been a significant improvement in tendon fiber alignment and the edema (black) has nearly completely resolved! Although this represents a tremendous amount of improvement in just 30 days, there remains a significant period of rehabilitation before the ultimate out come of this case can be reported.  This case provides an example of a regenerative therapy that combines PRP and progenitor stem cells (bone marrow) for the treatment of tendonitis! The advantages of this approach versus stem cell treatment include reduced cost, on site harvesting and same-day treatment.

Figure 5

Ethmoid Hematoma versus Paranasal Sinus Cyst in a Horse

Two horses presented to PHD Veterinary services for the same complaint of "no air moving through one of the horse's nasal passages!" Both horses had a history of mild to moderate nasal discharge that had increased slowly over the past 6 months. On presentation, a simple evaluation of air passing through the nasal cavities revealed that there was NO air moving through the affected side on each horse however, endoscopic exam revealed a unique problem in each horse.

Figure 1

 In Figure 1, a smooth, white soft tissue mass was identified within 2 inches of the opening of the nasal cavity. This soft tissue mass was completely obstructing the nasal passage. In addition, when the scope was passed through the unaffected side, the soft tissue mass was noted to be extending into the naso-pharynx suggesting that the soft tissue mass extended through out the entire nasal passage (Figure 2). In Figure 2, the white wall of tissue noted along the right side of the image is the soft tissue mass as it extends into the naso-pharynx.The soft tissue mass is most likely consistent with a paranasal sinus cyst however surgical removal will be required to confirm the diagnosis. These types of cysts develop in young horses and grow slowly over months and years until a clinical problem develops. Surgical removal provides complete resolution of these types of cysts!!

Figure 2

Figure 3

In the second horse, a large golden-colored soft tissue mass was identified in the region of the nasal passage closest to the naso-pharynx. There was more discharge associated with this soft tissue mass and small areas of hemorrhage were noted. The soft tissue mass was completely obstructing the nasal passage and was originating from the ethmoid turbinate region which most likely classified it as a ethmoid hematoma!! These types of tumors typically present with a complaint of a unilateral bloody nasal discharge for months before they completely obstruct the nasal passage. However, they can be fast growing tumors and require an aggressive approach to eradicate. Treatment may involve either surgical removal or repeated injections of formalin. It has been my experience, having injected several horses for YEARS, that the tumors tend to return with this approach! Hence, I recommend surgical removal when first diagnosed, especially if the tumor is invading the sinus cavity or the naso-pharynx.

IIeal Hypertrophy in a Horse

A 10 year old Paso fino mare presented for recurrent colic for several months duration. The mare had a long history of being a "hard keeper" but in the past 3-4 months had begun to colic after each feeding. The mare was fed a diet of senior feed plus free-choice coastal bermuda grass hay. The mare was referred to PHD Veterinary services for a gastroscopy (stomach scope). The mare presented with a body condition score of 3 out of 9. The client reported that the mare had a good appetite yet shortly after eating, the mare would develop signs consistent with abdominal discomfort! The gastroscopy was normal therefore we opted to ultrasound the mare's abdomen.  In Figure 1 there is a cross-sectional image of a loop of intestine (black circle) that is grossly abnormal. The lumen (center) is completely filled in with soft tissue(grey area). The filled in center in Figure 1 corresponds to thickening of the small intestine which likely results in delayed passage of ingesta. Interestingly, there was only 1 very distinct area of the small intestine that scanned abnormally thick. However, there were several loops of small intestine that were dilated and had diminished peristalsis (Large black circles in Figure 2).

Figure 1

Figure 2

The ultrasound findings were consistent with a focal area of thickened small intestine and a large area of dilated small intestine. The dilated small intestine were likely "up stream" from the thickened small intestine and were as a result of partial obstruction of the thickened small intestine. Based on these findings, the mare was referred for abdominal exploratory surgery. During the abdominal exploration, a very thick region of the small intestine was identified. This region corresponded to the ileum which is the very final section of the small intestine. Approximately 12 inches of ileum were grossly thickened resulting in minimal lumen formation for passage of ingesta (Figure 3). Normally, the ileum is a wide-open tube as depicted in Figure 4!! Unfortunately, due to the severity of the condition, poor prognosis, and financial limitations, the mare was euthanized on the surgical table. Ileal hypertrophy has been reported in horses consuming coastal bermuda grass hay and it is theorized that some horses develop an "allergic" response to coastal hay resulting inflammation of the ileum and ultimately gross thickening. More commonly, colic symptoms associated with coastal hay is due to poor quality hay rather than ileal hypertrophy. However, any horse with chronic colic symptoms that is consuming coastal bermuda grass hay should be evaluated for this condition. 

Figure3

Figure4

Thin Soles in a Horse!!

The radiographs below in Figures 1-3 belong to a middle-aged QH gelding that presented for severe lameness. The gelding was recently trimmed by the farrier and had a history of mild to moderate foot pain.
On presentation, the gelding was very sore when asked to walk on a firm surface and was not willing to walk in a tight circle! There were NO pounding digital pulses however firm pressure, via my finger tips, over the sole region resulted in a strong pain reaction by the gelding. Radiographs were taken and severely thin soles were diagnosed in both front feet (Figure 1 and 2). The actual thickness of the sole was difficult to measure due to the thinness but was approximated at 2-3mm (Figure 3). Less than 5mm of thickness essentially corresponds to 1 swipe with the hoof knife!!

Figure 1

Figure 2

Figure 3

In Figure 4, there is a radiograph of a normal horse's foot. The sole depth at the toe region is approximately 15-20mm. In my experience, when the sole thickness is less than 10mm, there is increased likelihood of foot pain from concussion with the ground. Thin soled horses are at high risk for sole bruising and sub-solar abscess development. Unfortunately, some horses are "naturally" thin soled due to poor genetics and MUST be managed with shoes. The corrective shoeing is simple and may include a rim pad, leather pad , or soft pour-in pad. I strongly recommend radiographic evaluation PRIOR to any foot trimming to determine the sole thickness of horses that have a history of chronic foot pain!

Figure 4

Equine Hock Arthritis

Figure 1

The radiograph above (Figure 1) is of a horse's hock or tarsus. This view is also known as the "Lateral" view or side view. The equine hock joint is made up of 4 individual joints which are labelled above. The bottom two joints are also known as the distal hock joints and include the distal inter-tarsal joint (DIT) and the tarsal metatarsal joint (TMT). When "injecting" hocks, these are the most common joints treated and are often referred to as the "upper and lower hock joints". Degenerative joint disease (DJD) or osteo-arthritis is most common in the distal hock joints and  often results in poor performance plus/minus lameness. Bog spavin is the term that refers to increased joint fluid within the tibiotarsal joint. This is the "high motion" joint of the hock and is NOT commonly injected with "hock injections". However if increased fluid is noted, a radiographic exam is definitely indicated prior to instituting a treatment plan. Generally speaking, arthritis of the distal hock joints is more acceptable and can be managed with intra-articular therapies. However, arthritis of the tibiotarsal joint and/or the proximal inter-tarsal joint is more concerning and is reason for concern when predicting future performance.

Figure 2

In Figure 2 and 3, there are radiographic changes that indicate osteo-arthritis of the tarsal metatarsal joint space. These changes were noted during a prepurchase exam of a 5 year old horse. The horse was sound during the exam and did NOT respond to hock/stifle flexion. The million dollar question is what to recommend to the buyer based on these findings. In my clinical experience, most horses with these changes will eventually need intervention via intra-articular cortisone injections. I believe that horses with these changes are MORE likely to need hock injections than those with "normal" radiographs. However, these findings are not necessarily a negative prognostic indicator with regards to the horse's future performance. 

With management, i.e, hock injections, these horses can compete at the highest level and succeed!  As such, these findings do NOT constitute a FAILING grade during the prepurchase exam however the buyer needs to be prepared for the strong likelihood of routine "maintenance". This can easily result in hundreds to thousands of dollars per year that should be considered into the price of the horse. 

Figure 3

High Ring Bone!!

The radiographic image below is of the right hind pastern of a 4 year old mare that presented for a prepurchase exam. The mare had only been under saddle for 6 months. During the active exam, the mare cross-cantered when lunged to the left. In addition, the pastern area was "thicker" when compared to the opposite hind limb and the mare was moderately positive to flexion of the limb in question. Due to the suspicion of a significant problem, the right hind pastern was radiographed. The yellow arrows highlight new bone growth along the edges of the pastern joint. The bone growth or osteophytes are large and proliferative. These findings are indicative of advanced osteo-arthritis of the pastern joint otherwise known as "high ring bone". 

Figure 1

In Figure 2, the same osteophytes are noted as the course around the front of the pastern joint. The yellow arrows point to the osteophytes or irregular "white" structures along the edge of the pastern joint. 

Figure 2

Figure 3 and 4 are radiographs of a normal pastern joint. There are no osteophytes noted along the margins of the pastern joint. Notice in Figure 4 the smooth, curved border of the normal pastern joint. Interestingly, the pastern imaged in Figures 3 and 4 was radiographed because it palpated "thicker" than the opposite limb. Fortunately, there was no evidence of pastern arthritis. 

Figure 3

Figure 4

 In Figure 5 there is significant new bone growth or osteophyte development along the margins of the coffin joint. This is known as "low ring bone". Generally speaking, "high" or "low" ring bone is a significant finding during a prepurchase exam. Low ring bone is more common in draft breed horses. In addition, varying degrees of coffin joint arthritis, in active sport horses, is more common than pastern arthritis.

Figure 5

 High ring bone or pastern arthritis should be a concerning finding in any horse that is expected to carry a rider. Medical management of pastern osteoarthritis is limited to intra-articular treatment with cortisone or regenerative therapies. Unfortunately, the degeneration of the joint progresses rapidly and commonly results in chronic lameness. Surgical management involves fusion of the joint either with hardware or chemicals.

Kissing Spines!

The radiographs below are of the dorsal spinous processes of  the vertebral bodies in the top-line of a horse. Essentially, these bones are directly below the saddle and directly below the rider's center of gravity. As such, they represent some of the most stressed areas during riding under saddle. The first two radiographs are of the same horse and the yellow circles correspond to where the spinous processes are in contact with the each other. This is also know as "Kissing spines". This horse presented for a chronic history of a tender back and unwillingness to move forward at the trot and/or canter. The 3rd radiograph is that of a normal horse. There is significant space between the spinous processes. These spinous processes are slightly cranial to the ones depicted in the previous 2 radiographs.  Unfortunately, the diagnosis of kissing spines is not favorable for the horse to have a performance career without chronic back pain. There are therapies aimed at reducing the pain and muscle spasm associated with this condition which include; saddle fitting, shockwave therapy, mesotherapy, acupuncture, chiropractic adjustment, deep message, and cortisone injections. I strongly recommend having radiographs taken of any horse with a chronic history of back pain to determine if this might be the cause!! 

Mesotherapy 

These small bumps were caused by micro-injections of medication just under the skin, or also known as Mesotherapy. This treatment has been used effectively for over 30 years in humans and horses. The primary objective of this treatment in horses is to block or break the pain cycle associated with chronic back pain. 

Technically, mesotherapy treatment stimulates the mesoderm or middle layer of skin by stimulating the giant fibers present within this layer of skin. Commonly, a combination of lidocain and dexamethasone is injected via multiple extra small needles (30g). These micro-injections result in stimulation of the giant nerve fibers located within this layer of skin that also communicate with major nerve tracts within the spinal chord. These nerve fibers INHIBIT the conduction of pain signals to the brain.

Typically, one or two mesotherapy treatments are applied to a horse's back and often are combined with shockwave treatments. Mesotherapy is used primarly as an aid to alleviate back pain followed by treatment of the primary cause of the back pain/spasm. This typically involves a source of lameness in either the forelimbs or hindlimbs. In addition, osteo-arthritis of the thoraco-lumbar spine and "kissing spines" are causes of chronic back pain. 

The response to mesotherapy is usually within 2-3 days and may last for 3-4 months.