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Friday, May 31, 2013

Distal Check Ligament Injury in a Horse

A 14 year-old, warm-blood mare presented for a sudden swelling along the upper region (2 inches below the carpus on the back of the leg) of the flexor tendons in the left forelimb. The mare was mildly to moderately positive to palpation of the swelling yet no obvious lameness was observed when trotted in hand. Careful palpation of the area isolated the swelling to the distal check ligament/deep digital flexor tendon area of the proximal metacarpus. Approximately 2-3 inches below the knee/carpus of a horse, 4 soft tissue structures can be identified on ultrasound exam (Figure 1). The ligaments and tendons are typically assessed in a cross-sectional plane (Figure 1-3) and in a longitudinal plane (Figure 4). The most superficial is the superficial digital flexor tendon (SDF), followed by the deep digital flexor tendon (DDF), followed by the distal check ligament, and finally the deepest soft tissue structure which is the proximal suspensory ligament. The first two structures (DDF and SDF) are tendons and should appear identical with regards to brightness (echogenicity) on ultrasound. The deep structures (check ligament and suspensory) are ligaments and tend to be brighter on ultrasound exam when compared to the tendons. The overall echogenicity should be the same or homogeneous throughout the body of the tendons and ligaments.

Figure 1
In Figure 2, a clear, black lesion is identified along the outside/lateral aspect of the distal check ligament. The entire image appears slightly side-ways or oblique in order to optimize visualization of the ligament injury (Red circle in Figure 3). The "black hole" or core lesion corresponds to an area of ligament fiber disruption, edema, and possible blood accumulation.

Figure 2
Figure 3

In Figure 4, the same area is examined in a longitudinal plane to assess the extent of the fiber disruption. The area of disrupted ligament appears to include nearly the entire length of the distal check ligament. Although there is significant edema and contrast between the check ligament and the surrounding structures, the ligament appears to be intact. On a scale of mild, moderate, and severe, I would grade this as moderate with regards to degree of injury to the distal check ligament.

Figure 4
The image in Figure 5 is a simultaneous cross sectional and longitudinal image of the injured ligament.  Of all the soft tissue structures to injure in this region of the horse's limb, the distal check ligament is the least important with regards to long term prognosis and return to work. In my experience, many horses with this injury demonstrate little if any lameness at the time of injury but an obvious swelling is always present. Lameness in these horses is typically reserved for the severe injuries which involve a tear of the distal check ligament.
Figure 5
Care for horses with this type of injury include forced rest, ice, topical anti-inflammatory medication (Surpass cream), platelet rich plasma injection (PRP), and extra-corporeal shockwave treatment. At a minimum, the horse needs to be stalled with hand walking only for 6-8 weeks followed by 6-8 weeks of a controlled rehab program. During this time, daily ice treatment is ideal. However, I have had patients that did not agree to the stall rest and were merely turned out for several months. These horses healed with a prominent thickness to the ligament but were sound and return to full work. In my experience, the combination of PRP injection followed by a series of shockwave treatment results in a smaller scar (thickening of the ligament). I have been involved in 2 cases that resulted in surgery to remove the distal check ligament. In one case, the ligament had been injected with cortisone which resulted in  abscessation of the ligament and in the second case, the injury was not allowed to heal properly before returning the horse to work!  Although these types of injury have a good prognosis for full return to work, the horse does need time off and I strongly recommend regular evaluations for soundness and follow-up ultrasound exam.

Friday, May 24, 2013

Testicular Enlargement in a Stallion

A 19 year-old stallion presented for the complaint of testicular enlargement. On physical exam, the left testes palpated firm, non-painful and was approximately 30-40% larger than the right testes (Figure 1). The potential differentials for an enlarged testes in a stallion include testicular neoplasia (cancer), hydrocele, scrotal hernia, testicular torsion, and orchitis. Definite diagnosis is based on ultrasound exam and histologic exam of the abnormal tissue. Ultrasound exam of the stallion's testes was performed during the initial visit.

Figure 1
In Figures 2 and 3, the left testes is imaged via ultrasound. The testicle appears to be divided by two tissues-types which vary in density or echogenicity (degrees of brightness). The normal tissue appears brighter or hyper-echogenic whereas the abnormal tissue appears darker or less echogenic. The edges of the abnormal tissue are distinct and there are multiple, small "stars" or areas of increased echogenicity throughout the abnormal tissue. 

Figure 2

Figure 3
Ultrasound exam of the right testes revealed a homogeneous tissue consistent with normal testicular structure (Figure 4). The echogenicity did NOT vary throughout the testicle and the over-all size of the testicle was less than the left testicle. In Figure 5, the left and right testicles were imaged simultaneously and the difference in testicular architecture becomes more clear when comparing the "normal" right tests to the "abnormal" left testes. 

Figure 4

Figure 5

Testicular neoplasia or cancer is relatively rare in stallions compared to dogs. The types of cancer include seminomas, sertoli cell tumors, and leydig cell tumors. Histopathologic exam is required to determine the type of testicular cancer. All three types of cancer will result in compromise of normal sperm-producing tissue and thus reduction in fertility. Seminomas are the most common of the three types of testicular cancer in stallions and may have a high degree of malignancy and invasiveness. Scrotal hernia, testicular torsion and orchitis are additional causes of testicular enlargement which are typically associated with varying degrees of pain and inflammation. Ultrasound findings of these conditions may include small intestinal loops, dilated vascular supply and pockets of purulent debris. Similar to testicular cancer, these conditions typically alter the conditions for normal sperm production and will reduce fertility. A more benign cause of testicular enlargement is known as a hydrocele. This corresponds to an accumulation of abdominal fluid within the scrotal sac. Although benign, the increase in fluid may cause change in temperature and pressure which will also affect sperm production. This condition is more easily confirmed with ultrasound exam alone!.

The stallion in this case is scheduled for surgical removal of the affected testes for definitive identification of the cause for the testicular enlargement. Stay tuned!! 

Friday, May 17, 2013

Injectable Supplements for Horses

Listed below are the most common (non-steroidal) injectable supplements administered to horses to treat for active arthritis and hopefully slow down the development of arthritis. These medications vary in cost, method of administration, and approved use. One of the best known and most commonly used is Adequan. The active ingredient in Adequan is polysulfated glucosaminoglycan (PSGAG) and is FDA approved for intra-muscular and intra-articular use in horses. It is reported that PSGAG-containing products, such as Adequan, work by reducing inflammatory mediators within the joint and help maintain healthy cartilage. Adequan may be given in a loading dose initially for 5-7 treatments and then once monthly or may be administered every 6 months as a loading dose of 7 treatments that are 4-7 days apart.
Figure 1: Molecular structure of Adequan

Figure 2: Intra-articular Adequan

Similar to Adequan , a relatively new supplement in the US is known as Pentosan. The active ingredient in Pentosan is Pentosan Polysulfate Sodium (PPS) and is distinct in molecular structure from Adequan (Figure 1 versus Figure 3) . In humans, PPS is used to treat bladder pain associated with cystitis. In addition, clinical research in humans suggests that PPS may reduce clinical signs associated with arthritis. In horses, clinical and empirical data indicates that regular administration of PPS-containing products reduces clinical signs associated with osteoarthritis. Pentosan is available in the United States as a generic product that is sold through compounding labs (Figure 4). In my practice, it is commonly administered as an intramuscular injection, initially as a loading dose (5 injections, 1 week apart) and then 1-2x per month.

Figure 3: Molecular structure of PPS

Figure 4: Generic Pentosan

A PPS containing product that is licensed for use in horses in the US and FDA approved is PentAssuie (Figure 5) . This product  contains both Pentosan AND N-acetyl glucosamine (PSGAG). N-acetyl glucosamine is a PSGAG but is slightly different in structure compared to Adequan. PentAussie is approved for post surgical lavage and is considered "off label" when administered intra-muscularly. 

Figure 5
The product known as Legend is an injectable supplement approved for use in horses that contains Hyaluronate sodium which is non-sulfated glycosaminoglycan. Hyaluronate is a normal constituent of joint fluid and plays a key role in regulating inflammation within the joint. The product Legend is typically administered intravenously however products containing hyaluronic acid are injected directly into the joint. The frequency of IV administration varies from prior to competition to monthly.  

Figure 6

 Polyglycan (Figure 7) is an injectable supplement that contains a mixture of several productions (Figure 8). It is approved for use in horses but NOT for intravenous administration, which is the most common route of treatment! The product contains hyaluronate, acetyl glucosamine, and chondroitin sulfate (active ingredient in Cosequin).  In my practice, this supplement is administered several days before competition and/or on a monthly basis.

Figure 7

Figure 8
Obviously there is much more information to consider when choosing one of the above for your horse. These are the general guidelines I strongly recommend:

1: Once a horse is old enough to begin training, I recommend an "injectable" supplement to be administered monthly for the duration of that horse's career. Injectable supplements are likely to be superior to oral supplements.
2: Generally speaking intra-muscular injections are less expensive and can be done at the barn by the owner/barn manager. As such, I recommend starting with one of these supplements which include Adequan, Pentosan, and PentAussie.
3: Polyglycan is a great product and should be considered as an "in-addition-to" supplement to be used in horses that are in heavy competition or suffering from advanced osteo-arthritis.
4: The money you spend on a monthly basis for these "injectable" supplements is likely to be the best long term investment you can make for your horse besides having a good farrier and competent veterinarian!! 

Friday, May 10, 2013

Cystic Calculi in a Horse

A teenage gelding presented for the complaint of increased urination (polyuria) and increased water intake (polydypsia). The increased urination had become a significant issue since it was happening at all times including when under saddle and showing. The physical exam was normal and a blood sample was collected for CBC and chemistry analysis. In addition, a free-catch (non-sterile) urine sample was collected during the exam. The CBC and chemistry results were normal suggesting that a primary problem of the kidneys may not have been the cause for the frequent urination. However, the urine sample contained traces of blood, moderate calcium crystals, and moderate white blood cells. These findings suggested an inflammatory process either in the urinary bladder or urethra. A endoscopic exam (cystoscopy) of the urinary bladder was performed. In Figure 1, the internal cavity of the urinary bladder is visualized. A pool of urine is present and a large, yellow object consistent with a urinary bladder stone (cystic calculi) is located in the center of the bladder. The surface of the bladder stone is rough and spiculated. In Figure 2, the inflammation caused by the abrasive stone can be visualized. 

Figure 1

Figure 2
In Figure 3, a pool of "debris" is noted surrounding the bladder stone. This debris is likely made up of calcium crystals, purulent matter (white blood cells), and some bacteria. The irritation caused by the bladder stone likely resulted in hemorrhage within the urinary bladder which is a great media for bacterial colonization! As such, chronic urinary bladder infection or cystitis is a common problem in these patients that will not resolve until the stone and debris is removed. A bladder stone this size can only be removed through a surgical procedure. There are two options regarding surgical approach: 1: bladder exploration via an abdominal incision or 2: through a urethrotomy within the perineum. The latter is performed in a standing horse and is limited to small bladder stones.

Figure 3

The cause of urinary bladder stones in horses is believed to be in part due to diet. Horses consuming diets high in calcium such as alfalfa and drinking water that has a high calcium content may be predisposed to developing urinary bladder stones. However, the condition is relatively rare when one considers how many horses are fed a pure alfalfa diet!  In addition, horses can develop stones in the bladder AND kidneys. These stones may travel and lodge within the ureters and the urethra. In my clinical experience, I have diagnosed urinary bladder stones in 2 geldings and 1 mare. In addition, I have diagnosed kidney and ureter stones in 2 geldings and 2 mares. If the stones obstruct the flow of urine from the kidneys into the urinary bladder they will ultimately result in compromise of kidney function. Common clinical signs include increased urination, increased water intake, recurrent low-grade colic, fever, blood in urine, and poor performance.

Friday, May 3, 2013

Arytenoid Chondritis in a Horse

A 12 year old quarter horse mare presented for a 2-3 month history of coughing and "wheezing". The mare had developed the symptoms some what suddenly and was responsive to systemic corticosteroids. As such, it was initially thought that the mare was developing signs of heaves or COPD (chronic obstructive pulmonary disease). Heaves is relatively common in the southeastern United States and is a chronic progressive condition that involves an allergic condition that affects the lungs and causes fibrosis and scarring.     At presentation, the client was interested in finding out for sure what was causing the coughing and wheezing. Re-breathing exam was essentially normal with no wheezing detected or coughing. The mare was currently being treated with corticosteroids and had been for the past 48 hours. The initial plan was to scope the mare and perform a bronchoalveolar lavage (BAL) to confirm the diagnosis of heaves. However, when the endoscope was passed to the point of the larynx, we discovered what was the true problem!

Figure 1
In Figure 1 and 2, the larynx of the horse in question appears grossly abnormal. In Figure 1, the horse is in between breaths and there is thin slit between the arytenoids which consists of her airway. In Figure 2, the mare is taking a deep breath and the full extend of her airway is probably the diameter of a sharpie pen! There is large linear ulcer that crosses the left arytenoid cartilage and the significant thickening of both left and right arytenoid cartilages suggest chronic inflammation. In Figure 3, a "normal" endoscopy demonstrates what the full extent of the airway should be during inspiration and what normal arytenoid cartilage should look like!

Figure 2

Figure 3

Arytenoid chondritis is a relatively common cause of coughing and nasal discharge in older horses. This mare was a bit on the young side to have developed this condition. The causative agent is not clear but it is believed to be a combination of chronic irritation that is made worse by bacterial infection. In my experience, I have diagnosed this problem in horses that were exposed to a chemical irritant in agriculture setting such as dairy farms and produce farms; however, I have not been able to determine what chemical is causing the problem. Unfortunately  once the condition becomes chronic and the arytenoids are permanently disfigured, the only viable option is to perform a permanent tracheotomy. Surprisingly  horses do very well with permanent tracheotomies as long as they do not go swimming!! Clinical signs will improve with systemic corticosteroids and throat spray however these treatments will NOT reverse the damage done!!  This case, once again, demonstrate the importance of an endoscopic exam EARLY in the disease process.