Sub-solar Abscess in a Horse!!

Figure 1

The radiograph in Figure 1 is of a horse's hind foot. This gelding has been suffering from chronic laminitis/founder for over 1 year. When I first examined this horse, there was nearly zero sole depth between the coffin bone and the bottom of the foot. In addition, the coffin bone was reduced in size due to gradual degradation (pedal osteitis) of the coffin bone. The pedal osteitis developed due to the chronic pedal bone rotation that is evident in Figure 2 (non-parallel red lines). It was decided that a deep digital flexor tenotomy combined with appropriate shoeing may help stabilize the foot and promote sole growth. Over 4-6 months after the surgery, the gelding's sole depth increased significantly, indicating normal hoof growth and he was more comfortable on this limb.

Figure 2

Recently, the gelding's lameness worsened and he was non-weight bearing when examined. A lateral radiograph was performed (Figure 1-3). A large, radiolucent area (red circle) was noted in the toe region of the foot with a track that appeared to be traveling toward the coronary band (Figure 3). These findings are consistent with a large, sub-solar abscess! 

Figure 3

The shoe was removed and a large "hole" was noted at the apex of the frog that extended into a cavity with the circumference of a golf ball! The abscess appeared to be draining however it involved a significant amount of space between the bottom of the sole and the coffin bone. After removing the shoe, the foot was soaked in a warm epsom salt solution and then was "packed" with a strong disinfectant. The gelding's lameness improved within 24 hrs however he remains lame at the walk. His return to soundness will take some time and most likely require a specialized shoe known as a hospital plate. Recurrent foot abscess formation is a common problem among chronically foundered horses and highlights the importance of regular trimming/shoeing plus radiographic examination!

Figure 4

Habronemiasis (Summer Sore) in a Horse!

The images in Figure 1-3 are from a horse that presented for a large, painful swelling along the mare's ventral abdomen. The mare had been treated by the referring veterinarian with anti-inflammatory medication and oral antibiotics with minimal improvement. A core biopsy revealed chronic inflammation with no specific cause identified and an ultrasound exam merely revealed diffuse edema. Close examination of the swelling (Figures 2-3) noted yellow granules which were consistent with sulfur granules. This finding is consistent with 2 diseases in horses which are cutaneous pythiosis and cutaneous habronemiasis. Identifying which pathogen is causing the lesions can be tricky and involves skin biopsies with special staining for pythiosis.

Figure 1

Figure 2

Figure 3

According to the Merck Veterinary Manual, "cutaneous habronemiasis or summer sores are a result of fly larvae which enter existing wounds or moist skin and migrate into the tissue causing irritation and a chronic granulomatous reaction".  As such, management of this condition involves fly control, medication for encysted larvae, AND medication for inflammatory reaction. Fly control is an ongoing issue at most farms and becomes increasingly important as the warm, summer months approach. The most common method for treating for the encysted larvae is a simple dose of oral ivermectin. Unfortunately, this is were most horse owners stop with treating summer sores. There are a multitude of topical therapies which include varying amounts of ivermectin and antibiotics. Unfortunately, these topical therapies are NOT appropriate for treating the chronic inflammatory reaction. As a result, many summer sores continue to increase in size and result in horrible wounds as imaged in Figures 4 and 5. These represent the MOST common location for summer sores in horses that being the lower limbs.

Figure 5

Figure 4

The large swollen plaque across the ventral abdomen is a uncommon location for a summer sore as is the upper lip noted in Figure 5. However, these lesions can develop on any part of the horse's body that is accessible by a fly!! It is critical that the horse owner understands that the chronic, inflammatory reaction is a result of a hypersensitivity or allergic reaction to the encysted larvae, before and AFTER it has been effectively killed with systemic ivermectin. As such, the horse must be treated for the hypersensitivity with products that contain immune suppressive doses of corticosteroids. In small, focal cases, the lesions are effectively treated with topical treatment however large summer sores will need systemic corticosteroid administration!! In my experience, this is the ONLY way to effectively rid the horse of this condition. Unfortunately, once a horse develops summer sores, they will be predisposed the following fly season to re-develop sores in the same regions. I have developed a highly effective topical cream with the help of a pharmacy and would be happy to dispense this product to owners of horses that are dealing with this highly annoying condition!!

Figure 6

Paranasal Sinus Cyst in a Horse

Figure 1A

Figure 1B

The radiographs in Figure 1-3 correspond to a horse that presented for chronic nasal discharge. The discharge was bilateral and there was a reduction in the air flow through the nasal passages. Due to the reduced airflow, it was decided to first radiograph the gelding's skull and then potentially scope the upper airway.

Figure 2A

Figure 2B

Radiographic exam revealed a soft tissue mass that was located in the maxillary sinus. In Figures 1-2 A and B the soft tissue mass appears as a round, white structure that is highlighted by the red dotted circles. In Figure 3 there appears to be a soft tissue mass in both the left and right maxillary sinus (red dotted circles). The mass appears larger on the left side of the skull.
The gelding was NOT sedated for endoscopic exam in order to reduce the likelihood of respiratory distress.

Figure 3

 In Figure 4, an endoscopic image reveals a smooth, soft tissue tumor/mass that is obstructing the nasal passage. Moderate amounts of purulent debris can be seen accumulating around the soft tissue mass. Based on the endoscopic and radiographic findings, the gelding was referred for surgical exploration. At surgery, a large paranasal cyst was exposed in the left maxillary sinus and a small cyst was identified in the right maxillary sinus. Both cysts were removed and the gelding recovered uneventfully. It is likely that the cysts began to develop early in life for this gelding and did not become clinically relevant until they grew into the nasal passages. Once they are removed via surgical intervention the prognosis is very good !!

Figure 4

Shoulder swelling in a Horse

The mare in Figure 1 presented for a complaint of sudden onset severe swelling at the point of the right shoulder and near non-weight bearing lameness of the same limb. The mare is normally kept with other horses and there is no history of a "equine dispute" or evidence of external trauma. On presentation, the swelling consists of significant edema and the mare is considerably "tender" to pressure and palpation of the swelling. Manipulation of the limb was limited due to the significant pain response that resulted. Radiographic exam of the horse's shoulder is a viable option however due to the pain on manipulation and significant soft tissue swelling, an ultrasound exam was more highly indicated.

Figure 1

The images in Figure 2 and 3 correspond to the soft tissue swelling noted in Figure 1. A large, fluid filled pocket was noted deep to the skin surface. The fluid had a mixed pattern of echogenicity suggesting that the fluid consisted of cellular debris mixed with blood/serum. These findings are most consistent with a large subcutaneous abscess. The two most likely causes for abscess formation in this area would be trauma induced or abscess formation from a bacteria called corynebacterium pseudotuberculosis. This condition is also known as "Pigeon's fever". Pigeon's fever is a serious condition due to the highly infectious nature of the bacteria AND the fact that once the bacteria is present on the premises, it is very difficult to remove from the environment. Correct diagnosis depends on collecting a sample of fluid from the abscess and submitting for laboratory evaluation. Treatment of either condition requires establishing drainage of the abscess and daily  lavage for 10-14 days after drainage. Microbiological identification in this case is pending and the horse is in quarantine on the farm! The abscess was opened and drainage established.

Figure 2

Figure 3

Interestingly, within 7 days of examining the mare above, a gelding presented for similar symptoms. He was found non-weight bearing lame in the pasture with severe swelling of the shoulder region. The referring veterinarian provided digital radiographs which did not identify the cause of the lameness/swelling. On ultrasound exam, a bright, bone-like structure (red dotted line) was noted extending into a fluid filled mass that appeared to be a hematoma (Figure 4 and 5). The bone-like structure was the humerus bone (red dotted line) and it was fractured plus displaced. This gelding was humanely  immediately euthanized!

Figure 4

Figure 5

Although these cases are quite different in outcome, they demonstrate the benefit of soft tissue ultrasound with regards to assessing "swellings". As demonstrated it is possible to evaluate soft tissue changes as well as bony changes.

Superficial digital Flexor Tendonitis (Bowed tendon) in a Horse!

A  twenty year-old mare presented for sudden, severe swelling of the left front lower limb. The mare was nearly non-weight bearing lame and had been seen galloping around her paddock moments before. Prior to my exam, the mare was stalled for 7 days and treated with ice and systemic non-steroidal mediation (phenylbutazone). On presentation there was a noticeable "profile" to the lower portion of the forelimb (Red line:Figure 1). The mare was moderately positive to pressure over this swelling and was lame at the walk. On palpation, there was no distinction between the superficial digital flexor tendon and the deep digital flexor tendon.

Figure 1

Ultrasound examination of the lower limb, beginning just below the knee (carpus) revealed inflammation of the superficial digital flexor tendon (SDF). The inflammation was moderate just below the knee (Figure 2) however became severe further down the leg (Figure 5). In Figures 2 and 3, moderate to severe edema (dark tissue) is noted with pockets of disrupted fiber pattern. The image in Figure 4 is of the opposite limb for comparison to /the abnormal limb. In Figure 5, the SDF tendon (Red arrows) is severely enlarged and there is no apparent pattern with regards to the fiber pattern. These findings are consistent with a near rupture of the SDF tendon.

Figure 2

Figure 3

Figure 4

Figure 5

Although the outward and inward findings are severe, the prognosis for pasture soundness is good. It will take 6-12 months for this type of injury to heal with a fibrotic scar but the mare is likely to return to soundness as a pasture horse. Unfortunately, her prognosis as a riding horse is poor and it is not recommended to return this mare to any type of forced work due to her age and degree of injury. Tendonitis of the superficial flexor tendon can occur in various regions of the lower limb. The closer to the knee/carpus (High bow), the worst the prognosis, even for pasture soundness. This is due to the constant irritation of the tendon when the horse advances the limb. In addition, horses that suffer a "bowed" SDF tendon are at increased risk for another injury to the same tendon and it commonly occurs above or below the original injury. My recommendation for rehabilitative care includes the following:

1: Limited activity: preferred stall rest with hand walking for 2 months followed by small paddock turn-out
2: Daily ice therapy for 2-3 weeks
3: Topical non-steroidal cream: Surpass
4: Consider Extra-corporeal shockwave treatment and PRP injection.

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.

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!! 

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!! 

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.

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.