EquineSite.com

Dr. Taylor Mahren
New England Equine Medical and Surgical Center
15 members way
Dover NH 03820
603-749-9111

OSTEOCHONDROSIS:

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Osteochondrosis (OC) is a developmental disorder that leads to failure of bone and cartilage formation (endochondral ossification). Failure of normal bone and cartilage formation results in irregularities in the thickness of cartilage at joint surfaces. This creates areas of weakness and affects the nutrition of the deeper layers of  cartilage and bone and can lead to necrosis (decay). Biomechanical influences, mainly shearing forces, lead to the formation of fissures (tiny fractures) and produce cartilage flaps, or detachment of cartilage or fragments of cartilage and bone. 

DIAGNOSIS:

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The typical OC patient is a yearling with effusion (swelling) of the upper hock joint or stifle joint.  The horse is typically not lame, and radiographs reveal a fragment on part of the tibia called the distal intermediate ridge of the tibia or irregularities of the femur at what is called the lateral trochlear ridge. However, there are many variations on this scenario and age, lameness, effusion, and the joint affected can vary. Most OC patients are juvenile with the most severe cases being seen in foals as young as 6 months of age. OC can also only manifest itself when the horse is put into training and the joint becomes challenged by activity which varies with discipline. Radiography is the gold standard for diagnosing OC but it is not capable of detecting subtle lesions. 

DISTRIBUTION OF LESIONS:

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OC is most commonly diagnosed in the tarsus (hock), femoropatellar joint (stifle), and the fetlock, but it has been described in almost every synovial joint.     

CAUSE OF THE DISORDER (PATHOGENESIS):

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OC is a complex disease and multiple factors are involved in the progression and development of the disorder. Biomechanical influences, exercise, failure of vascularization, nutrition imbalances, and genetics have all been linked to the disease. 

TREATMENT:

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Treatment of lesions depends on size, clinical signs, location, and severity. Small OC lesions in very young horses where there is still good capacity for regeneration or in very mild OC cases,  nonsurgical management consisting of  rest, controlled exercise, systemic anti-inflammatories, and intra-articular (within the joint) medications can be successful. Surgical management is the treatment of choice in most cases.  This involves removal and debridement of the fragments from the joint via a small incision and use of an arthroscope (surgical instrument with camera). 

PROGNOSIS:

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The prognosis after surgical intervention varies among joints and the severity of the lesion. However, prognosis for return to athletic activity is fair to good for the majority of joints involved. 

TAKE HOME:

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Things to consider when trying to prevent osteochondrosis would be to avoid feeding high energy feeds to growing animals which can lead to excessive rapid growth and secondary osteochondrosis development. Breeders should monitor sires and mares suspect of yielding offspring with osteochondrosis. Any young horse with persistent joint effusion should be evaluated with radiography. Horses with OCD that are identified and treated early may be athletic; however , if left unrecognized osteoarthritis (degenerative joint changes) and lameness can develop. 

SUBCHONDRAL BONE CYSTS:

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Subchondral bone cysts, also known as subchondral cystic lesions (SCLs), are a serious cause of lameness and difficult to treat. They are characterized by radiolucent (darker than normal) areas of bone often accompanied by sclerosis (boney remodeling) at a joint surface. In the past, they were considered to be part of the osteochondrosis complex, however, the location of OC lesions differs from SCLs. SCLs are found underneath the cartilage in a weight-bearing area of the joint. 

CAUSE OF THE DISORDER (PATHOGENESIS):

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Many mechanisms have been proposed for the development of SCLs. However, only two hypotheses have been supported experimentally. The first hypothesis is based on the hydraulic theory in which there is primary cartilage damage followed by secondary intrusion of synovial fluid. The fluid is thought to place mechanical pressure on the subchondral bone through its hydraulic action during weight bearing, resulting in necrosis of the subchondral bone plate. The second hypothesis is the inflammatory theory in which various inflammatory mediators become upregulated (increased) leading to the development of cysts. 

DISTRIBUTION OF LESIONS:

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SCLs occur mainly in the stifle (medial femoral condyle) and the phalanges (fetlock, pastern, coffin bone, and navicular bone) and less commonly in the carpus (knee), cannon bones,  tibia, radius, talus (hock), proximal sesamoid bones, humerus, patella, scapula, and mandible. 62 % of lesions occur in males and Thoroughbreds represent the majority of affected animals. 

CLINICAL SIGNS:

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Horses often present with lameness in the affected limb with or without joint effusion (swelling). SCLs occur mostly in young horses between the ages of 1 and three years and lameness commonly occurs at the onset of training. 

DIAGNOSIS:

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Diagnosis is made via lameness examinations and radiographs. In rare cases, computed tomography, CT, has been of great value when SCLs cannot be visualized radiographically. 

MANAGEMENT:

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Nonsurgical management of SCLs involves rest and the use of non-steroidal anti-inflammatory drugs; however, success rate is variable. Intralesional corticosteroid injections do have better success rates but this is generally performed under arthroscopic guidance under general anesthesia. Surgical management is the treatment of choice and involves debridement of the cyst and a combination of intralesional corticosteroid injection, bone grafts, and other modalities. 

PROGNOSIS:

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The healing of treated SCL normally is slow and can take several months to years if just surgical debridement is used, but the use of bone replacements and growth factors to enhance bone healing shortens the healing time considerably. Younger horses have a better prognosis for complete recovery compared to older horses. If the SCLs are associated with osteoarthritis in older patients a cautious prognosis is given. 

REFERENCES:

1.) Auer and Stick. Equine Surgery, 4th edition. Chapters 88 and 89. 

Katy Raynor, DVM

www.newenglandequine.com

Equine injuries can be just as common whether your horse is stalled or turned out to pasture. The best way to treat any injury, however, is to be prepared with a well-stocked, easily accessible first aid kit. In fact, keeping even a few of the below first aid essentials could help save a severely injured horse's life while you wait for your veterinarian to arrive. 

Vital first aid supplies

Every horse owner needs a few basic first aid essentials. These items will help you dress wounds, reduce swelling and inflammation until your veterinarian arrives. Depending on your preference, pre-made first aid kits are available at our clinic. Or, you can make your own kit with the following items: 

• Bandages - protect wounds, support muscles, and hold ice packs with horse leg wraps or self-adhesive bandages.
• Blunt-Tipped Scissors - safely cut away and remove bandages and wraps.
• Buckets - soak hooves and more with a few buckets kept specifically for first aid use.
• Flashlight/Head lamp - view wounds and injuries in darkness or poor light conditions.
• Hoof Pick
• Ice Packs - prevent and reduce swelling.
• Rubbing Alcohol - used as a disinfectant as well as good for cooling horses rapidly if febrile.
• Sheet or Roll Cotton - help apply pressure bandages or offer support to injured muscles or bones.
• Sterile Gauze - clean and cover minor cuts and wounds with sterile gauze or Telfa (non-stick) pads of various sizes. Use gauze rolls to hold dressings and pressure wraps in place.
• Exam Gloves- keep your hands clean and help prevent wound contamination.
• Thermometer - measure your horse's temperature (normal range is 99.0°F to 101.5°F) whenever you have a concern before you call the vet. EVERY FARM SHOULD HAVE ATLEAST 1 WORKING THERMOMETER!
• Stethoscope- Know how to take your horses heart rate! Great information to help your vet!
• Wound Antiseptic
• Wound Cleaner

Easy access to your veterinarian's and farrier's contact information is also vital. In addition, a complete record of all your horse's medications, vaccinations, and wormers is essential - especially in an emergency. 

Helpful first aid extras

The best first aid kit holds a range of products to deal with a wide variety of injuries or accidents. In addition to the basics, however, having the following products accessible will help you further prepare for almost any mishap: 

• Electrolytes
• Probiotics- (good quality)
• Eye Cleanser/Saline
• Hoof Boot
• nSAIDS (phenylbutazone, banamine, Equioxx) - Only used after consulting a veterinarian Always take temperature before administration.
• Poultice
• Trailering and Barn additional tip!

Always have a fire extinguisher available in your barn and trailer/truck at all times!

by Dr. Kathy Samley

New England Equine Medical & Surgical Center

What is Equine Cushing’s Disease?

Have you ever noticed a horse with a long curly hair that does not shed out in spring? This may be an early sign of Equine Cushing’s Disease. Pituitary pars intermedia dysfunction, often referred to as Equine Cushing’s Disease, is a common disorder in older horses and ponies. Research shows that it can occur in up to 25% of aged horses. The typical age of a horse diagnosed with PPID is 18-23 years. Early diagnosis is often difficult, but can lead to a better prognosis for treatment. The most common, and often earliest, clinical sign is an abnormal haircoat that does not shed out in the spring. 

What causes Equine Cushing's Disease?

This endocrine disease begins with a deficiency of dopamine within the brain. This deficiency is caused by degenertion of dopamine-producing neurons in the brain and is similar to the disease process that occurs in human Parkinson’s disease. In normal horses, dopamine acts to inhibit the pars intermedia of the pituitary gland. Without dopaminine's inhibitory effect, the pituitary gland englarges and begins producing an overabundance of hormones. These hormones affect many different body systems, including causing the adrenal gland to overproduce its own hormone: cortisol. PPID is slowly progressive, and may occur in up to 25% of aged horses. 

Common clinical signs

Besides an abnormal haircoat, other common clinical signs of PPID include weight loss and/or muscle wasting, abnormal distribution of body fat, lethargy and hyperhidrosis (excessive sweating). The excessive production of cortisol can often lead to chronic laminitis. Depending on the progression of the disease, the laminitis can become severe and life-threatening. Chronic laminitis often appears externally as divergent rings in the hoof capsule. Since cortisol is immunosuppressive, horses with PPID are more prone to chronic or recurrent infections. If you notice any of these clinical signs, you may consider getting your horse tested for PPID. 

Testing

There are several different tests that can be performed to diagnose PPID. All of these tests involve drawing at least one blood sample from the horse and measuring the levels of various hormones in the bloodstream. The two most commonly used tests are baseline ACTH and the TRH stimulation test. All horses with suspected Cushing’s disease should have their insulin levels evaluated as well because insulin resistance is commonly associated with PPID.  

Treatment

The drug pergolide (Prascend) is the treatment of choice for PPID. This drug works by mimicking the action of dopamine in the brain, which inhibits the pituitary gland and prevents the overproduction of pituitary hormones. In addition to pergolide treatment, proper management and nutrition is important for treating horses with PPID. Since PPID horses are at risk for developing insulin resistance, they should be fed a diet that is low in soluble carbohydrates. This can include a complete feed, such as a senior feed, that is high in fiber but low in starch. Grazing should be limited due to the high carbohydrate content of lush pasture. PPID horses should have dentals performed twice a year, and should have regular fecal floats performed in order to develop an appropriate deworming program. Proper trimming/shoeing is vital for managing horses with chronic laminitis due to PPID.  

Prognosis

With pergolide treatment and proper management, horses with PPID can live many years with a good quality of life. Pergolide is a life-long treatment for affected horses, and often the dose will need to be increased in order to continue controlling the signs of the disease. Early diagnosis and treatment can improve the prognosis. Good management practices are equally as important as pergolide in maintaining a good quality of life for horses with PPID.

by Dr. Jacqueline Jewell, New England Equine Medical & Surgical Center

Nephrosplenic entrapment, also known as left dorsal displacement, is a type of colic that occurs when the left large colon gets entrapped over the nephrosplenic ligament.  The nephrosplenic ligament connects the left kidney to the spleen in the horse.  Of the horses that present for colic, approximately 2.5-9% are diagnosed with nephrosplenic entrapment (Nelson et al., 2016).

Etiology (cause)

It is not clear what the direct cause of nephrosplenic entrapment is. It is hypothesized or suspected that it is a result of colonic motility dysfunction or an accumulation of gas, which allows the large colon to move between the spleen and body wall. The colon then entraps over the nephrosplenic ligament after further dorsal displacement.

Signalment (age, breed, sex)

Occurs most commonly in older geldings.

Clinical Signs

Mild to moderate abdominal pain (colic) can occur.  Signs can include crouching, leaning to the left, or a desire to go down.  Nasogastric reflux (more fluid comes out of the stomach than is pumped into it by nasogastric tube) may be obtained if the colon places pressure on the duodenum (the first portion of the small intestine).  Tympanitic sounds can sometimes be heard on auscultation.

Diagnosis

Diagnosis is usually made through a combination of different diagnostics.  Rectal palpation is one of the primary diagnostics used in the diagnosis of nephrosplenic entrapment.  A gas distended left colon, palpation of the colon in the nephrosplenic space, and the left ventral colon lying dorsal to the left dorsal colon are all findings that support the diagnosis of nephrosplenic entrapment.

(The Glass Horse)

Left colon in the nephrosplenic space over the nephrosplenic ligament

(The Glass Horse) 

Normal anatomy of the nephrosplenic space and renosplenic (nephrosplenic) ligament

Transabdominal ultrasonography (ultrasound of the abdomen) is another diagnostic that is commonly used in the diagnosis of nephrosplenic entrapment. On ultrasound, the view of the left kidney will often be obstructed due to a gas filled colon. Being unable to visualize the left kidney is not definitive in the diagnosis of this condition. The dorsal aspect of the spleen can be ventrally displaced. The view of the dorsal aspect of the spleen can also be obliterated by gas echogenicity.

(Orsini and Divers, 2014)

Other diagnostics used include bloodwork, such as complete blood count (CBC), chemistry, packed cell volume (PCV), and total protein (TP). Bloodwork with nephrosplenic entrapment is usually normal, but mild dehydration can be seen.

Abdominocentesis, a technique where fluid is collected from the abdominal cavity using a needle, usually reveals normal abdominal fluid.  The fluid may contain blood from the spleen, since the spleen is usually located more ventrally.

Treatment

Non surgical

Non-surgical treatment can consist of administration of intravenous fluids, sedatives and analgesics, administration of phenylephrine followed by exercise, and rolling under general anesthesia.

An intravenous catheter is often placed to facilitate administration of intravenous fluids, sedatives, analgesics, and phenylephrine. Intravenous fluids are given to maintain hydration and correct any dehydration. Sedatives and analgesics (drugs for pain control) can be used for mild to moderate and severe pain.  Xylazine, with or without Butorphanol, and flunixin (Banamine) are often used for mild to moderate pain. Detomidine is often used for more severe pain. Xylazine is a short-acting alpha-2 agonist drug that provides both sedation and analgesia.  Butorphanol is an opioid drug used as an analgesic. Flunixin is a non-steroidal anti-inflammatory drug used to decrease pain and inflammation. Detomidine is also an alpha-2 agonist drug, but is longer acting than Xylazine.

Phenylephrine is often administered and is followed by lunging. Phenylephrine is a medication that works by constricting blood vessels. This causes the spleen to contract, which helps to dislodge the colon from the nephrosplenic space. The dose usually given is 10-20 mg in 1 L of saline at a slow rate (3 micrograms/kg/min) over 15 minutes. This is followed by approximately 20 minutes of lunging to aid in dislodging the colon from its entrapment. After lunging, rectal and ultrasound exams are repeated to see if the colon has dislodged.

If the colon has not gone back to the correct position, a rolling procedure can be performed under general anesthesia. The horse is dropped on its right side, so the left colon that is entrapped is uppermost. The horse is then rolled into dorsal recumbency (on its back), then on its left side. The horse can be palpated per rectum while recumbent (down) to see if the entrapment is resolved.  Ultrasound can also be repeated following the rolling procedure. The rolling procedure can be repeated if the entrapment does not resolve, or the horse can be taken to surgery.

Surgical

Surgical treatment may be indicated if nonsurgical treatment is unsuccessful, or the horse is unresponsive to analgesics and sedatives. Other indications for surgery can include presence of nasogastric reflux, colic of long duration, and abdominal distention.

Methods of surgical treatment include ventral midline celiotomy, standing flank laparotomy, and standing laparoscopy. A ventral midline celiotomy (abdominal exploratory surgery) is performed under general anesthesia. It helps to ensure a successful correction and allows opportunity to evaluate overall intestinal health.  A standing flank laparotomy (incision into flank) is performed with sedation and avoids general anesthesia. Avoiding general anesthesia helps to reduce the recovery time. This approach provides direct access to entrapment when performed on the left.  Standing laparoscopy is not commonly performed, but typically involves three small incisions, one for the laparascope (camera) and two other portals for instruments.

Prevention

Nephrosplenic space ablation (surgical closure of the nephrosplenic space) helps to prevent recurrence. This can be performed by standing flank laparotomy, but is usually performed by standing laparoscopy and typically is performed in horses with previous nephrosplenic entrapment events. Methods of laparscopic closure have included suturing the space closed, using mesh, and barbed suture. Other surgical methods of prevention include large colon colopexy (attaching the large colon to the body wall) and large colon resection (removing a portion of large colon).

References

Farstvedt E, Hendrickson D. Laparoscopic Closure of the Nephrosplenic Space for Prevention of Recurrent Nephrosplenic Entrapment of the Ascending Colon. Veterinary Surgery, 2005; 34: 642-645. DOI:10.1111/j.1532-950X.2005.00099.

Fogle, C. NCSU CVM Equine Medicine and Surgery Course Notes, Spring 2015. Equine Colic Lectures.

Gandini M, Nannarone S, Giusto G, Pepe M, Comino F, Caramello V, Gialletti R. Laparoscopic nephrosplenic space ablation with barbed suture in eight horses. JAVMA, 2017; 250(4): 431-436.

Nelson BB, Ruple-Czerniak AA, Hendrickson DA, Hackett ES. Laparoscopic Closure of the Nephrosplenic Space in Horses with Nephrosplenic Colonic Entrapment: Factors Associated with Survival and Colic Recurrence. Veterinary Surgery, 2016; 45: O60-O69. DOI:10.1111/vsu.12549.

Orsini JA, Divers TJ, eds. Equine Emergencies: Treatment and Procedures. 4th ed. St. Louis, MO: Elsevier; 2014.

The Glass Horse