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Equine Cushing’s Disease
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.
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.
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.
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).
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.
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 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.
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 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.
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).
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
Tryon International Equestrian Center to Open Facility for Equine Evacuees in Path of Hurricane Irma
Mill Spring, NC -- In response to numerous requests, Tryon International Equestrian Center (TIEC) has announced they will open the facility for equine evacuees in the wake of Hurricane Irma to assist those in need of safe stabling outside of the storm path and predicted impact radius.
Four hundred stalls will be available for evacuees at TIEC at a discounted rate and will be offered for reservation on a first come, first serve basis. Johnson Horse Transportation, Inc. is helping to coordinate commercial shipments to the Carolinas region from South Florida.
On-site lodging will also be offered at a discounted rate for hurricane evacuees. RV spaces will also be available for reservation. On-site dining and supplies are available through The General Store and a variety of restaurants on property will be open throughout the duration of the week.
Shavings, hay, and feed are available for purchase on property through the Stabling office.
To reserve stalls at TIEC, please contact (828) 863-1005.
To coordinate commercial horse shipment and transportation, please contact Johnson Horse Transportation at (610) 488-7220.
For more information on Tryon International Equestrian Center (TIEC), please contact www.tryon.com.
Red Maple Toxicity
by Dr. Kathy Samley
Red maple leaves (Acer rubrum) are toxic to horses. The fresh leaves themselves are safe, but they become toxic after the leaves have wilted. The wilted leaves can remain toxic for up to 30 days. Red maple leave toxicity is common in the fall when the leaves begin to wilt and accumulate on the ground.
A 1000# horse will develop clinical signs after ingesting at least 1.5 lbs of wilted red maple leaves. A toxic component of red maple leaves damages the horse’s red blood cells. The red blood cells eventually become lysed, which causes the horse’s packed cell volume (percentage of red blood cells in the blood) to decrease rapidly as the red blood cells are destroyed. Hemoglobin, a component of red blood cells, is filtered out by the kidneys into the urine and causes the urine to turn a dark red color. Hemoglobin is damaging to kidneys, leading to acute renal failure. Common clinical signs of red maple toxicity in horses are depression, jaundice, fever, dark red urine, and colic.
A physical exam is important to assess the status of the horse. Bloodwork and urinalysis can be used to confirm the diagnosis as well as assess how far the toxicity has progressed. Horses with hemolytic anemia due to red maple toxicity have hemoglobinemia (red-tinged serum), as well as signs of hemoglobin in their urine. Bilirubin will be elevated in the blood due to the hemolysis. Kidney values (BUN and creatinine) are often elevated depending on the amount of renal compromise.
If you suspect your horse has ingested red maple leaves a veterinarian should be called as soon as possible. If in the acute phase, activated charcoal may be administered through a nasogastric tube in order to help absorb the toxins. In most cases, hospitalization is necessary as the horse usually requires close monitoring, IV fluids, and critical care. A blood transfusion is often necessary if the horse’s packed cell volume is extremely low. Intravenous fluids are important to diurese the kidneys if they are showing signs of damage from hemoglobin. Vitamin C, vitamin E, and selenium can help treat the oxidative damage from the toxins.
Prognosis is guarded to poor, as horses can develop many secondary complications including acute renal failure, colic, and laminitis. Hospitalization and intensive care provide the best possibility of recovery. Early diagnosis and treatment is critical.
Equine Kissing Spine
By Laura Wodzinski, DVM, cVMA
In horses, kissing spine, more formally known as overriding dorsal spinous processes (ORDSP), is a condition where the spacing between the dorsal spinous processes (DSP) in the horse’s back vertebrae are narrowed and there is associated back pain. Thoroughbreds are overrepresented in the breeds commonly affected. In a study performed by Dr. Tracy Turner, DVM, DACVS, DACVSMR, dressage horses were the most commonly affected discipline with eventing horses being second. There is speculation that the appearance of kissing spine in these horses could be due to overuse of the back during collection and lateral movements causing inflammation and pain at the sight of impingement.1 In this article, you will learn how kissing spine is typically diagnosed and the various treatment options available.
The diagnosis of kissing spine is made after a thorough lameness evaluation and lateral radiographs of the spine. It is important to note that the presence of kissing spine radiographically without clinical signs of back pain is not necessarily a concern, however the horse may be predisposed to back pain in the future.1 Clinical signs of back pain include resistance to digital pressure over the back and epaxial muscles. Signs of discomfort including ears pinned, tail switching, and/or kicking out often accompanies this resistance. The horse may travel with his head in the air with a stiff back or may have some difficultly bending to one side. The more severely affected horse may progress to rearing or bucking.
Radiographs of the dorsal spinous processes show a narrowed space between the vertebrae with sclerosis, or increased bone density due to bony remodeling, on the adjacent touching sides. The most common location for ORDSP is the caudal thoracic vertebrae, where the seat of the saddle sits, between T13-T18 vertebrae. 1 Other diagnostic modalities used are nuclear scintigraphy, more commonly known as a bone scan, where the affected spinous processes will have a greater radiopharmaceutical uptake.2 Thermography can also be used to identify kissing spine by displaying specific thermal heat patterns.1 This tool may help differentiate between kissing spine and other causes of back pain. 1
There are several treatment options for kissing spine from physiotherapy management to surgery. Exercises to stretch the back include walking and trotting in a “long and low” frame and adding in ground poles to encourage further stretching. Additionally, stretches that include lateral bending and stretching their neck to their knees can be helpful in opening up the DSP spaces. Proper saddle fit is essential to the continued comfort of a horse’s back. Mesotherapy is another treatment where a combination of anti-inflammatories and LRS solution is injected with multiple very small intradermal needles over the back and croup. 1 Extracorporeal shockwave therapy (ESWT) can be used over the dorsal spinous processes and epaxial musculature to promote healing in the region. ESWT is a non-invasive technique that sends shock waves to a specific area to promote blood flow, increase the production of natural healing factors, and increases blood vessel formation.3
Injections with corticosteroid between the affected dorsal spinous showed improvement in 55% of horses. 1 Several surgical procedures have been described to physically open up the space between the dorsal spinous processes. Dr. Coomer from Cotts Equine Hospital in the United Kingdom developed a method where the interspinous ligament, the ligament that connects the spinous processes to one another, is cut to increase the spacing between the vertebrae. 4 In his study, Coomer found that 89% of horses treated medically had initial resolution of back pain versus 95% of horse treated surgically. None of the surgical cases had a recurrence of clinical signs and radiographs following surgery revealed a significantly widened interspinous space. 4 Visit the New England Equine Facebook page to see images from a recent kissing spine case!
There are many causes of back pain in the horse. Kissing spine is easily seen with radiographs and can be treated in a variety of ways to improve the comfort of the horse.
1. Turner, Tracy A,. "Overriding Spinous Processes (“Kissing Spines”) in Horses: Diagnosis, Treatment, and Outcome in 212 Cases." WOUND & ORTHOPEDIC MANAGEMENT AAEP Proceedings 57 (2011)
2. DVM, Kenneth Marcella. "Kissing Spines in Veterinary Equine Patients: Easy to Diagnose, Complicated to Treat." Dvm360.com. N.p., 17 Dec. 2014. Web. 08 May 2017.
3."Extracorporeal Shockwave Therapy." Large Animal Hospital. N.p., n.d. Web. 08 May 2017.
4. Coomer RP, McKane SA, Smith N, et al. A controlled study evaluating a novel surgical treatment for kissing spines in standing sedated horses. Vet Surg 2012;41(7):890-897.
Roaring (laryngeal hemiplegia)
Dr. Kathy Samley, DVM
What is it?
Laryngeal hemiplegia, commonly called "roaring" is a disease of the upper airway in horses. The larynx is the opening to the trachea, and consists of several pieces of cartilage. The arytenoid cartilages open to allow air into the trachea, and close during swallowing to prevent food and liquid from getting into the trachea. Laryngeal hemiplegia occurs when there is degeneration of the nerve that innervates the muscles of the larynx, preventing the arytenoid cartilage from opening properly. This prevents proper airflow into the trachea and causes a noise heard during exercise. This decrease in airflow can also lead to exercise intolerance. Laryngeal hemiplegia usually only affects one arytenoid, with the left side affected in 95% of cases. The specific cause of the nerve degeneration is unknown but there are likely genetic and acquired components that contribute.
The two main signs of laryngeal hemiplegia are upper respiratory noise during exercise and poor performance. The severity of laryngeal hemiplegia is graded on a scale of 1-4, with 4 being complete paralysis of the arytenoid. The volume and severity of the upper respiratory noise and the amount of exercise intolerance can vary based on the grade of the laryngeal hemiplegia.
Laryngeal hemiplegia is diagnosed through upper airway endoscopy. A small camera is passed up the horse's nares to the level of the larynx. The arytenoid cartilages are examined through several respiratory cycles to assess their movement. The horse cannot be sedated for this procedure, as sedation makes it difficult to properly assess arytenoid function. There are several other conditions that can cause upper respiratory noise in horses, so the larynx and surrounding structures are closely examined for any abnormalities. After a baseline examination, a post-exercise endoscope exam is often performed. The horse is exercised for several minutes and the scope is passed again to assess the function of the arytenoids immediately after vigorous exercise.
Laryngeal hemiplegia is typically a surgical condition and is corrected via a prosthetic laryngoplasty, "tieback," procedure. Two strong sutures are placed through the arytenoid cartilage and attached to one of the other laryngeal cartilages. The sutures help to abduct the arytenoid cartilage, opening up the airway. The laryngeal saccule is removed in order to further stabilize the tieback and decrease upper airway noise. This procedure has a good prognosis for return to athletic function. Additionally, horses with lower grades of laryngeal hemiplegia have shown improvement after several treatments of electroacupuncture.
These images show a before (left) and after (right) a tieback procedure. The left image is from a horse with grade 4 left laryngeal hemiplegia. Note how the left arytenoid cartilage is deviated to the center of the larynx, partially obstructing the trachea. After surgery, the left arytenoid is held open which allows normal airflow.