Severe Navicular Disease in a Horse

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.A 10 year-old thoroughbred gelding presented to PHD veterinary services for the complaint of intermittent forelimb lameness. The gelding was purchased several months following a prepurchase exam performed by a local veterinarian. The buyer opted for NO radiographs at the time of the prepurchase considering that the horse was sound. Unfortunately, within several months after purchase, the gelding developed a lameness in the right front foot which was intermittent. The client contacted  PHD veterinary services for foot radiographs and a lameness exam. The lameness exam noted NO lameness in the forelimbs but rather a mild to moderate lameness in both hind limbs after flexing the upper limbs (hocks/stifles). The gelding was not positive to hoof testers in either forelimb. A radiographic exam was elected to document the palmar angle and sole thickness in both front feet. The image in Figure 1 is a lateral image of the right front foot and Figure 2 is a lateral image of the left front foot. The yellow arrows are highlighting the navicular bone of each foot.

Figure 1

Figure 2

Interestingly, the lateral image of the suspect foot (right front) appeared normal however the lateral radiograph of the left front foot was highly abnormal. The navicular bone of the left front foot was flattened and completely sclerotic when compared to the navicular bone of the right front.foot. Additional views of the navicular bone are imaged in Figures 3 and 4.  In Figure 3, the skyline projection of the navicular bone suggests severe deterioration of the bone and what appears to be a chronic fracture of the navicular bone (yellow arrow). The flexor surface of the navicular bone is very irregular.

Figure 3

In Figure 4, the distal border of the navicular bone is imaged. The yellow dotted line outlines the navicular bone and the yellow arrows are pointing to the many dark circles which are consistent with areas of lysis and/or cyst formation. The findings in Figures 3 and 4 are consistent with SEVERE degeneration and likely chronic fracture of the navicular bone. 

Figure4

These findings are NOT consistent with the physical exam findings of a sound horse or the history unless this horse has had the nerves, which provide innervation to the foot, surgically transected (nerved). At the time of the exam, the gelding did demonstrate sensation to the skin along the heel bulbs however there were small scars consistent with a previous surgery over the neuro-vascular bundles. Considering how normal the right front navicular bone appears, the degeneration of the left front navicular bone is most likely due to a septic process from a penetrating foreign body that resulted in infection of the navicular bone or a traumatic fracture. Regardless of the cause, these radiographic findings are suffice to retire this horse from forced exercise and hope that he remains comfortable for an extended period of time. This case represents another example of the benefit of simple foot radiographs as part of all prepurchase exam.

Wood Splinter Foreing Body in a Horse

A young mare presented with a baseball-size swelling on the left side of her neck that was just below the jugular groove. Two weeks prior, the mare presented with a puncture wound in the same area and the referring veterinarian removed several splinters. The mare was treated with antibiotics and the wound healed slowly; however, purulent discharge developed recently and the mare was tender to manipulation of the swelling. An ultrasound exam was performed and several linear foreign bodies (yellow arrows) were noted (Figures 1-3).

Figure 1

The linear foreign bodies were approximately 1-2 cm deep in the tissue and ranged in length from 5mm to 20mm (yellow arrows). Most concerning was the close proximity of one linear foreign body with the carotid artery (red circle in Figure 1)!!

Figure 2

Figure 3

 A 6cm incision was made directly over the linear foreign bodies followed by careful dissection of the subcutaneous tissues (Figures 4 and 5). Although the ultrasound exam suggested that the foreign bodies were big and obvious, it was quite tedious to locate the wooden offenders. In this case, 2 weeks had passed since the mare had impaled herself and her body had begun the process of forming thick scar tissue around the splinters, like a cocoon. After what seemed hours, 5 wooden splinters (Figure 6) ranging in size were removed from the mare's neck!!

Figure 4

The wound was lavaged heavily and left open to heal by second intention. It is probable that some wood fragments remain within the wound however their size and the extensive surgical exposure should allow for adequate healing without complications.

Figure 5

Figure 6

Rattle box (Crotalaria spp) in full bloom in Florida!!

The images below (Figure 1-2)  are of a plant known as "Rattle box". This plant is commonly found throughout Florida and the southeastern USA however is usually only found to be blooming during the spring and fall months (Figure 3) . There are several varieties of this plant that are all in the Crotalaria spp family. The plant produces a toxin known as a pyrrolizidine alkaloid which causes pulmonary hypertension and liver fibrosis. Interestingly, horses develop a taste for these plants and will consume them during the months that they are present in the pasture; however, clinical signs typically don't develop for 2-4 months.

Figure 1

Figure 2

Figure 3

The effect that the toxin has on horse's liver is remarkable. In the image below, there is a normal sample of liver (top) next to a fibrotic sample of liver (below). The fibrosis is so severe that there is minimal blood filtration through the liver, rendering the liver useless. As such, toxins that are normally detoxified by the liver accumulate within the horse and result in depression, anorexia, neurologic disease and ultimately death!  Once the horse develops clinical signs for liver fibrosis, the prognosis is very poor. It is strongly recommend that all pastures and fence lines be screened for the presence of this plant species, especially during the fall and spring ( that means now!!). The plant must be removed by physically pulling the plant out of the ground. Mowing will only spread the plant by disseminating the seeds that are present within the "rattle box" pods!! If your horse has been exposed to this plant, I would recommend a simple chemistry analysis of their blood to determine if they have early signs of liver disease.

Figure4

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.

Guttural Pouch Mycosis in a horse!!

The endoscopic images in Figure 1 and 2 are that of a normal guttural pouch in a horse. There are 2 guttural pouches in the horse and their role is not clearly defined. However, there are several very important structures which course through the guttural pouches. These include large veins and arteries plus critical cranial nerves (Figure 2) . Each guttural pouch is divided into a medial and lateral compartment by a unique bone named the stylohyoid bone. This bone articulates with the base of the skull, just below the ear drum and is part of the support structure for the tongue and larynx! As such, when the horse moves its tongue the articulation between the stylohyoid bone and the base of the skull moves as well. The large blood vessels located within the guttural pouch are important for bringing oxygenated blood to the brain and draining deoxygenated blood from the brain. Equally important are the cranial nerves that course through the guttural pouches. These nerves are essential for a proper swallowing reflex, sensation to the face, and balance.

Figure 1

Figure 2

The endoscopic images in Figures 3-5 are from a gelding that presented for a history of purulent nasal discharge that responded to antibiotic treatment. The endoscopic exam was requested as a follow-up to make sure there was nothing lurking in the horse's upper airway. When the right guttural pouch was entered, a large white plaque was noted covering the entire stylohyoid bone. There was minimal discharge within the pouch and there appeared to be mold covering the surface of the plaque!!

Figure 3

Figure 4

In Figures 4 and 5, the proximity of the fungal plaque with the large blood vessels and important nerves can be seen. Normally, fungi seek out vascular tissue and slowly erode the walls of vessels which can result in low grade bleeding and if it is a large artery, sudden death!! Commonly, horses with fungal infection or mycosis of the guttural pouch present with a history of a bloody nose (epistaxis), however this horse did not. When the plaque was disturbed with the scope, the underlying tissue was exposed and the inflammation was evident.  A bacterial and fungal culture was performed on the fluid recovered during the guttural pouch lavage and a fungi was recovered yet the identity is still being worked out. This condition is difficult to treat and is currently being managed with systemic antifungals and guttural pouch lavage. Stay tuned!!!!

Figure 5

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. 

Suspensory Break Down!

The suspensory ligament has been significantly stretched and strained, resulting in the "dropped fetlock" conformation seen below. The suspensory ligament (blue structure in drawing below) originates just below the hock in the hind limbs and the carpus in the forelimbs. The ligament splits into a medial (inside) and lateral (outside) suspensory branch. The split occurs approximately half way down the metatarsus. Each suspensory branch inserts on a sesamoid bone at the level of the fetlock and play a role in "suspending" the fetlock. For the fetlock to drop, the suspensory branch and body have been strained and maybe even ruptured. For definitive diagnosis, an ultrasound exam is performed that will evaluate the entire suspensory ligament. If the process is slow (months to years), it may result in reduced performance and low grade lameness. However, if sudden, significant lameness is associated with the limb or limbs affected. Unfortunately, this is a progressive condition that will ultimately result in retirement of the horse and may be life-threatening. Management of this condition includes reduced exercise, daily ice therapy, corrective shoeing, and daily pain management. This condition carries a poor prognosis for return to work and a guarded prognosis for over-all soundness.

The blue structure depicts the suspensory ligament in the forelimb. Note the upper region is one structure (body) which then splits into two branches.

These are known as "fish tail" shoes and are quite effective in reducing the strain on the suspensory ligaments. For obvious reasons, this type of shoe, with significant heel extension, can only be used in the hind limbs.