IN THIS NEWSLETTER:
Infection with the bacterial organisms Actinomyces bovis and Nocardia asteroides is seen not infrequently in our practice. Most commonly we see these infections in field trial and hunting dogs. Summer conditioning of these dogs, especially those taken to Canada or the Dakota’s, seems to be associated with increased prevalence of infections. Both bacteria are found throughout nature, commonly in the soil (Nocardia), and in the oral cavity and bowel (Actino). Clinically, symptoms of infection with either organism cannot be differentiated and they will be discussed together. Route of infection appears to be either through penetration of skin, inhalation, or penetration of mucosal barriers after ingestion. Frequently, it appears the organism and infection is associated with contamination of a body cavity by a foreign body such as a grass awn (speargrass, foxtail). In the hunting dogs, it appears inhalation or ingestion of the grass awn are the primary modes of entrance, with subsequent migration of the awn to a body cavity. Several clinical syndromes of infection have been described; our focus will be on the two most commonly seen in our practice.
The thoracic form of infection occurs when a grass awn migrates via the lung tissue into the thoracic cavity. Dogs may present with a dry, non-productive cough, or simply be presented for exercise intolerance. Symptoms may be gradual in onset, especially in highly trained, athletic dogs. Chest radiographs may demonstrate fluid within the chest cavity (pyothorax) with a mass or masses within the lung lobe(s). Recently, I have seen two cases with a diffuse bronchointerstitial pneumonia rather than a mass lesion and pyothorax. Thoracocentesis in cases with pyothorax demonstrates a consistently foul-smelling, “tomato soup-like” fluid which is usually a greyish-yellow to reddish-brown in color. Granules may be noted in the fluid. When submitting cultures, be sure to notify the lab you are looking specifically for Actino/Nocardia infection as special culture media and a prolonged culture duration is required. Thoracotomy is usually indicated, with aggressive surgical debridement plus/minus lobectomy. Mortality rates of approximately 50% may be expected. Conservative treatment is not effective.
The cutaneous form is the other frequent manifestation of disease that we see. It may be characterized by a draining tract on the extremities, but more often we see a large abscess-type lesion on the thoracic wall, or just caudal to the last rib on the abdominal wall. Draining the abscess rarely results in a cure. Surgical exploration with aggressive debridement is needed. Identification of a foreign body markedly improves the odds of success, with success rates of 90% expected if a foreign body is found.
Recurrent infection, or persistent low-grade infection may be noted. Aggressive, long-term antimicrobial therapy is needed. Since the organisms are difficult to culture, treatment many times must be done in the absence of a definitive culture and sensitivity finding. Combination therapy with penicillin/amoxicillin plus sulfa-trimethroprim for one month is suggested. Alternatively, 11 mg/kg clindamycin BID, used for 30 days, is appropriate based upon recent communication with a veterinary microbiologist. Cost or side effects may dictate antibiotic choice.
Awareness, early detection, and aggressive treatment of these infections
improves success rates dramatically. Hopefully, this will serve to
heighten the suspicion and recognition of Actinomyces and Nocardia infection.
Far and away the most common procedure performed in our practice is repair of cranial cruciate ligament injury in the dog. Although numerous techniques are available, there are basically two categories within which these procedures fall: intra-articular reconstruction and extra-articular stabilization.
Of the intra-articular techniques described, the procedure I prefer is the modification of Arnoczky’s Over-the-Top technique as described by Dr. Don Hulse. While surgical technique is important for optimal results, the intent of this brief discussion is to focus on what happens within the knee joint after placement of the graft.
The fascia lata autograft used in this surgical procedure is left attached distally to the tibia. This graft is then passed through the joint and anchored to the lateral femoral condyle. A variety of methods have been described for anchoring the free end of the graft to the bone. Bone screws, stainless steel orthopedic wire, Kirschner wires, and suture material have all been utilized. The important point to remember is that during the initial 2 to 12 weeks postoperatively, the material anchoring the graft is important to stabilization of the knee. After that period of time, fibrosis of the graft to the femoral condyle is adequate to anchor it to the femur. Absorbable suture should not be used.
Establishing blood supply to the graft is a slow process which requires the migration of vessels into the graft tissue from vasculature arising within the infrapatellar fat pad and surrounding synovial tissues. Revascularization of the graft is extremely important to the healing process, and the infrapatellar fat pad must not be resected. Complete revascularization does not occur until approximately 20 weeks postoperatively. In this interim period, the fascia lata initially acts as a free tissue autograft which may first weaken, and then slowly strengthens. Studies have shown that the amount of anterior drawer movement initially increases, especially during the first 4 weeks postoperatively. There is then a slow decrease of drawer motion back toward normal values at 6 months under optimum conditions.
Protection of the graft and controlled mobilization of the knee are important if we are to have ideal results. Achieving this is problematic due to our inability to communicate directly with our patients and the fact that we must rely heavily on owner compliance. From the studies, it is clear that the initial 4 weeks are extremely critical, and out to 12 weeks we are still relying upon the mechanical properties of our implant material (suture, stainless steel, etc.) to secure the graft tissue to the bone. It behooves us to educate our clients about the important role they play in achieving surgical success. The client must also be aware of the amount of time it takes for the knee to heal properly. Clear communication and strict adherence to our postoperative instructions are imperative if we are to achieve consistently good results with intra-articular cruciate repair.
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BRACHYCEPHALIC UPPER AIRWAY SYNDROME
Brachycephalic upper airway syndrome is a “catch-all” phrase used to describe a multitude of problems noted in brachycephalic breeds of dogs which manifest as either respiratory distress, or a disproportionate amount of upper airway noise. Most commonly, we see this condition in the various strains of Bulldogs, as well as Shih Tzu’s, Lhaso’s and other dogs with similar facial characteristics. The problem, which is a man-made condition, results from generations of breeding dogs who have too much soft tissue for their limited skeletal (skull) capacity.
Many dogs are referred here to “have the soft palate clipped”, a term breeders often use which does a disservice to the degree and sophistication of skill necessary for us to alleviate these dog’s problems. A complete evaluation of the nares, the soft palate, and the larynx must be done in all dogs in which surgery is contemplated if we are going to have consistent success. Additionally, certain breeds are noted for a congenitally small trachea, and thoracic radiographs should be done in these dogs to exclude that as a contributing factor to the respiratory distress. A lateral view of the chest should show that the tracheal diameter at the level where it crosses the 3rd rib is at least 3 times the size of the rib. This is a crude but useful guideline for the practitioner to rely upon, and gives us good information upon which to base a surgical recommendation and prognosis.
Evaluation of these dogs should start with a visual examination of the nares. Stenotic nares are common, and require correction in order to minimize the open-mouth breathing commonly noted in these dogs. Surgical techniques for all conditions vary in this syndrome and the reader is referred to various surgical texts. Many techniques are based upon personal preference.
Next, under sedation or light anesthetic, the oral cavity should be examined. The tonsils should be visualized and noted if they protrude excessively from the tonsillar crypts. Tonsillectomy may be an adjunct procedure done in some dogs.
The soft palate is visualized and noted to be either normal, elongated, or short. The normal soft palate should slightly overlap the tip of the epiglottis so that as the dog swallows, aspiration of food or water does not occur. A soft palate extending well beyond the tip of the epiglottis is elongated and should be shortened surgically. Guidelines for appropriate length of the resection are published, and it is wise to err on leaving the soft palate too long, rather than too short. Additional tissue can be removed at a later date if needed; it cannot be easily added!
The glottis is evaluated for two abnormalities: everted laryngeal saccules, and breakdown and collapse of the laryngeal cartilage. A folding of the arytenoid cartilage into the lumen of the glottis may be seen late in the syndrome and seems to portend a poorer functional surgical outcome, in my experience. This is a late finding and can be, many times, prevented by early recognition and surgical correction of many of the above abnormalities when the dog is first diagnosed.
A short comment on pre-surgical preparation of the patient should be
made. Once handling of the soft tissues of the airway commences,
swelling is noted shortly. I premedicate all dogs with corticosteroids
and broad-spectrum antibiotics. Atropine or glycopyrrolate is used
in most dogs and the endotracheal tube is left in until the dog is completely
awake. Overnight observation and 24 hour care should be available,
and the surgeon should be capable of doing an emergency tracheotomy if
required. Please call our office if you have any questions about
this condition in a patient.