ANZCVS 2009/2010

Question 1

a) Write brief notes on the phases of wound healing in a skin incision

Answer 1

Wound healing can be divided in 3 major phases – Inflammatory, proliferation and remodeling.

The INFLAMMATORY PHASE is subdivided into hemostasis, cell migration and debridement sub-phases. In the hemostatic sub-phase, platelet clusters are formed, clotting factors are activated and blood vessels contract as part of sympathetic response to control hemorrhage. This is followed by the cell migration phase, with migration of Inflammatory cells, initially neutrophils and later monocytes. These cells release chemotactic factors that promote vasodilation, conversion of cell membrane phospholipids by cyclooxygenase into prostaglandins and thromboxane as well as activation of complement system. Capillaries rapidly sprout to improve blood supply to the area. During the debridement phase capillaries continue to sprout, and microorganisms and devitalized tissue are removed primarily by macrophages (monocytes that left blood vessels), which also secrete growth factors and attract mesenchymal cells. Neutrophils also phagocytize bacteria but are less important than monocytes/macrophages. Lymphocytes are also present and contribute to the immunologic response to foreign debris.

The PROLIFERATION PHASE consists of fibroblast, capillary, and epithelial proliferation sub-phases.
During the fibroblast sub-phase (day 3) mesenchymal cells differentiate into fibroblasts, which lay fibrin strands and collagen to form a framework upon which cellular migration can occur. Wound quickly gains strength. Collagen is later reorganized according to wound stress. During the capillary sub-phase, capillaries migrate following an oxygen deficit gradient (low oxygen at the center of the wound), supporting further fibroblast proliferation (O2 dependent). The combined capillary/fibroblast proliferation result in granulation tissue, which is friable and resistant to infection. The epithelial cell migration sub-phase begins within hours of injury. Basal epithelial cells flatten and migrate across the open wound, as well as secrete growth factors Alpha and Beta to enhance wound closure. Cells continue to migrate until contact inhibition is achieved (48 hours for properly closed surgical wound.). This requires a proper granulation bed, and epithelial migration is delayed by desiccated wounds.

During the REMODELING PHASE, collagen bundles and fibroblasts are reorganized according to the lines of tension, and fibers in a nonfunctional orientation are replaced by functional fibers. This allows the wound to continue to gain strength over long periods of time (> 2 years).

Question 2

b) List 7 host factors that can affect wound healing and make brief noted on how they affect healing

Answer 2

1) Endocrine disease – conditions like hyperadrenocorticism lead to excessive corticosteroid production, which will inhibit angiogenesis, fibroblast proliferation and rate of epithelialization. Hypothyroidism and DM may have a similar effect
2) Immune Status – immune-suppressive diseases and certain drugs may affect the inflammatory and proliferative phases of healing by impairing the host’s ability to control opportunistic infection
3) Malnutrition / hypoalbuminemia – Hypoproteinemia, particularly hypoalbuminemia, secondary to poor nutrition or protein-loosing enteropathy/nephropathy my lead to deficient collagen production and delayed increase in tissue tensile strength.
4) Anemia – Affects oxygen delivery to tissues
5) Skin colonization with antibiotic-resistant bacteria – More recent issue that may lead to wound infection by collagenase-producing bacteria and poor response to antibiotic therapy.
6) Metabolic disease – renal disease, for example, may lead to uremia that slows down granulation tissue formation and leads to poor quality collagen.
7) Hypothermia – more commonly observed intra-op/post-op, leading to impaired inflammatory response (first phase) and increased propensity to infection.

Question 3

c) List 8 wound characteristics that can affect wound healing, and make brief notes on how they affect healing.

Answer 3

1) Mechanism of onset – Wounds deriving from pathology, such as envenomation or infarcts, or wounds deriving from trauma (i.e. burns) heal more slowly than surgical wounds
2) Time of onset – Chronic wounds are more often associated with tissue changes and take more time to heal.
3) Location – wounds located on bony prominences and areas of decreased vascularity.
4) Wound dimensions – Larger wounds naturally take more time to heal, but wound shape also plays a part in the process. Linear wounds heal fastest, followed by rectangular/square, followed by circular (slowest).
5) Temperature – The colder the wound, the slowest it will heal. This is likely a result of decreased wound oxygenation and nutrition caused by vasoconstriction.
6) Wound hydration – dry wounds develop a crust that inhibit epithelial migration, delaying resolution of the inflammatory phase. Excessive moisture can cause wound edge maceration.
7) Necrotic tissue – devitalized tissue is prone to infection and must be removed by macrophages during the debridement phase of inflammation
8) Infection – Infection delays healing by prolonging inflammation, encouraging dehiscence and increasing scarring.

Question 4

a) Write short notes on the clinical signs and pathogenesis of megacolon in cats

Answer 4

Feline megacolon is most commonly idiopathic but may also be a result of obstructive disease (neoplasia, old pelvic fractures), neurologic disease, endocrine disease, congenital or behavioral. The idiopathic form is believed to be secondary to a generalized dysfunction of the colonic smooth musculature. Clinical signs include tenesmus, diarrhea (liquid passing around fecal concretions), nausea, vomiting (toxin absorption, vagal stimulation) inappetence and weight loss. The pathogenesis includes progressively larger stool accumulation which becomes dehydrated and solidified, frequently reaching volumes so large as to render passage through the pelvic canal impossible.

Question 5

b) Write short notes on the clinical signs and pathogenesis of reverse shunting in a dog with Patent Ductus Arteriosus

Answer 5

The ductus arteriosus is a fetal vessel communicating the descending aorta and the main pulmonary artery, allowing shunting of fetal oxygenated placental blood from the pulmonary artery to the systemic circulation and bypassing the non-functioning fetal lung. This structure quickly contacts due to increase oxygen tension and is meant to undergo fibrosis and necrosis within a few weeks after birth. If the ductus remains patent, blood continues to partially bypass the lungs in a left to right pattern (Aorta to pulmonic artery, due to higher pressure gradient) leading to a murmur, increased pulmonary blood flow and gradual left ventricular eccentric hypertrophy that may evolve into ventricular failure and pulmonary edema. Common clinical features include a bounding pulse and loud murmur. Reverse shunting (pulmonic artery to aorta, or right to left) occurs when there is an increase in the pulmonary vasculature. These dogs have diminished pulmonary flow, small left ventricle and marked hypertrophy of the right ventricle (due to increased pulmonary vascular resistance). Clinical features are very different from those of the most common left to right shunt, and include a soft or no murmur, differential cyanosis (cyanosis of caudal mucous membranes with pink cranial membranes) and secondary polycythemia/hyperviscosity due to renal hypoxemia.

Question 6

c) Explain, with the aid of a diagram if you like, the term “pseudohypereflexia” and how it might occur in a dog with L4-S3 localizing spinal lesion

Answer 6

The term “pseudohypereflexia”, as it applies to a L4-S1 spinal lesion, refers to the exaggerated patellar reflex despite the presence of a lower motor neuron injury. This happens when the roots of the sciatic nerve are involved, particularly L7, while those of the femoral nerve (L4-6) remain intact. Under normal conditions the sciatic nerve provides motor control to the stifle flexor muscles that counteract the knee jerk reflex elicited by a sudden stimulus directed against the quadriceps muscle spindles (femoral nerve). In the absence or decrease of these flexors that patellar reflex becomes exaggerated, mimicking a UMN segmental reflex patter. These patients typically have absent gastrocnemius reflex and withdrawal reflex limited to hip and stifle.

Question 7

a) Describe the anatomy and functions of the omentum. Give examples of three different surgical conditions in which you would consider utilizing the omentum to make use of the functions you have described.

Answer 7

The omentum is anatomically divided into greater and lesser omentum. The Greater omentum is larger and folds between the stomach and dorsal body wall. This creates two walls known and paries superficialis, attached to the greater curvature of the stomach and paries profundus, attached to the dorsal body wall cranial to the cranial mesenteric artery. The wall of the greater omentum is covered by a double peritoneal sheet with streaks of fat around arteries – one of the major fat stores in overweight animals. The Lesser omentum is smaller and originates on the lesser curvature. It contains the hepatogastric and duodenogastric ligaments and constitutes the ventral border of the epiploic foramen which contains the hepatic artery, portal vein and bile duct. The omental blood supply derives from the right and left gastroepiploic arteries. The functions of the greater omentum include adipose tissue storage, immune-regulation, hemostasis, lymphatic drainage, tissue regeneration and enhancement of blood supply (neovascularization).These functions can be relied upon by creating a temporary attachment or inclusion of the omentum (omentalization) around enterotomy sites, intestinal resection/anastomosis sites, chylothorax (trans-diaphragmatic technique), surgically-treated pancreatic or prostatic abscesses, renal cysts, partial colectomy, transabdominal omental flaps, among others.

Question 8

List the physical forces that must be overcome when stabilizing bone fractures by any means to allow bone to heal

Answer 8

Bending, torsion, axial loading, shearing, distraction

Question 9

b) Describe the process of bone healing that is expected to take place following the application of a DCP plate to a closed, mid-diaphyseal, transverse femoral fracture.

Answer 9

A compressed fracture of this type is expected to heal by direct fracture healing (contact healing). This process occurs when the fracture is anatomically reconstructed, stable (minimal interfragmentary strain) and compressed (gap less than 0.01mm)) enough to allow the formation of cutting cones at the ends of the osteons on either side of the fracture. The tips of these osteons are composed of osteoclasts that generate longitudinal cavities at a rate of 50 to 100 um/day. These cavities are later filled with bone produced by osteoblasts residing at the rear of the cones. This results in generation of a bony union and restoration of Harversian systems in the axial direction. The re-established Harversian systems allow penetration of blood vessels carrying osteoblastic precursors. The bridging osteons are later remodeled into lamellar bone, resulting in healing without a periosteal callus.

Question 10

c) Describe the neuromuscular control of urine storage and voiding

Answer 10

Urine storage and voiding are controlled by a combination of parasympathetic, sympathetic, and somatic control. The parasympathetic innervation derives from pelvic nerves, the sympathetic innervation for hypogastric nerves and somatic from sacral and pudendal nerves.

Urine storage: Facilitated by the urethral sphincter and hypogastric nerve. Stretching (pressure) is detected by muscle spindle of striated muscle and transmitted to the pudendal nerve and sacral spinal cord segments (L7-S3, Onuf’s nucleus, ventral horn). Once stretch threshold is reached a direct motor response via the pudendal nerve activate the external urethral sphincter. The external component of the urethral sphincter is also under cortical influence, allowing voluntary contraction or inhibition, as well as under pelvic nerve control which inhibits pudendal nerve firing during detrusor muscle contraction. The hypogastric nerve (L1-L4) provides alpha and beta adrenergic synapses. The alpha-adrenergic component synapses to the trigone, neck and proximal urethra causing contraction. The beta-adrenergic component synapses with the detrusor muscle, causing muscle relaxation.

Voiding: Sensory input to bladder filling is transmitted through pelvic nerves from the detrusor muscle (smooth) to sacral spinal cord segments which communicate with ascending tracts to the pontine reticular formation. The pontine reticular formation is responsible for the micturition reflex through activation of parasympathetic influence (pelvic nerve), reduction of sympathetic input (hypogastroic) and inhibition of sphincter muscle contraction (pudendal). The cerebellum also participates via inhibition of detrusor activation. Pelvic nerves inhibit hypogastric neurons during voiding

Question 11

a) List and briefly describe the different mechanisms of antibiotic action and give an example of an antibiotic of each mechanism described.

Answer 11

Six primary mechanisms of action:

1) disruption/inhibition of synthesis of bacterial cell wall. Examples: Beta-Lactam antibiotics, including penicillins, cephalosporins, carbapenens, monobactans, vancomycin, Polymyxin B and nystatin.
2) inhibition of cellular protein synthesis. Aminoglycosides, tetracyclines, chloramphenicol, clindamycin
3) Inhibition of DNA synthesis. Fluoroquinolones like enrofloxacin and marbofloxacin, as well as metronidazole
4) Inhibition of RNA synthesis. Rifampin
5) Inhibition of Mycolic acid synthesis. Isoniazid
6) Inhibition of Folic acid synthesis. Sulfas and trimethoprins

Question 12

b) Hypotension is a common perianesthetic complication in small animal patients. The pathogenesis of hypotension is multifactorial. List two factors that may contribute to hypotension in an anesthetized patient. Describe methods of monitoring blood pressure during surgery in small animals and give an indication of the normal blood pressure range. List three actions you can take to correct hypotension during surgery.

Answer 12

Two factors: Hypothermia and induction/maintenance drugs; Monitoring accomplished via direct or indirect measurements techniques. The former include arterial and/or venous catheters connected to an automated or analog (water column)gauge. The latter include Doppler/sphygmomanometer or oscilometric systems. Normal peripheral systolic blood pressure ranges from 100 to 120 mmHg; Mean peripheral systolic pressure 80-100 mmHg

Question 13

)Briefly describe the anatomy of the parathyroid glands in the dog. Write short notes on the clinical signs associated with a functional parathyroid tumor in the dog.

Answer 13

The parathyroid glands are paired bilateral glands measuring 2 to 3 mm in a mid-size dog. Each gland is divided into external and internal parathyroid glands. The former is usually located on the cranio-dorsal aspect of the thyroid gland, and the latter near the caudal pole. The parathyroid glands may vary in position, being occasionally found in contact, not in contact or even within the parenchyma of the thyroid gland (under the thyroid fascia). Variations in location and number of parathyroid glands are frequently reported. They derive their blood supply from the cranial thyroid artery, which is a branch of the common carotid artery.
Clinical signs associated with functional parathyroid disfunction stem from hypercalcemia and hyperphosphatemia, and may include polyuria, polydipsia, dystrophic calcification, cystic calculi, constipation, and weakness.

Question 14

Using diagrams, describe the Salter-Harris fracture classification

Answer 14

Question 15

The initial intent of the Salter-Harris system was to provide prognostic information. However, this has not proven to be a valid concept. Explain what other important prognostic factors must be considered when dealing with such fractures.

Answer 15

Prognostic factors that may influence the development of complications, particularly angular limb deformities, include degree of displacement, timing of surgical stabilization (operative delay is detrimental), age (degree of physeal closure vs remaining growth potential), ability to achieve anatomical reconstruction (most important factor) and stability of the repair.

Question 16

c) Name the microanatomic zones of the physis

Answer 16

From epiphyses to metaphysis (RPHO) – Reserve zone, Zone of Proliferation, Zone of Hypertrophy, Zone of provisional ossification

Question 17

d) Indicate in which zone the physis fractures usually occur

Answer 17

Zone of hypertrophy (sub zone of calcification)

Question 18

e) Define the term “distraction osteosynthesis” and make notes on what occurs at the cellular level during distraction osteosynthesis.

Answer 18

Distraction osteosynthesis is defined as the creation of an osteotomy followed by the application of a device that allows gradual and incremental separation between bone segments. This leads to continuous bone formation.
The “latency period” starts immediately after the osteotomy and extends to the beginning of the distraction. It is characterized by proliferation of fibroblasts and induction of periosteal reactivity. This allows organization of the hematoma and fibrous tissue matrix which will serve as mold to osteoblast proliferation. This will lead to the production of osteoid in the first 24 hours. There is also periosteal and endosteal revascularization. During the “distraction period” fibroblasts deposit collagen into organized fibrils, leading to the formation of the radiolucent fibrous interzone (FIZ). The FIZ cells eventually differentiate into osteoblasts and begin to deposit bone matrix to form micro columns. Mineralization proceeds along collagen fibers, parallel to distraction zones. The last period, named “consolidation period” is characterized by mineralization of the FIZ which becomes sclerotic. The columns of regenerated tissue become progressively more homogeneous as primary bone tissue is replaced by Harversian bone. This takes approximately 8-12 weeks to form new cortex and medullary cavity.

Question 19

f) List two different clinical examples of when you would consider using distraction osteosynthesis.

Answer 19

Angular limb deformity to correct limb length disparity. Bone stock lengthening following the removal of malignancies.

Question 20

a) List the tendons that comprise the Achilles mechanism in the dog

Answer 20

Gastrocnemius (major component), superficial digital flexor + common tendon (semitendinosis, gracilis and biceps femoris)

Question 21

b) Describe the clinical signs associated with injuries to this tendon group

Answer 21

Acute or chronic onset of tarsal hyperflexion, ranging from partial to a complete plantigrade stance. The tendon is perceived as flaccid when the tarsus is flexed with the stifle extended. If the tendon of the superficial digital flexor is not involved, the Tarsus will hyperflex and the digits will flex. The tendon may also be palpably swollen, particularly in acute cases.

Question 22

c) Describe the ideal properties, and give one example, of the suture material you would use to perform an end-to-end anastomosis of an Achilles tendon severed 2 cm proximal to the tuber calcis in a 30kg dog

Answer 22

Nonabsorbable, non-reactive, mono or multifilament material of high tensile strength and excellent knot security properties. Example: Arthrex FiberWire (ultra-High molecular weight polyethylene with braided polyester jacket). 0, 1 or 2 PDS or Nylon are also acceptable but less strong options.

Question 23

d) Name and give a brief description or a diagram for recommended suture patterns or techniques used in primary tendon repair. Explain why you would choose one of them.

Answer 23

Two most common patterns are utilized –
Locking-Loop : Most versatile suture pattern in small-animals, particularly for flat tendons.

The transverse component must pass superficial to the longitudinal parts to encircle a bundle of fibers between the loop.

Three-loop pulley: best for round tendons. This technique roughly follows a “near-far-far-near” pattern

Question 24

e) Write short notes concerning the postoperative management of the case described in part c. Your answer should reflect your knowledge of tendon healing and how to maximize it.

Answer 24

Most complications associated with common calcaneal tendon repairs stem from the various immobilization methods utilized to allow prolonged contact between the severed tendon ends. These may include a calcaneotibial screw, external fixator or external coaptation. A calcaneotibial screw is easy to apply and very effective. Regardless of the method used, the immobilization must be maintained through the proliferation and into the remodeling phase, generally 6 - 8 weeks for tendons. Ideally strict immobilization should be maintained for the first 3 weeks, followed by controlled load or strain to lead to more rapid repair. This is typically not actively pursued in the case of the common calcaneal tendon because the gastrocnemius pull is never entirely eliminated.

Question 25

a) List of potential sources of infection associated with septic arthritis

Answer 25

hematogenous sources

• penetrating wounds
• surgical
• Local spread from adjacent tissues

Question 26

b) Briefly describe the cytological features of septic joint fluid

Answer 26

Polymorphonuclear leukocytosis (primarily neutrophils) with degenerative and toxic changes such as pyknotic nuclei, degranulation and cell rupture. Intracellular bacteria may be present and is pathognomonic for septic arthritis, but only observe in the minority of cases. High protein concentration

Question 27

List the most common bacterial isolates in Septic joint fluid from a dog

Answer 27

Staphylococcus intermedius, Staphylococcus aureus and beta-hemolytic Streptococcus

Question 28

d) Explain how bacteria can be isolated, for the purpose of culture and sensitivity, from the joint fluid of a dog with septic arthritis

Answer 28

Joint fluid must be aseptically collected and added to blood culture medium. Synovial biopsy can also be considered for higher likelihood of obtaining a positive culture.

Question 29

e) Write brief notes on the medical and surgical treatment of septic arthritis

Answer 29

The management may include a combination of joint fluid aspiration, joint irrigation, arthroscopic synovectomy as well and systemic and local antibiotic delivery. Systemic antibiotics may initially be delivered intravenously to rapidly establish tissue concentration. In the absence of a positive culture, broad-spectrum antibiotics should be selected. Examples may include Beta-lactam ring antibiotics like amoxi/clav, cephalexin with or without metronidazole. Therapy is continued for a minimum of 28 days or until synovial fluid composition returns to near-normal (repeat joint-fluid total and differential cell counts every 7 to 14 days). Absorbable and non-absorbable antibiotic delivery systems (collagen, PMMA, etc… ) are also available and frequently used for antibiotic-resistant infections.

Question 30

f) Explain the short and long-term prognosis you would give a 16 week old boxer diagnosed with elbow join sepsis

Answer 30

Septic arthritis is rarely encountered in young dogs, and most likely developed as a consequence of preexisting joint disease in this dog (likely elbow dysplasia). The short-term prognosis could be fair if the clinical signs (arthralgia, fever, synovial fluid cell population) promptly respond to antibiotic therapy. The long term prognosis is likely to be less favorable depending on the degree of synovitis and fibrin production within the joint. These factors will determine how much cartilage damage the patient will sustain and how functional the joint will be in the future.

Question 31

a) Describe the typical signalment of perineal herniation in a dog

Answer 31

Perineal hernias typically present as soft, non-painful, non-ulcerated swelling in the perineal region. They can be unilateral or bilateral. Clinical sign vary from none (except for visible swelling of the region) to straining during defecation (most commonly) as a result of fecal accumulation in a deviated or dilated rectum. More acute clinical signs may also result from obstruction, incarceration or strangulation of herniated organs. Patients with urinary bladder retroflexion may present unable to urinate, azotemic and dehydrated with a firm perineal swelling.

Question 32

b) Explain the possible causes of perineal herniation in the dog

Answer 32

There are many proposed causes of perineal herniation in the dog. These include:

1) rectal abnormalities (rectal deviation, rectal diverticulum- likely a result of herniation but contributes to straining and further weakening of the pelvic diaphragm)
2) The effect of androgens (predominantly observed in intact males; neutering significantly decreases the chance of recurrence)
3) Gender-related anatomic differences (the female pelvic diaphragm is larger, broader and stronger than that of males)
4) Relaxin hormonal effect (affects collagen metabolism, causing relaxation and stretching of inelastic tissues. Affected dogs have higher expression of relaxin receptors within the pelvic canal)
5) Prostatic disease (Observed in 25 to 50% of dogs with perineal hernias. Possible due to prostatomegaly leading to increased abdominal pressure during urination, caudal displacement of the prostate or periprostatic cysts.
6) Testicular disease (observed in 69% of dogs with perineal hernias – cause-effect no established)
7) Neurogenic atrophy (neurogenic atrophy of the coccygeus and levator ani muscles due to nerve damage to the muscular branches of the pudendal and pelvic nerves. Possibly resulting from a degenerative neurogenic myopathy. Tenezmus from prostatic enlargement has been suggested as the cause of traction applied to the sacral plexus nerves.

Question 33

c) Explain the surgical technique options for the management of a 10 year old intact male with bilateral perineal herniation

Answer 33

Various surgical techniques have been described since the original Farquharson technique from 1940. These include transposition of the internal obturator, superficial gluteal of semitendinosus muscles, as well as various prosthesis and biomaterials. The goal is to perform a slightly curvilinear incision around the anus (convex side faces the anus) of sufficient size to remove serous fluid and retroperitoneal fat, reduce the hernia contents into the abdomen, avoid damage to the internal pudendal and caudal rectal vessels as well as the caudal rectal nerve, rebuild the pelvic diaphragm using one of the techniques mentioned above, lavage the area thoroughly and close the wound in standard fashion. Sutures are typically pre-placed prior to tying. Castration is highly recommended.

1) The traditional technique involves placement of sutures (2-0 or 0 PDS or polypropylene) between the external anal sphincter and the levator ani and coccygeous muscles. The sacrotuberal ligament (dogs) can be used of these muscles are severely atrophied, but care must be taken to place these sutures through and not around the ligament to avoid caudal gluteal vessel and sciatic nerve entrapment.
2) The internal obturator muscle transposition involves incising this muscle along its caudolateral border, elevation from the ischium with periosteal elevator taking care not to extend the elevation into the obturator foramen. The insertion tendon is identified near the trochanteric fossa, and is transected medial to the point where it crosses over the border of the ischium to avoid damage to the sciatic nerve. The muscle is transposed and sutured to the coccigeous and external anal sphincter.
3) During the Superficial Gluteal Muscle Transposition the incision is extended ventrally until the muscle can be isolated near its insertion on the third trochanter of the femur. A tenotomy is performed and the muscle is retracted to cover the ischiorectal fossa and is sutured to the external anal sphincter. Part of the tensor fascia Lata can also be included to broaden the flap. The belly of the muscle is sutured to tissues above and below the fossa. Techniques that combine internal obturator and superficial gluteal muscle transposition have also been described.
4) Semitendinosus muscle transposition is useful as a “salvage” procedure when other techniques have failed. It can be transposed 180 degrees to fill ipsilateral hernias or 90 degrees to fill contralateral hernias with a ventral defect.
5) Prosthetic implants like Polypropilene or Polypropilene-polyglecaprone mesh can be used alone or in combination with the techniques above. Mesh orientation is important as it will accommodate much higher load when its longitudinal cords are oriented parallel to the tension axis. The mesh is sutured to the same muscles or it can be anchored directly to the ischium ventrally.
6) Biomaterials like porcine small intestinal submucosa (BioSIS), porcine dermal collagen and autologous fascia (typically fascia lata, but also lumbar fascia) can also be used.

Organopexy (colopexy, cystopexy and/or deferensopexy may also be used to reposition and stabilize viscera in their anatomic locations. This can be considered as a separate procedure, typically 1 week prior to herniorrhaphy, to decrease swelling, edema and improve visibility of normal anatomy during herniorrhaphy.

Question 34

d) List five possible complications of perineal herniorrhaphy, For each complication, explain how you could minimize the risk

Answer 34

1) Sciatic nerve/Caudal gluteal vessel entrapment - place sutures through and not around the ligament to avoid caudal gluteal vessel and sciatic nerve entrapment.
2) Surgery site infection – minimized but strict adherence to aseptic technique, minimal dissection of tissues, closing dead space, controlling fecal contamination (no enemas; manually empty rectum prior to procedure; apply purse string suture)
3) Fecal incontinence- Temporary incontinence occurs in 30% of cases, particularly in bilateral surgeries. This can be minimized by careful identification and preservation of the caudal rectal and pudendal nerves (challenging at times)
4) Urinary Tract Complication – Typically bladder atony as a result of retroflexion. Anuria may be caused by inadvertent suturing of the urethra, and can be minimized by careful suture placement
5) Tenezmus – Typically a result of excessive inflammation and pain or severe rectal dilation, but also occasionally due to excessive tension caused by bilateral repairs or sutures penetrating the rectal wall. Adequate tissue release and/or combination of techniques and careful suturing can decrease the chance of such complication.

Question 35

a) Explain the animal and husbandry factors that may be associated with an increased risk have a dog developing gastric dilatation and volvulus (GDV)

Answer 35

Animal risk factors include being of a pure breed, giant breed, increased thoracic depth-to-width ration, increased hepatogastric ligament length and having a history of GDV in first-degree relative. Husbandry factors include feeding fewer meals per day, eating rapidly, aggressive, or fearful temperament, decreased food particle size, exercise or stress after a meal.

Question 36

b) Explain how you would determine intraoperatively if gastric resection is required when performing surgery on a dog that has experienced GDV. Explain how the need to perform gastric resection might affect the prognosis for this patient.

Answer 36

The evaluation of the gastric wall is typically based on visual and tactile assessment. Signs of devitalization include gray/green color, thinning of the gastric wall, lack of peristalsis and lack of bleeding upon incision. The presence of gastric necrosis requiring partial gastrectomy has been associated with a poorer prognosis. It also prolongs the surgery, and surgical time is another factor associated with survival

Question 37

c) List the ideal properties of a suture you would choose for gastric resection surgery. Describe the suture type and the suture pattern that you would choose.

Answer 37

The ideal suture for this application is synthetic, absorbable, monofilament non-reactive material such as polydioxanone or poliglecaprone on a taper needle. Size typically 2-0 or 3-0. The mucosa can be closed separately to decrease hemorrhage or left unsutured (heals very quickly) , and the closure will include submucosa, muscularis and serosa. A simple continuous layer is followed by continuous inverting pattern like Cushing or Lambert. Care is taken if the incision extends into the pyloric antrum to avoid excessive invagination and outflow tract obstruction. In this case a Y-U pyloroplasty or Heineke-Mikulicz pyloroplasty can be performed.

Question 38

d) Define the term “gastropexy”. How gastropexy may or may not alter the rate of GDV recurrence in the dog.

Answer 38

Gastropexy is the technique by which a permanent adhesion is created between the stomach and the adjacent body wall. Gastropexy decreases the recurrence rate from nearly 65% to less than 5% and is therefore highly recommended.

Question 39

e) Make brief notes on for methods of gastropexy. Indicate which technique you would recommend and justify your answer.

Answer 39

Several methods to perform a gastropexy have been described over the years. These include the following:

Tube gastropexy – created during exploratory celiotomy via the application of a cranio-ventral transabdominal wall folley catheter. Easy to perform, but must be kept in place for at least 10 days for a permanent adhesion to form. Penetrates the lumen, so risks may include gastric content leakage and peritonitis.

Circumcostal gastropexy – More challenging to perform but creates a very strong adhesion and does not penetrate the lumen. Based on the creation of a one or two-hinge seromuscular flap on the pyloric antrum followed by an incision at the level of the 11th-12th rib at the level of the costochondral junction. Care is taken not to penetrate the diaphragmatic attachments to avoid pneumothorax. A tunnel is created around the rib, the flap is passed under the rib and sutured onto the gastric wall. Risks may include pneumothorax and rib fracture

Muscular flap (incisional) gastropexy – easier than Circumcostal, does not penetrate the mucosa and creates a strong adhesion. Involves a much lower risk of peritonitis, rib fracture and pneumothorax, and creates a reliable adhesion. These are the reasons I would choose this technique for nearly all patients undergoing a celiotory. The technique is applicable for prophylaxis or following treatment of GDV. The main disadvantage is that it does not offer access to the lumen of the stomach for exploration. Based on the creation of a seromuscular incision on the ventral aspect of the pyloric antrum. A similarly-sized incision is created on the peritoneal surface of the ventrolateral right abdominal wall. This incision includes the peritoneum and the transversus abdominis muscle. The edges of the two incisions are sutured using 2-0 absorbable or non-absorbable sutures, simple interrupted or continuous pattern. Care is taken to assure contact between the muscularis layer of the stomach and the transversus abdominis muscle.

Belt-loop Gastropexy – similar to a muscle flap (incisional) gastropexy, but based on the creation of a seromuscular flap which is passed through a muscle tunnel created on the abdominal wall. May created a strong adhesion than the incisional technique, but is more traumatic and technically demanding, and thus rarely performed.

Gastrocolopexy – based on the creation of a seromuscular adhesion between the greater curvature of the stomach and the transverse colon. Rarely performed and associated with a 20% risk of recurrence of gastric volvulus.

Laparoscopy-assisted prophylactic gastropexy - My technique of choice for a healthy patient undergoing a prophylactic gastropexy. One cannula (laparoscope port) is placed 1 cm caudal to the umbilicus, and a second cannula is placed 4 to 5 cm to the right of midline and caudal to the last rib. The pyloric antrum is grasped with Babcock forceps, the canula is removed, the incision enlarged to 4 to 5 cm and the stomach exteriorized. Care is taken not to twist the antrum during retraction of the stomach into the incision. Then gastropexy is accomplished in similar fashion to the muscular flap (incisional) technique, and the ports are closed in standard fashion.

Endoscopically-assisted gastropexy – Based on the passage of a flexible endoscope into the stomach, light insufflation, passage of polypropylene suture transmurally into the stomach and back out to form a mattress suture. The sequence is repeated to apply a second suture 5 cm apart from the first (both on the area of the pyloric antrum). This positions the stomach at the ideal paracostal location, and the gastropexy is performed as described in the laparoscopy-assisted technique.

Laparoscopic sutured gastropexy – based on the use of three portals located at midline and 6 to 7 cm cranial and lateral to the umbilicus (one on either side). The pyloric antrum is grasped and retracted against the right ventral abdominal wall. A coagulation hook probe is used to created four coagulated spots 1 cm apart. A 4cm incision is performed over the coagulated region using laparoscopy guidance. Four large gauge sutures (1-0 PDS) are passed through the abdominal wall and through the seromuscular gastric wall layer, exiting the abdominal wall through the same incision. The serosal surface of the stomach to be incorporated into the suture line is coagulated, three more similar sutures are applied and all sutured are tied to bring the coagulated stomach and peritoneal surfaces in close contact. The skin and portals are closed in standard fashion.

Intracorporal sutured Laparoscopic Gastropexy – Also utilizes a 3-port system like the previous technique. The stomach is suspended and stabilized against the proposed ventral abdominal pexy site using a transabdominal suture. Seromuscular incisions are performed on the abdominal wall and pyloric antrum using laparoscopic scissors or electrocautery. The edges of these incisions are apposed using barbed sutures (most commonly) or automatic suture-assist devices like EndoStitch.

Mini-laparotomy prophylactic gastropexy – Based on a right paracostal approach to the stomach via separation (blunt dissection) between the different abdominal wall layers. An incisional gastropexy is performed as described for the muscular flap (incisional) technique. The muscular, SQ and skin layers are closed in standard fashion. Care is taken to close dead space as best as possible, as seromas are frequently observed with this technique.

Question 40

a) Describe the typical signalment and presenting signs of fibrocartilaginous embolism (FCE). Best diagnostic techniques that can be used to diagnose FCE briefly describe what you might see from each. Describe the clinical features which might help you determine a patient’s prognosis

Answer 40

Signalment: Young to middle-age dogs (1 to 7 years old), large breeds, non-chondrodystrophic (the miniature Schnauzer is the exception here).

Clinical presentation: acute to peracute onset of spinal hyperesthesia and neurologic disfunction that is typically non-progressive after the first 24 hours. The signs of pain initially observed tend to quickly subside. The character of spinal cord disfunction varies according to the location of the lesion (UMN vs LMN). Spinal reflexes are often asymmetrical, implying a unilateral character of spinal cord injury. The thoracolumbar region (T3-L3) is most commonly affected, followed by L4-S3, followed by C6-T2 and finally by C1-C5. Even though spinal hyperesthesia tends to quickly subside in these cases, a focal area of pain corresponding to the site of injury can typically be elicited during spinal palpation.

Diagnostic Techniques: FCE and cerebral infarcts are not typically hemorrhagic in dogs and cats (different from humans), and therefore not evident on radiographs, myelogram or CT.MRI is considered the best diagnostic modality for its ability to highlight soft tissue structures in multiplanar images with little artifact in comparison to CT. Affected spinal cord tissue appears typically hyperintense on T2-weighted and hypointense on T1-weighed MRI images (methemoglobin phase). These areas are minimal to non-contrast enhancing (gadolinium) initially, but contrast enhancement is evident approximately 1 week post-ischemic event likely due to disruption of the blood-brain barrier.

Prognosis: Varies significantly depending on severity of presentation and based on the available literature (conflicting data), but overall it can be said that more severe neurologic impairment is associated with poorer prognosis. Negative prognostic indicators include loss of deep pain, severe lower motor neuron disfunction and owner’s reluctance to pursue physical therapy. Nonambulatory large breed dogs tend to have a guarded to poor prognosis. A ratio of 2 or less vertebral length to lesion length (C6 or L2 depending on affected region) has also been evaluated and determined to be associated with a more favorable prognosis.

Question 41

b) Name the cranial nerve who’s branches innervate the intrinsic muscles of the canine larynx. Indicate which muscle/muscles are responsible for the abduction of the arytenoid cartilages. Briefly describe the surgical approach for the so-called “tieback” surgery treatment of laryngeal paralysis. Your answer state suture type and suture placement within laryngeal cartilages. List possible complications of tieback surgery.

Answer 41

The intrinsic muscles of the larynx are innervated by the paired recurrent laryngeal nerves, branches of the Vagus nerve (X pair of CN’s). The intrinsic laryngeal abductor and cricoarytenoideus muscles control arytenoid position and abduction.
The surgical approach to the arytenoid lateralization or “Tie-back” is based on performing an incision immediately ventral to the external jugular vein, starting at the angle of the mandible and extending caudally along the dorsolateral aspect of the larynx to within 1 to 2 cm caudal to the larynx. Subcutaneous tissue, platysma and parotidoauricularis muscles are incised and retracted. The sternocephalicus muscle and external jugular vein are retracted dorsally, and sternohyoid muscle ventrally to expose the larynx. Palpate the dorsal thyroid cartilage and incise the thyropharyngeal muscle along the dorsal margin of the thyroid cartilage lamina. Place a stay suture through the thyroid cartilage to rotate the larynx laterally. Identify and transect the cricoarytenoideus dorsalis muscle. Disarticulate the cricothyroid articulation with #11 blade or scissors if necessary, followed by disarticulation of the cricoarytenoideus articulation. Place a nonabsorbable monofilament suture (2-0 Prolene) from the caudal 1/3 of the cricoid cartilage near the dorsal midline to the muscular process of the arytenoid cartilage. This mimics the pull of the cricoarytenoideus dorsalis muscle. The sutured should be tied just enough to provide moderate abduction of the arytenoid cartilage, which should be verified by an assistant via oral inspection. Lavage the surgery site and appose the thyropharyngeus muscle with absorbable 3-0 cruciate sutures. Appose SQ and skin routinely.

Possible early complications may include hematomas, swallowing discomfort, temporary epiglottic impairment and incisional issues. Coughing and gagging may be signs of aspiration pneumonia, the most common complication associated with this procedure, affecting approximately 20% of patients. Bilateral procedures increase the incidence of this complication and are thus discouraged. Mineralized cartilages may fracture or avulse the muscular process, causing failure of lateralization and recurrence of clinical signs. Cartilage of young dogs (congenital cases) may be too soft to retain sutures.
Factors associated with a higher incidence of aspiration pneumonia include increasing age, temporary tracheostomy, progressive neurologic disease, postoperative megaesophagus, concurrent neoplasia and the postoperative use of opioids.

Question 42

a) Define axial pattern flap and island axial pattern flap

Answer 42

Axial pattern flaps are skin grafts which include a direct cutaneous artery and vein at the base of the flap. Island axial pattern flaps utilize the same locoregional vasculature but do not maintain a skin connection. They can be used near the harvesting site or the cutaneous artery can be severed and transferred elsewhere by microvascular anastomosis.

Question 43

b) List ways the surgeon can maximize survival of axial pattern flaps before during and after creation

Answer 43

Planning and marking is very important when performing axial pattern grafts. The body/limbs must be positioned in a relaxed position, the local cutaneous artery identified via local landmarks or doppler/ultrasound (Ideal) and the flap carefully marked. During the procedure the dissection must be performed deep to the dermal plexus, and ideally deep to cutaneous musculature if present. Care must be taken to avoid trauma to the cutaneous artery. Post-operative care includes preventing patient interference, controlling activity and providing light compression to minimize seromas.

Question 44

c) Name 4 axial pattern flaps used in the dog and in the cat, and for each example given, give the scenario for which they may be used.

Answer 44

• Superficial temporal Flap: ipsilateral and contralateral face and head, particularly maxillofacial defects.
• Caudal Auricular Flap (sternocleidomastoideus branches of the caudal auricular artery): ipsilateral and contralateral lesions of the face, ears and cranial neck.
• Omocervical Flap: face, head, ears, neck and shoulder and axillary defects. Can be passed through a parapharyngeal tunnel to cover oronasal defects caudal to the third pre-molar.
• Thoracodorsal Flap: more robust than omocervical, used to cover defects of the shoulder, thorax, elbow and axilla.
• Lateral thoracic Flap: similar to the thoracodorsal but smaller. Mostly used to cover the elbow.
• Superficial Brachial Flap: used to cover defects of the antebrachium and elbow;
• Cranial superficial epigastric flap: primarily used to cover sternal defects. Less versatile and robust than the caudal counterpart.
• Caudal Superficial Epigastric Flap: Used to cover defects of the abdomen, flank, prepuce, perineum, thigh and hind limbs. In cats it can extend as distal as the metatarsus.
• Deep Circumflex Iliac Flap: defects on the caudal thorax, lateral abdomen, ipsilateral flank, lateral lumbar region, medial and lateral thigh, greater trochanter and pelvic region.
• Genicular Flap: defects on the lateral and medial tibia as well as proximal tarsal region.
• Reverse saphenous conduit flap: defects below the tarsus
• Lateral caudal flap: defects of the perineum and caudodorsal trunk.

In cats, only the superficial temporal, caudal auricular, superficial cervical, thoracodorsal, caudal superficial epigastric and reverse saphenous conduit flaps have been evaluated.

Question 45

You wish to use an external skeletal fixator (ESF) to reduce and stabilize a closed, transverse mid diaphyseal tibial fracture in an eight year old retriever. Answer all parts of this question.
a) List, with a short description or diagram, the four main types of linear external skeleton fixators

Answer 45

External fixators are classified according to the number of planes occupied by the frame and the number of sides of the limb the fixator protrudes. 
Type Ia: (Unilateral, uniplanar), composed of a single bar and clamps through which pins are introduced. 
Type Ib: (unilateral, biplanar), composed of two bars located on the same side (i.e. frontal plane) with pins penetrating the bone from two different sides (i.e. craniolateral and craniomedial angles)
Type II (bilateral, uniplanar), composed of two bars on opposite sides of the limb. Further subdivided into “maximal” (all full pins) and “minimal” (full and half pins)
Type III (bilateral, biplanar), typically composed of three or more bars with pins protruding into the limb from three or more different planes.

Question 46

You wish to use an external skeletal fixator (ESF) to reduce and stabilize a closed, transverse mid diaphyseal tibial fracture in an eight year old retriever. Answer all parts of this question.
b) Indicate which type of ESF you would choose for this case. List your reasons

Answer 46

The fracture described should allow anatomic reduction and load sharing, but is located on a moderately poor biological environment (small muscle envelope) and is present in a senior dog (slower healing). I would choose a Type II “Minimal” fixator for its ease of application, strength and versatility. Depending on the progress of healing (if slow, based on radiographs) I might choose to gradually destabilize the construct by removing select pins starting with half pins.

Question 47

You wish to use an external skeletal fixator (ESF) to reduce and stabilize a closed, transverse mid diaphyseal tibial fracture in an eight year old retriever. Answer all parts of this question.
c) List ways you can maximize the pin/bone interface

Answer 47

Pin/bone interface can be maximized by pre-drilling the holes using a drill guide, taking care to drill as close to the center of the bone as possible. The pin (positive profile) should be inserted using slow RPM’s, and must engage both cis and trans cortices. The skin incision around the pin should be made large enough to prevent skin tension, and the pins must be introduced through tunnels created between muscle masses as much as possible (as opposed to through muscle).