Surgical Removal of Giant Lipomas in Dogs

Lipomas are benign tumors of adipose tissue that are common in dogs. Most lipomas are small, well circumscribed, movable, and not painful. They most commonly occur in the subcutaneous space but in rare cases can form in a body cavity such as the abdomen (Fig. 1a-c), or between large muscles such as the semimembranosis and semitendonosis (1).

Fig. 1a: Lateral abdominal radiograph in a dog with an abdominal lipoma.
Note large fat density mass in the mid to caudal abdomen.

Fig. 1b: Ventrodorsal radiograph of same dog as Fig. 1a.

Fig. 1c: Operative photograph of an abdominal lipoma in same dog as the above radiographs.

Lipomas that are large and grow between fascial planes are called infiltrative lipomas. (2,3)

Simple (not infiltrative) lipomas that are small, quiescent, and not causing pain or dysfunction are usually not treated. However, in some cases because of the sheer size and location of the lipoma, surgical resection is recommended. For example, a very large lipoma of the axilla like in the dog illustrated in this article may cause serious functional problems with the front limb.(Fig.2) 

Fig. 2: Preoperative appearance of a very large lipoma of the right axilla in this Labrador retriever

Surgical resection can be performed to allow better use of the leg and relief of discomfort. Even giant lipomas, if not infiltrative, can frequently be surgically removed. However, attention to anatomic detail and meticulous surgical technique are critical to avoid complications.

Diagnosis
Lipomas are suspected in any subcutaneous mass that is soft on palpation, movable, and well circumscribed. Fine needle aspirate samples appear grossly as oil droplets on a slide and reveal few cells microscopically. Radiographs (Fig. 1a,b) or CT scan of the mass may be indicated for very large or infiltrative lipomas that could be near or surrounding vital structures or in a body cavity.(4) 

Preoperative Considerations
Since many patients with lipomas are geriatric, appropriate preoperative evaluation would include a thorough history and physical examination, laboratory tests (CBC and serum chemistry profile) and thoracic radiographs if cardiopulmonary issues are suspected. 

Surgical Technique
After induction of general anesthesia, clip and aseptically prepare a wide field over the lipoma. Make an incision that spans the length of the lipoma. 

Fig. 3: Initial incision in the lipoma on same dog as in Fig. 2.

Using blunt and sharp dissection, define the borders of the mass and separate it from surrounding tissues. Finger dissection is usually effective in defining tissue planes and extracting the mass. When dissecting into deep tissue planes, use retractors to improve exposure and identify important structures such as large vessels and nerves. 

Fig. 4: Dissection of the lipoma in same dog as Fig. 2. The axilla artery and vein
and elements of the brachial plexus are seen at the base of the mass. 

Encapsulated lipomas will usually “peel out” well, but after removal inspect all surrounding tissues for residual lobules of lipoma. 

Fig. 5: Completed resection of the massive lipoma from the axillary space in dog from Fig. 2.

Prior to wound closure, inspect the surgical field for hemorrhage. Since removal of lipomas results in large areas of empty space in the tissues, place a closed suction drain to prevent fluid accumulation and seroma. (See Veterinary Key Points blog on the Jackson-Pratt drain.) 

Fig. 6: A closed suction drain has been placed in the Labrador in Fig. 2
and the incision closed routinely.

Close the wound routinely and place a light bandage on the animal to protect the drain tubing and reservoir. Leave the drain in place until drainage has reduced to trivial amounts. 

In the following video see dissection of a massive lipoma from the lateral cervical region of a dog. Removal of the mass exposed the trachea, carotid artery, and vagosympathetic trunk. 

Prognosis
Simple lipomas, even large ones, have a good prognosis since they are benign and slow growing. Postoperative recurrence is rare, but careful monitoring for development of new lipomas in other parts of the body is advised. Liposuction removal of lipomas was reportedly successful in 1 study but complications were common and recurrence of lipoma was high (28%) (5)

Infiltrative lipomas have a more guarded prognosis because they can be difficult to completely excise and recurrence is more common than with simple lipomas. Depending on the clinical study, one-third to one-half of dogs with infiltrative lipoma will develop recurrence after surgical removal. (2,3) Carefully monitor the surgical area for evidence of regrowth that can occur months or years postoperatively.

References
1. Thomson MJ, Withrow SJ, Dernell WS, Powers BE Intermuscular lipomas of the thigh region in dogs: 11 cases. J Am Anim Hosp Assoc. 1999 Mar-Apr;35(2):165-7.
2. McChesney AE, Stephens LC, Lebel J, Snyder S, Ferguson HR. Infiltrative lipoma in dogs.Vet Pathol. 1980 May;17(3):316-22
3.Bergman PJ1, Withrow SJ, Straw RC, Powers BE. Infiltrative lipoma in dogs: 16 cases (1981-1992) J Am Vet Med Assoc. 1994 Jul 15;205(2):322-4.
4. McEntee MC1, Thrall DE. Computed tomographic imaging of infiltrative lipoma in 22 dogs.Vet Radiol Ultrasound. 2001 May-Jun;42(3):221-5
5. Hunt GB1, Wong J, Kuan S. Liposuction for removal of lipomas in 20 dogs. J Small Anim Pract. 2011 Aug;52(8):419-25. 

Splenectomy in Dogs and Cats: Indications, Surgical Technique, and Postoperative Care

Splenectomy is the partial or total removal of the spleen. Common indications for splenectomy include splenic neoplasia, severe splenic trauma and splenic torsion.
(Fig 1)

Fig. 1: Abdominal exploratory revealing a very large splenic hematoma in a golden retriever.
The tumor and spleen were surgically removed.

 Thrombosis of the spleen can also occur, sometimes associated with gastric dilatation/volvulus, and also requires splenectomy. (Fig 2 )

Fig. 2: Thrombosis of part of the spleen in a dog. (normal spleen white arrow,
thrombotic spleen black arrow) Note sharp demarcation between the normal and
abnormal portions of spleen.

Preoperative Considerations

History and Physical Examination– Animals requiring splenectomy can present with a variety of clinical signs depending on the disorder. Acute onset of pale mucous membranes, collapse and hemoabdomen are common findings in animals with splenic neoplasia, especially hemangiosarcoma. For splenic fracture, there is usually a recent history of blunt or penetrating trauma. Animals with splenic rupture will have hemoabdomen and develop pale mucous membranes, collapse, tachycardia, tachypnea, and evidence of fluid on abdominal palpation. Abdominal palpation may also reveal abdominal discomfort or a cranial abdominal mass.

Diagnostic Evaluation – A complete blood count (including platelet count), biochemical profile and urinalysis are indicated in animals with suspected splenic disease. Assessment of coagulation may also be indicated, especially in dogs with suspected hemangiosarcoma since disseminated intravascular coagulation can occur with that neoplasm. Arterial blood pressure is performed to detect hypotension. Abdominal radiographs or ultrasonography may discover fluid or a cranial abdominal mass. Ultrasonography may also reveal evidence of metastasis of the primary splenic tumor to other sites such as the liver and regional lymph nodes. If fluid is present, perform abdominocentesis, and evaluate the fluid packed cell volume, total protein and cytology. Obtain thoracic radiographs to examine for metastasis or other problems.

Initial Treatment – Prior to anesthesia and surgery, stabilize patients with intravenous fluids and blood transfusions if necessary. Although it may be impossible to return the animal to normal circulatory status prior to surgery, improvement of their condition is desirable to make them a better candidate for anesthesia and surgery.

Surgical Anatomy 

The spleen is located in the left cranial abdomen and lies parallel to the greater curvature of the stomach. The splenic artery is a branch of the celiac artery. Branches of the splenic artery also supply the left limb of the pancreas (pancreatic branch), the fundus of the stomach (short gastric arteries and veins), and the greater curvature of the stomach (left gastroepiploic artery and vein). (Fig 3) Many small branches arise from the terminal branches of the splenic artery and vein and enter the splenic parenchyma perpendicular to the long axis of the spleen. The splenic vein drains the spleen and transports blood into the gastrosplenic vein and ultimately to the portal vein.

Fig. 3: Surgical anatomy of the spleen. Arrows indicate the small vessels that
are dissected, ligated in small groups, and divided during total splenectomy.
(from: Evans HE, de Lahunta Miller's Anatomy of the Dog Saunders/Elsevier 4th ed.
Tobia and Johnston, Veterinary Surgery Small Animal Elsevier, 2012)

Surgical Technique

Perform a routine ventral abdominal approach from the xyphoid to a few centimeters cranial to the pubis. After a thorough exploratory of the abdomen, the spleen is exteriorized and isolated with moistened abdominal sponges. A partial or total splenectomy can be performed, depending on the reason for the splenectomy. Partial splenectomy will preserve splenic function, but total splenectomy is usually performed since it is technically easier and there are few long-term complications from total splenectomy in dogs and cats.

If one or more tumors are present on the spleen, omental adhesions may be present and should be ligated and sharply divided. Dissection and ligation of the small splenic vessels close to the hilus can then be done. These vessels can be ligated and divided in small groups when they are close together. Be careful to preserve the short gastric vessels that supply the gastric fundus, and the left gastroepiploic vessel that supplies blood to the greater curvature of the stomach. Also avoid ligating the pancreatic branch of the splenic artery. If the small vessels are ligated close to the splenic parenchyma, vessels to the pancreas and stomach will not be compromised.

Splenic vessels can be ligated with suture (e.g. Monocryl), hemostatic clips; the LDS  device (ligate, divide, staple), or the Ligasure vessel-sealing device (see video below). The author prefers the Ligasure for splenectomy since it is a rapid and effective means of providing hemostasis.

In animals with splenic torsion, the blood vessels to the spleen are twisted into a pedicle that contains the mesentery and vessels. Do not untwist the spleen since this will allow cellular breakdown products, thrombi, and other toxic substances to be released into circulation.(1) Ligate the entire vascular pedicle with full and transfixing ligatures and remove the spleen.

After removal of the spleen, check all ligated vessels for lack of persistent hemorrhage and then close the abdomen routinely.

Postoperative Care and Complications

Maintain supportive care immediately after surgery consisting of intravenous fluids, analgesics and monitoring of vital signs. If preoperative or intraoperative blood loss was excessive monitor the animal’s PCV postoperatively and consider blood transfusion if the PCV drops below 20. With appropriate care most dogs will recover from splenectomy quickly with many being discharged from the hospital the day after surgery.

The most common complication associated with splenectomy is hemorrhage. Other potential complications include pancreatitis, cardiac arrhythmias, and postoperative pain.

The prognosis for dogs undergoing splenectomy varies depending on the splenic disease. Dogs and cats with splenic trauma, splenic torsion, or benign neoplasia have a good prognosis assuming they survive the perioperative period. In contrast, animals with malignant neoplasia, most commonly hemangiosarcoma, have a poor prognosis due to the tendency for metastasis of the primary tumor.(2)

References

1. Richter MC. Spleen, in Veterinary Surgery: Small Animal, eds. KM Tobias, SA Johnston, Elsevier, St. Louis, 2012, pg. 1341.
2. Spangler WL1, Kass PH. Pathologic factors affecting postsplenectomy survival in dogs. J Vet Intern Med. 1997 May-Jun;11(3):166-71.

Complete Surgical Excision of Mast Cell Tumor in Dogs and Cats

A wide variety of skin tumors occur in dogs and cats, both benign and malignant.  An important principle of surgical management of these tumors is to establish a diagnosis before the operation.  Fine needle aspiration (FNA) is a practical and reasonably accurate method to biopsy skin masses, and the results allow clinicians to plan appropriate treatments.  For example, benign skin tumors such as epidermal inclusion cysts require only a marginal excision and routine skin closure.  Malignant skin tumors, such as mast cell tumor (MCT), require extensive tissue resection (e.g. removal of 2-3 cm of normal tissue with the mass) followed by more complicated reconstruction in some cases.  An adequate deep margin of normal tissue should be removed with the tumor as well as medial and lateral margins. Excise a section of the tissue layer below the tumor to achieve a complete resection. If the tumor is located in the subcutaneous space remove the muscle or deep fascia below the tumor.

Preoperative Considerations

As is true for any animal with neoplasia, tumor staging is done prior to surgery to establish the extent of disease. Appropriate imaging, such as thoracic radiographs and abdominal ultrasound, is used to examine for metastasis or other unrelated problems. Also carefully examine regional lymph nodes and if enlarged perform FNA. With MCT, administer preoperative antihistamines such as diphenhdyramine to reduce the inflammation associated with histamine release by the tumor. The drug can be given either orally for 1 or more days preoperatively, or parenterally just before surgery. Avoid excessive manipulation of the tumor before surgery to prevent degranulation of mast cells and release of histamine.

Be sure to warn owners about potential complications of surgical removal of MCT. Even with antihistamine pre-treatment wound complications such as excessive inflammation, seroma, and dehiscence are possible.

Surgical Technique

After placing the dog or cat under general anesthesia, perform a wide aseptic preparation of the surgical site. (Fig 1) 

Fig. 1: Cutaneous mast cell tumor (circle) over the dorsal thoracic area in a spaniel.
(note Figs 3-7 are the same dog as in this picture)

Use a sterile ruler and marking pen to delineate the mass (Fig 2), then draw a circle around the tumor that is 2-3 cm from the edge of the mass.(Fig 3)

Fig. 2: Sterile surgical marking pen and ruler to map surgical margins around skin tumors.

Fig. 3: MCT (inner circle and X) delineated by an outer circle of 2cm margins of normal skin

Draw lines that taper the incision on each end to make the incision an ellipse and thus avoid having “dog ears” of skin on the ends.(Fig. 3) Be sure that the long axis of the resultant incision is parallel to the tension lines in that area of the body.

Make the incisions on the proposed lines and continue the dissection into the deep tissues. Avoid dissecting toward the tumor; as you proceed deeper in the tissues continue to honor the 2 or 3 cm margin originally mapped on the skin. Once the desired layer of deep margin has been reached, incise the fascia or muscle, lift the tumor and associated tissue (en bloc), and dissect the block of tissue completely free.(Fig. 4)

Fig. 4: Intraoperative picture with skin mass and underlying tissue
being removed from right to left. Note underlying muscle being removed with the mass.

Wide excision of skin or subcutaneous masses frequently leaves large skin defects that can be difficult to close. When primary closure cannot be obtained due to excessive skin tension, consider either immediate or staged flap or graft reconstruction. (see blogs from 3/20/14 on punch skin grafts and 4/1/14 on axial pattern skin flaps) If local tissues are adequate for closure, use the “Rule of Halves” technique (see blog from 11/3/14 on closure of elliptical skin incisions). A towel clamp can be used to initially bring the skin together at the middle of the incision to make suture placement easier.(Fig. 5) 

Fig. 5: A towel clamp is used to temporarily relieve tension and allow
suture closure the incision.

Close deep tissues at the middle of the incision first, then continue to place sutures in the rule of halves manner to achieve complete closure.(Fig. 6, 7)  

Fig. 6: Deep sutures have been placed in the middle of the incision; the next 2 deep sutures
will be placed at the arrows in the "Rule of Halves" manner.

Fig. 7: Final appearance of closed incision

Place a closed suction drain if excessive dead space exists in the deep tissue layers that cannot be closed (see blog from 3/15/14 on Jackson Pratt drains)

After removal of the mass, ink the tissue specimen with appropriate dye such as India ink to allow the pathologist to identify the margins of the excision. Also, place a suture on either the cranial or caudal aspect of the specimen to further orient the pathologist in case one of the margins shows incomplete excision of the tumor.

Postoperative Care

Routine supportive care is administered after removal of mast cell tumors. Avoid NSAIDS administration on MCT dogs to prevent compounding the gastric irritation from the histamine. Tramadol is a good alternative postoperative analgesic. Monitor the surgical incision for swelling or bleeding, and instruct owners to limit exercise and monitor the surgical site carefully at home. Although most dogs and cats recover without major systemic complications after removal of MCT, systemic vascular collapse is possible from massive histamine release in rare cases. Fluid resuscitation and corticosteroid administration may be necessary to support and stabilize the patient if this occurs.

Prognosis

Long-term outcome is dependent upon the histopathologic classification of the MCT. There are 2 major classification schemes now used by pathologists, i.e., Grade 1, 2 and 3 (1 is low grade, 3 is high grade and 2 is intermediate grade) or a simpler 2 tier system of low-grade vs. high grade.(1) Regardless of the system used, the higher the grade of MCT the poorer the prognosis.(1,2) Information on adjunctive therapy such as chemotherapy or radiation therapy is readily available and may be useful in animals with incompletely excised or metastatic tumors.(3)

References

1. Sabattini S, Scarpa F, Berlato D, Bettini G. Histologic grading of canine mast cell tumor: is 2 better than 3? Vet Pathol. 2015 Jan;52(1):70-3.

2. Donnelly L, Mullin C, Balko J, et.al. Evaluation of histological grade and histologically tumour-free margins as predictors of local recurrence in completely excised canine mast cell tumours.Vet Comp Oncol. 2015 Mar;13(1):70-6.

3. London CA, Thamm DH. Mast cell tumor. In: Small Animal Clinical Oncology, eds: Withrow S, MacEwen G, Elsevier, 2013, pg. 335.

Thyroid Cancer in Dogs: Not always a bad disease!

Thyroid neoplasia is fairly common in dogs and is seen more frequently in boxers, golden retrievers, and beagles.(1) The tumors are usually malignant and unilateral however bilateral tumors are possible. Carcinoma is the most common tumor and they can metastasize to lungs and regional lymph nodes.(2) They can also be locally invasive and spread into adjacent vasculature such as the jugular vein. Because of the complex nature of the cervical anatomy and potential invasiveness of thyroid tumors, surgical removal by a board certified veterinary surgeon is recommended.

Clinical Signs

Dogs may be minimally symptomatic and present for a mass in the neck that is either discovered by the owner or found on routine physical examination.(Fig. 1) 

Fig. 1: A West Highland White Terrier with a thyroid  tumor visible in the neck. (arrows)

If early diagnosis is pursued, the tumor may be small, encapsulated, and freely movable in the neck. More advanced tumors can be very large, fixed in position, and encompassing the trachea and larynx.

In rare cases the thyroid tumor is functional and secreting an excessive amount of thyroxine causing hyperthyroidism. Signs of hyperthyroidism include weight loss, increased appetite, polyuria and polydipsia. Cardiac abnormalities such as cardiomyopathy can result from the excessive thyroid hormone secretion. Submit blood samples for thyroid hormone panel to confirm the diagnosis of a functional thyroid tumor.

Diagnosis and Staging

An accurate preoperative diagnosis is important since masses in the neck other than thyroid tumors, such as those involving the salivary glands or lymph nodes, can occur. Carefully palpate the neck mass and regional lymph nodes. Small, well-circumscribed and freely movable tumors are usually amenable to surgical resection.

Fine-needle aspirate or tissue biopsy of the thyroid tumor helps establish the type of tumor. However, recognize that bleeding associated with these procedures can obscure the surgical field and make the procedure more difficult. Ultrasound examination may be helpful to identify the involved thyroid lobes, evaluate for local tissue invasion, and guide fine needle aspiration. Obtain thoracic radiographs to rule out pulmonary metastasis or other cardiopulmonary disorders.

Surgical Procedure

The objectives of surgery are to: completely remove the thyroid mass, preserve at least one parathyroid gland, minimize blood loss, and avoid injury to the recurrent laryngeal nerves, trachea, and esophagus.

Anatomy

The thyroid gland in the dog is divided into 2 lobes that are located adjacent to the trachea and just distal to the larynx.(3) (Fig. 2) 

Fig. 2: Normal anatomy of the cervical region in the dog. Arrows delineate the thyroid lobes.
(Illustration by Mr. Tim Vogt, Medical Illustrator, College of Veterinary Medicine, The Ohio State University)

The normal gland has a pale brown color and is approximately 2 to 2 and 1/2 cm in length.  The principle blood supply to each lobe is the cranial and caudal thyroid arteries, branches of the common carotid artery.  Venous drainage of the thyroid is via the cranial and caudal thyroid veins.

The thyroid gland has a distinct capsule that can be bluntly separated from the parenchyma.  Small blood vessels may be located on the capsule surface and between the capsule and the parenchyma of the gland. Two parathyroid glands are usually associated with each thyroid lobe.  The external parathyroid gland usually lies in the fascia at the cranial pole of the thyroid lobe.  The internal parathyroid gland is usually embedded in the thyroid parenchyma and is variable in location.  The external parathyroid glands are much smaller than the thyroid lobe and can be distinguished from the thyroid tissue by their lighter color and spherical shape. However, the parathyroid gland can be confused with fat.  The blood supply to the parathyroid glands also arises from the cranial thyroid artery.

Overview of Surgical Technique

The dog is placed in dorsal recumbency and the ventral cervical area prepared for aseptic surgery. A ventral midline cervical surgical approach is made from the larynx to the manubrium. The paired sternohyoideus muscles are divided on the midline and retracted. (Fig. 3) A stomach tube or small endotracheal tube in the esophagus helps identify this structure.

Fig. 3: Operative photograph of a unilateral thyroid tumor (arrows)
in a dog with thyroid carcinoma.

Ligate or cauterize the extensive vascular network surrounding the thyroid and carefully dissect out the tumor. Begin dissection at the caudal aspect of the tumor and gradually work cranially. (Fig. 4) 

Fig. 4: Dissection of a thyroid carcinoma in a dog proceeding from
caudal to cranial (black arrow). Yellow arrows indicate the trachea.

Identify the recurrent laryngeal nerves adjacent to the trachea and avoid trauma to them. If possible, identify and preserve the parathyroid glands especially with bilateral thyroidectomy. With large malignant tumors, the parathyroid glands may be difficult to indentify.

Close the muscle routinely with simple continuous, absorbable suture; the subcutaneous tissue with simple continuous, absorbable suture; and the skin with simple interrupted, nonabsorbable suture or an intradermal pattern using absorbable suture.

Postoperative Care and Complications

Short-Term

Closely monitor for hemorrhage or seroma formation at the surgical site. Cold compresses on the incision for the first 24 hours are helpful to prevent swelling.Monitor serum calcium concentrations for at least 2–4 days postoperatively if a bilateral thyroidectomy was performed. Monitor the calcium concentrations longer if the levels are decreasing. Treat hypocalcemia with oral calcium and vitamin D. If bilateral thryoidectomy was performed, evaluate thyroid function and treat hypoparathyroidism if necessary.

Long-Term

Reevaluate the dog frequently (every 3 months for the first year) with physical examinations and thoracic radiographs to monitor for recurrence of the primary tumor and metastasis.
Consider postoperative chemotherapy or radiation therapy if the tumor was malignant and incompletely excised.

Prognosis

Key Point:  Surgical resection of encapsulated, movable thyroid tumor in dogs has been found to result in median postoperative survival of 20 months.

In the study cited above the dogs were treated with surgery alone and had no evidence of metastasis at the time of surgery.(4) As with most cancers, early diagnosis and treatment increases the chances of a good outcome.

References
  1. Birchard SJ, Roesel OF: Neoplasia of the thyroid gland in the dog: A retrospective study of 16 cases. JAAHA 17:369-372, 1981.
  2. Brodey TS, Kelly DF: Thyroid neoplasms in the dog. Cancer 22: 406-416, 1968.
  3. Evans HE, Christensen GC: Miller's Anatomy of the Dog, The Endocrine System, WB Saunders, Philadelphia, 1979, pp. 611-618.
  4. Klein MK1, Powers BE, Withrow SJ, Curtis CR, Straw RC, Ogilvie GK, Dickinson KL, Cooper MF, Baier M. Treatment of thyroid carcinoma in dogs by surgical resection alone: 20 cases (1981-1989).J Am Vet Med Assoc. 1995 Apr 1;206(7):1007-9.

Does Spay or Neuter Make Dogs Overweight?

Lefebvre SL1, Yang M, Wang M, Elliott DA, Buff PR, Lund EM.

Effect of age at gonadectomy on the probability of dogs becoming overweight.

J Am Vet Med Assoc. 2013 Jul 15;243(2):236-43.

Summary

The authors of the above study compared 1,930 dogs that were spayed or neutered (gonadectomy) to 1,669 sexually in tact dogs to evaluate the tendency of the spayed or neutered dogs to become overweight.  They also looked at the effect of age at the time of gonadectomy to see if that had an effect on becoming overweight. All dogs were patients at Banfield Pet Hospitals, giving the authors a consistent data retrieval system. Follow-up on all animals was for a period of greater than or equal to 10 years.

The authors found that spayed or neutered dogs were statistically more likely to become overweight compared to sexually in tact dogs.  However, this was found only for the first 2 years after the spay or neuter. Age at gonadectomy and sex of the dog did not affect the tendency to become overweight.

An additional interesting finding in the study was that both groups of dogs (gonadectomy vs. sexually in tact) had a surprisingly high percentage of overweight individuals. In the sexually in tact dogs, 37% became overweight over time, and in the gonadectomized dogs, 66% became overweight. Also, large breed dogs were more likely to become overweight in this study.

Commentary

This was a well-designed and executed study of a large population of dogs. The diagnosis of being overweight seemed arbitrary since no objective criteria were used other than body condition scores, but veterinarians performing routine examinations of the dogs were the ones making the overweight diagnosis.

Looking at the entire group of dogs (3,599), over half of them were diagnosed as being overweight. Beyond the effect of gonadectomy, this study illustrates the larger problem of obesity in pets. Whether being fed too much, or exercising too little, a high proportion of pets in the US are at an unhealthy weight which is likely affecting their quality of life and resulting in secondary health problems. More research is needed to investigate the causes of obesity in pets and how it can be effectively managed.

What are your thoughts about this study and about the more global problem of pet obesity? Post comments either here or on facebook (Dr. Stephen Birchard, Veterinary Continuing Education).

Total Ear Canal Ablation in Dogs and Cats: A big surgery with big benefits.

Total ear canal ablation is removal of the entire ear canal. Indications for TECA include severe chronic otitis with obstruction of the canal, ear canal or middle ear neoplasia, severe trauma to the ear canal, or congenital abnormality that causes obstruction of the canal.

Key Point: Chronic proliferative otitis can result in calcification of the ear canal. This is an irreversible, end stage change in the ear that can only be resolved by TECA.

TECA is combined with a lateral bulla osteotomy (BO) to remove residual epithelium and debris from the middle ear after the ear canal is removed. Because of the prevalence of severe ear canal disease in dogs and cats, TECA/BO has become a common surgical procedure. However, a properly performed TECA/BO is a difficult procedure and can be associated with many complications. It should be performed by a board certified surgeon who is familiar with the anatomy of the ear and the technical aspects of the procedure. However, a well performed TECA can significantly improve quality of life of animals with ear disease.

Anatomy

The entrance of ear canal, the external acoustic meatus, is surrounded by several cartilaginous structures including the tragus, antitragus, helix, and antihelix. The external ear canal in dogs and cats is divided into vertical and horizontal portions. (Fig. 1) 

Fig 1: Cross section of the ear canal in a dog.
(from: Smeak DD. Surgery of the ear canal and pinna. Saunders Manual of Small Animal Practice, 3rd ed., 
Birchard and Sherding editors, Elsevier, 2006)

The auricular cartilage is the vertical portion of the canal. The annular cartilage is located where the vertical canal turns into the horizontal canal. (Fig. 1)

The epidermal lining of the ear canal is rich in sebaceous and apocrine glands. In dogs with chronic otitis externa, an epithelial pouch may develop just adjacent and ventral to the tympanic bulla. (Fig. 2) 

Fig 2: Cross section of the ear in a dog with chronic otitis. Note the epithelial pouch
that develops in the canal adjacent to the entrance to the tympanic bulla. The tissue
colored red indicates that removed during a TECA/BO
(from: Smeak DD. Surgery of the ear canal and pinna. Saunders Manual of Small Animal Practice, 3rd ed.,
Birchard and Sherding editors, Elsevier, 2006)

The V-shaped parotid salivary gland lies over the ventro-lateral aspect of the vertical ear canal.

The middle ear is located in the petrous temporal bone. (Fig. 2) The tympanic bulla is the ventral wall of the tympanic cavity. It is an air-filled cavity just medial to the tympanic membrane. In the cat a septum divides the bulla into dorsomedial and ventrolateral compartments. Sympathetic nerve fibers run through the middle ear, and adjacent to the tympanic bulla are the facial nerve ventrolaterally, the carotid artery medially, and the hypoglossal nerve ventrally.

The major blood supply to the ear is via the great auricular artery and vein. Another important regional structure is the facial nerve. The nerve exits the skull just caudal to the ear canal and courses ventrally below the canal, then cranially. (Fig. 3) 

Fig. 3: Anatomy of important structures associated with the ear canal.
(from: Smeak DD. Surgery of the ear canal and pinna. Saunders Manual of Small Animal Practice, 3rd ed.,
Birchard and Sherding editors, Elsevier, 2006)

The nerve is motor to the lips and eyelids, therefore trauma to it causes lip droop and inability to blink.

Preoperative Considerations

Besides routine preoperative diagnostics such as history, physical examination, and blood tests, a good otoscopic exam and diagnostic imaging should be obtained on animals being considered for ear canal ablation.  Foreign bodies, neoplasia, or obstructive disorders of the canal may be discovered on otoscopic exam. Animals with tumors should also be screened for metastatic disease with thoracic radiographs, fine needle aspirate of regional lymph nodes if enlarged, and other tests as indicated. Skull radiographs or CT scan is usually recommended before TECA/BO to assess the tympanic bulla. See Veterinary Key Points blog “Nasopharyngeal Polyps in Cats”, 4/15/2015 for more discussion of bulla imaging techniques.

Surgical Procedure                      

After making the initial incisions around the external acoustic meatus and then ventrally along the vertical canal, carefully dissect the ear canal from surrounding tissues. (Fig. 4)

Fig. 4: Initial dissection in a canine cadaver for a TECA/BO. (note: Figures 4,5,7, and 8 are cadaver specimens.
 The cartilage around the external acoustic meatus has been severed 
and lifted up to allow dissection down the canal.

Dissect soft tissues close to the canal to avoid trauma to important structures, such as the facial nerve. (Fig. 5) 

Fig. 5: Continued dissection of the canal exposing the facial nerve in the stay suture. (arrow)

In ossified canals the facial nerve may be imbedded in the outer layer of the ear canal. (Fig. 6)

Fig. 6: The facial nerve (surrounded by yellow vessel loops) is being released from its adherence
to the ossified ear canal (arrow). Note the groove left in the canal by the nerve after gently dissecting it off.

 After removal of the canal using scalpel or scissors, carefully remove any remnants of canal and epithelium from the typanic bulla. Perform a bulla osteotomy with rongeurs to better expose the interior of the bulla. (Fig. 7) 

Fig. 7: After removal of the canal, the tympanic bulla is exposed by removing some of the
lateral aspect of the bony wall with rongeurs. Any remnants of the ear canal attached to the bulla
can also be removed with the rongeurs

Use a bone curette to remove epithelium and debris from the interior of the tympanic bulla. (Fig. 8) 

Fig. 8: Curettage of the interior of the bulla with a bone curette.

Avoid curettage of the dorsal aspect of the bulla to prevent trauma to the structures of the inner ear. Submit samples of fluid or debris from the tympanic bulla for culture and sensitivity. Also, submit the ear canal for histopathology to rule out neoplasia. Flush the incision with warm, sterile saline prior to closure. Close the incision in a “T” shape in multiple layers: deep fascia, subcutaneous tissue, and skin.

Postoperative Care and Complications

Postoperatively, protect the incision with a light bandage or Elizabethan collar. Administer analgesics for at least 3-5 days postoperatively. Long-term antibiotics (i.e. 3-4 weeks) are indicated in animals with bacterial infections. Choose antibiotics based upon the results of culture and sensitivity. If the animal’s eyelid motor function is decreased due to facial nerve injury, keep the eye lubricated with eye ointments or drops (e.g. Duratears) administered every 4-6 hours to prevent corneal ulcers until facial nerve function returns. 

Complications of TECA include acute pharyngeal edema, facial nerve damage, wound infection or dehiscence, Horner's syndrome, or deep abscesses. Deep abscesses occur due to leaving small amounts of secretory epithelium in or around the tympanic bulla. Reoperation to retrieve the residual epithelial tissue is usually necessary. Depending on the study, facial nerve deficits after TECA/BO in dogs can range from 36 to 48%, and in cats as high as 56%.(1-3) Although hearing is certainly diminished, some studies have found that some ability to hear is preserved even after removal of the ear canal.(2)

References

1. DD Smeak, WD DeHoff. Total Ear Canal Ablation Clinical Results in the Dog and Cat. Veterinary Surgery Volume 15, Issue 2, pages 161–170, March 1986
2. R. A. S. White, C. J. Pomeroy. Total ear canal ablation and lateral bulla osteotomy in the dog  Journal of Small Animal Practice Volume 31, Issue 11, pages 547–553, November 1990
3. Rebecca E. Spivack, A. Derrell Elkins, George E. Moore, and Gary C. Lantz (2013) Postoperative Complications Following TECA-LBO in the Dog and Cat. Journal of the American Animal Hospital Association: May/June 2013, Vol. 49, No. 3, pp. 160-168