Author

Stephen J. Birchard DVM, MS, Diplomate ACVS

Sunday, September 11, 2016

Caserean Section in Dogs and Cats: Surgical Technique

Indications

Cesarian section (C-section) in dogs and cats is indicated for a variety of reasons such as uterine inertia, oversized neonates, narrowed maternal pelvic canal, and others. Fetal dystocia is common in brachycephalic breeds such as Bulldogs, prompting some breeders or owners to schedule the C-section as an elective procedure in these kinds of dogs. Evidence fetal death or uterine infection would also warrant immediate C-section. The readers are referred to other publications for more information on dystocia in dogs and cats.(1)

Cesarian section is a safe surgical procedure and one study found fetal survival actually slightly higher with C-section than natural birth.(2) For information on pre-operative assessment and anesthesia for C-section see Veterinary Key Points blog by Dr. Lisa Ebner posted June 14, 2016.

Surgical Procedure

The abdomen is clipped and an initial scrub performed prior to beginning anesthesia. This minimizes the time spent under anesthesia helping to prevent depression of the puppies or kittens. Perform other pre-operative and anesthestic protocol as described in the Veterinary Key Points blog by Dr. Lisa Ebner posted June 14, 2016 on anesthesia for C-section.

Place the animal in dorsal recumbancy and perform a routine ventral abdominal midline approach. Be careful to avoid trauma to the enlarged uterus when entering the peritoneal cavity. Exteriorize the entire uterus including both uterine horns. (Fig. 1) This simple step is important to relieve pressure on the caudal vena cava by the very enlarged uterus and therefore improve venous return to the heart. Isolate the uterus from the peritoneal cavity with moistened abdominal sponges.
Fig. 1: Gravid uterus exteriorized from the abdominal cavity
Make an incision in the ventral aspect of the uterine body just proximal to the bifurcation of the horns.(3)  Take care to avoid trauma to the puppies inside the uterus. Once inside the uterine lumen, carefully begin removing puppies one by one.(Fig. 2)
Fig. 2: Begin removing puppies from the incision in the uterine body midline.
fromSicard GK, Fingland RB. Surgery of the ovaries and uterus. In: Saunders Manual of Small Animal Practice, 3rd edition, Birchard SJ, Sherding RG, eds. Elsevier, St. Louis, 2006
Begin with puppies in the uterine body, then milk them down each horn to the incision and then remove. The uterine incision may have to be extended into the horns to reach and remove all puppies.

When each puppy is removed from the uterus, gently tear the placental membrane and remove it from the fetus.(Fig. 3) 
Fig. 3: After removing puppy from the uterus gently open and peel away placental membranes
from: Sicard GK, Fingland RB. Surgery of the ovaries and uterus. In: Saunders Manual of Small Animal Practice, 3rd edition, Birchard SJ, Sherding RG, eds. Elsevier, St. Louis, 2006

Take care to avoid spillage of fluids into the peritoneal cavity. A convenient area to perforate the thin membrane is at the ventral neck of the puppy. Once the membrane has been removed, place 2 small hemostatic forceps on the umbilical cord, transect the cord between the clamps, and hand the puppy off to an assistant.(Fig.4 ) 
Fig. 4: After removing placental membranes from the puppy, double clamp
the umbilical cord with small hemostats, cut between them, and pass the
puppy off to an assistant.
The assistant will then ligate the cord with absorbable suture and begin routine care to stimulate respirations and assessment (see Veterinary Key Points blog by Dr. Lisa Ebner posted June 14, 2016).

Before uterine closure, be sure to check the entire uterus including the body and vagina for any remaining fetuses. Routine ovariohysterectomy can be performed now if requested by the owner. If the uterus is to be preserved, close the uterine incision with absorbable suture (Monocryl or PDS) in a Cushing pattern.  Lavage the abdomen with warm sterile saline if spillage of uterine contents has occurred into the peritoneal cavity. Close the abdominal incision routinely. Intradermal closure of the skin layer is preferred to avoid the irritation associated with skin sutures and nursing puppies.

Postoperative Care

When the bitch is fully recovered from anesthesia the puppies can be placed with her and encouraged to nurse. Carefully monitor the puppies and bitch to be sure she does not accidentally injure the pups. Soon after anesthetic recovery is it usually best to discharge the dog and her puppies back to the home and educate the owner on care of the bitch and puppies. See blog on C-section anesthesia for postoperative analgesia of the mother.

References

1. Graves T. Diseases of the ovaries and uterus. In: Saunders Manual of Small Animal Practice, 3rd edition, Birchard SJ, Sherding RG, eds. Elsevier, St. Louis, 2006, pgs. 987-991.
2. Moon PF, Erb HN, Ludders JW, Gleed RD, Pascoe PJ Perioperative management and mortality rates of dogs undergoing cesarean section in the United States and Canada
JAVMA [1998, 213(3):365-369
3. Sicard GK, Fingland RB. Surgery of the ovaries and uterus. In: Saunders Manual of Small Animal Practice, 3rd edition, Birchard SJ, Sherding RG, eds. Elsevier, St. Louis, 2006, pgs. 996-999.

Tuesday, June 14, 2016

Anesthesia for Cesarian Section in Dogs and Cats: Dr. Lisa Ebner, DACVAA

Cesarean section (c-section) is a commonly performed surgical procedure in small animal practice. In the first segment of this 2-part blog on c-section, anesthetic management of the pregnant bitch or queen is presented by board certified anesthesiologist Dr. Lisa Ebner. In the 2nd segment we will focus on surgical management. The readers are referred to other publications for material on diagnosis and medical treatment of dystocia in small animals.            

As with any anesthesia and surgery the primary goal is to induce and maintain a surgical plane of anesthesia to eliminate pain and allow a safe recovery of the animal upon completion of the procedure. In Cesarean section the neonates complicate the anesthetic management. Anesthetic protocols must consider the health and well being of the unborn puppies and kittens as well as the mother.

With a planned c-section, the gestation length is known, the patient has been properly fasted, and the procedure takes place during normal business hours when plenty of staff members are available to assist.  This contrasts with the emergency c-section where often the patient has been straining for hours, may be in a compromised metabolic state and the viability of the puppies may be compromised. In clinical studies both maternal and puppy mortality was significantly increased with emergency compared to planned c-sections (1,2).

Pre-anesthetic Considerations
Anesthesia planning begins with assessment of patient risk. Obtain a thorough history that includes any concurrent medical conditions and medications.  Determine how long the bitch has been in labor and if any puppies, dead or alive, have been delivered.  A thorough physical exam is important and diagnostic imaging, such as abdominal ultrasound or radiographs, is very helpful. (Fig. 1) 
Fig. 1: Lateral radiograph of late term pregnancy in a dog.

Abdominal ultrasound is more sensitive in detecting fetal viability; while abdominal radiographs help determine the number, size, and position of the fetuses.  If possible, assessment of fetal heart rate can be a good indicator of a healthy (150-220 bpm) vs. a stressed fetus (100-150 bpm).  Laboratory evaluation of the bitch or queen is also indicated.  Selection of lab tests will depend on patient assessment, but a minimum database of PCV, total solids, BUN, glucose, ionized calcium, and other electrolytes prior to anesthesia is recommended. 

Physiologic Changes With Pregnancy
Pregnancy causes significant alterations in the mother’s physiology that need to be considered. Due to higher plasma volume in relation to the number of RBCs present, the pregnant bitch or queen has a “relative” anemia. Therefore if the PCV is within the normal range then she may actually be dehydrated. Pain or catecholamine release can cause tachycardia and increased cardiac output.  Compression of the great vessels in the abdomen during pregnancy does not appear to have the same potential in animals as it does in humans.  Based on clinical studies, small dogs under 25 kg do not appear to exhibit postural influences on systemic blood pressure but large breed, full term bitches could have the potential for a decrease in blood flow to the uterus (3,4). This effect may be exaggerated in animals that are dehydrated or have other illness affecting their cardiopulmonary system. The gravid uterus also displaces the diaphragm cranially, leading to a decreased tidal volume in the patient.  Hyperventilation may also be present due to pain and distress in a patient presenting for a c-section.  Overall there is an increased need for oxygen coupled with lower functional residual capacity that ultimately can result in hypoxemia. 

Anesthesia Protocol
Before beginning anesthesia consider administering 3 to 5 minutes of pre-oxygenation with 100% O2 provided by a tight-fitting oxygen mask (as long as this does not cause undo stress to the animal).  Hypocalcemia may be present in small breed dogs, dogs with large litters, or with uterine inertia. This abnormality should be corrected along with any fluid deficits prior to anesthesia and surgery.

To reduce complications and depression of the neonates, anesthesia and surgery time should be as short as possible.  Clip and perform the initial scrub of the patient prior to induction of anesthesia.  The surgeon should already being scrubbed, gowned, gloved and ready to begin draping as soon as the final surgical prep has been done.  The actual time from induction of anesthesia to removal of the neonate(s) should ideally be less than 5 minutes. 

Anesthetic Drug Selection
Avoid premedication in the pregnant animal because opioids are associated with respiratory depression in the neonates and other tranquilizing or sedating drugs, such as acepromazine or alpha2 agonists, are associated with decreased vigor in the newborns.  Even though some of the premedication drugs are reversible by administration of an antagonist, it is still best to avoid then because there is an increased risk of morbidity and mortality for the neonates.

Intravenous Induction
An intravenous catheter should always be placed for administration of IV fluids and emergency drugs if needed during anesthesia.   After adequate time for pre-oxygenation, the bitch or queen can be induced with propofol IV to effect (typically 4 mg/kg) and intubated with an appropriately sized endotracheal tube that is inflated to prevent a leak at 20 cm H2O.

Inhalation Anesthetics
For anesthesia maintenance isoflurane or sevoflurane, in oxygen, is acceptable.  Ideally, the concentration of the inhalant should be kept as low as possible to prevent the animal from responding to surgical stimulation but also prevent the dose-dependent vasodilation and accompanying hypotension associated with use of inhalants. 

Local or Regional Anesthetics
In order to keep the inhalant concentration to a minimum, local-regional anesthesia is often incorporated.  A line block can be performed preoperatively and will continue to provide analgesia post-operatively.  Bupivacaine (0.5%) is often selected for the line block due to its prolonged duration of action compared to lidocaine (4 to 6 hours vs. 60-90 minutes).  However, the time to onset is slightly longer than lidocaine. 

Another technique that can be included in the anesthetic protocol is a lumbosacral epidural with lidocaine (2%).  Lidocaine is selected because the shorter duration of action is actually preferred since most patients will go home with the owner soon after recovery from anesthesia.  The volume of drug used in the epidural should be decreased about 20-25% compared to a non-pregnant patient because the epidural space is actually decreased in a pregnant patient due to increased size of epidural veins.  It is an option to add morphine to the lumbosacral epidural.  Be careful performing epidurals in animals that are hemodynamically unstable because the local anesthetic drug can have a vasodilatory effect in the epidural space, leading to hypotension.  Other contraindications for epidural include infection of the skin at the site of needle puncture, coagulopathy, and an obese patient that makes palpation of the landmarks unreliable.  Although acceptable to perform c-section with only an epidural technique, such as is done in humans and many large animals, it would depend on the comfort and experience level of the anesthetist since an incomplete block may occur and the patient could respond to surgical stimulation.  Also, the patient would not have a protected airway and is at risk for aspiration pneumonia if regurgitation occurs. 

Neonatal Care
Once the neonates are delivered have several experienced staff on hand to help resuscitate them.  Organize the personnel as well as necessary drugs and supplies prior to induction.  After delivery gently clear fluid from the oral cavity of neonates of fluid with a bulb syringe.  Do not “swing” the neonate to clear its airway, as this has been associated with intracranial trauma (5).  If not already done by the surgeon, clamp the umbilical cord with a small hemostat and place a ligature with absorbable suture around the cord. Typically the cord is dipped in povidone-iodine solution after it is transected. 

Rub the neonates with a soft, absorbent towel immediately to stimulate spontaneous ventilation. (Fig. 2) 
Fig. 2: Newborn puppy being gently rubbed with a dry towel to stimulate respirations.
If there is no sign of spontaneous breathing, administer supplemental oxygen and preferably manual breaths after endotracheal intubation (should be attempted if it can be carefully done).  Most endotracheal tubes will be too large for neonates, but removing the stylet from a 16 gauge IV catheter and using only the polyurethane flexible catheter portion is an option.  If no heart-beat can be palpated, begin gentle cardiac compressions (ideally > 180 bpm).  If the puppy or kitten is bradycardic, this is most likely due to hypoxemia and not due to increased vagal tone.  Drugs that can be used for neonate resuscitation include epinephrine, doxapram, and naloxone (only if opioids were given to the mother).  The dose for each drug is typically 1-2 drops administered under the tongue.  The neonate may also benefit from an oral dose of 2.5% dextrose if it is able to swallow a few drops.  Finally, an important aspect of neonatal care is to keep them warm by placing them in an incubator or under a heat lamp until they can be with their mother when she is fully recovered. 

Postoperative Analgesia
The postoperative pain management of the bitch is always a cause for concern due to the possibility of transfer of drugs in to the milk and therefore the neonate. Based on current research many analgesic drug classes may be safely given during the lactation period without adverse effects on the neonates (6).  Drugs that have high lipid solubility, low molecular weight, and are non-ionized are secreted more easily in to the milk.  However, it appears that only 1-2% of the maternal dose goes in to the neonate.  So opioids such as morphine or hydromorphone post-operatively would be a suitable choice for the mother. Animal studies indicate that buprenorphine has the potential to inhibit milk production. Tramadol use in lactating dogs and cats has not been specifically studied, but in humans it appears that short-term use during establishment of lactation is compatible with breastfeeding (7).  Studies have not established the safety of NSAIDs, such as carprofen, in pregnant or lactating dogs.  So it is generally recommended to avoid NSAIDs in pregnant patients and only use a single dose with caution in nursing dogs.  Clinical judgement of the attending veterinarian should prevail when it comes to selecting an analgesic drug for a patient and it should be based on assessing the patient for pain, considering the species, health status of the patient, and potential for effects on the nursing neonates.  Signs of pain in the mother could include vocalizing, not allowing to neonates to nurse, trouble moving around, and a lack of interest in food. (8)


Summary
In summary, anesthesia and cesarean section can be safely performed on dogs and cats when the anesthetist carefully selects a drug protocol, properly prepares the animal for the anesthetic episode, minimizes the anesthetic time, and provides supportive care to the neonates and mother postoperatively.

Table: Summary of Anesthesia Protocol for C-section in Dogs and Cats

Pre-medication: no drugs; (3-5 minutes of pre-oxygenation, clip and initial scrub of surgical site)
Induction: Intravenous propofol
Maintenance: isoflurane or sevoflurane
Local or regional anesthesia: lidocaine line block on proposed incision site or lidocaine epidural
Postoperative analgesia for mother: Tramadol for bitch, buprenorphene for queen

Reference List:
1. Moon PF, Erb HN, Ludders JW, et al 2000. Perioperative risk factors for puppies delivered by cesarean section in the United States and Canada. J Am Anim Hosp Assoc 36: 359-368.
2. Moon PF, Erb HN, Ludders JW, et al 1998. Perioperative management and mortality rates of dogs undergoing cesarean section in the United States and Canada. J Am Vet Med Assoc 213: 365-369.
3. Probst CW, Webb AI. 1983. Postural influence on systemic blood pressure, gas exchange, and acid/base status in the term pregnant bitch during general anesthesia. Am J Vet Res 44: 1963-1965.
4. Probst CW, Broadstone RV, Evans AT. 1987. Postural influence on systemic blood pressure in large full-term pregnant bitches during general anesthesia. Vet Surg 16: 471-473.
5. Grundy S, Liu S, Davidson A. 2009. Intracranial trauma in a dog due to being “swung” at birth. Top Companion Anim Med 23: 100-103.
6. Raffe, Marc. Veterinary Anesthesia and Analgesia: the 5th edition of Lumb & Jones. Wiley Blackwell: 2015. 34.
7. Ilett KF, Paech MJ, Page-Sharp M, et al. Use of a sparse sampling study design to assess transfer of tramadol and its O-desmethyl metabolite into transitional breast milk. Br J Clin Pharmacol. 2008 May;65(5):661-6. doi: 10.1111/j.1365-2125.2008.03117.x. Epub 2008 Feb 20.
8. Aarnes, Turi and Bednarski, Richard. Canine and Feline Anesthesia and Co-Existing Disease. Wiley Blackwell: 2015. 16.
             



Sunday, May 8, 2016

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. 


Sunday, March 13, 2016

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.



Tuesday, November 24, 2015

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.




Saturday, September 12, 2015

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.