Endocrine Organ Surgery Flashcards
Please sort these five endocrine surgeries in order from “Straightforward (if uncomplicated) and reasonable to do in general practice” at the top through to “referral surgery clinics only” at the bottom
A. Thyroidectomy in cats B. Parathyroidectomy in dogs C. Thyroidectomy in dogs D. Adrenalectomy in dogs E. Pancreatic biopsy
- Pancreatic biopsy
- Thyroidectomy in dogs
- Thyroidectomy in cats
- Parathyroidectomy in dogs
- Adrenalectomy in dogs
- Green LO* Where are the thyroid glands located?
- It’s a dark red, elongated structure attached to the outer surface of the proximal portion of the trachea.
- They are usually positioned laterally and slightly ventral to the fifth to eighth cartilage rings.
- In adult dogs they are approximately 5 cm long and 1.5 cm wide
- Green LO* Where are the PT glands located? How many are there?
- There are 4
- The external parathyroid glands are normally found on the cranial dorsolateral surface of the respective thyroid.
- The internal parathyroid glands are embedded within the thyroid parenchyma, usually at the caudomedial pole.
Green LO What is the most common cause of thyroid enlargement in dogs? What % are euthyroid/hypothyroid/hyperthyroid?
- Nonfunctional adenocarcinoma
- 60% euthyroid
- 30% hypothyroid
Green LO What is the most common cause of thyroid enlargement in cats? What % are euthyroid/hypothyroid/hyperthyroid?
- Functional adenoma or hyperplasia
- Tend to be hyperthyroid primarily
Behavior of thyroid adenocarcinomas in canines
- Nonfunctional and malignant
How to diagnose canine thyroid adenocarcinoma? What precautions must be taken?
- FNA is helpful and easy to do
- Highly hemorrhagic so plan biopsies well
In dogs, how frequently are thyroid neoplasias benign?
- ??? not sure
Prognosis for freely movable thyroid adenocarcinoma (i.e. you can feel the mass in the jugular groove)?
- 3 year median survival after surgery
Treatment for large, invasive thyroid tumors
- Radiation therapy
Green LO Answer yes or no for the following regarding thyroid masses in dogs:
- Hormone producing
- Malignant
- Bilateral
- Main surgery risks anesthesia related
- Main surgery risk hemorrhage
- No
- Yes
- Usually unilateral
- No
- Yes
Green LO Answer yes or no for the following regarding thyroid masses in cats:
- Hormone producing
- Malignant
- Bilateral
- Main surgery risks anesthesia related
- Main surgery risk hemorrhage
- Yes
- No
- Yes
- Yes
- Not as much
Green LO What complications should you always be prepared for during the surgery of thyroid neoplasia in dogs?
- Hemorrhage!
Green LO What surgical procedure is required for canine thyroid neoplasia?
- Extracapsular thyroidectomy
What do you do with the ipsilateral PTH glands in canine thyroid AC?
- Sacrifice
What happens if canine thyroid AC is bilateral?
- Dilemma
- May require calcitriol or calcium or soloxine
- This would definitely be a referral procedure
Green LO How frequently is the feline hyperthyroidism caused by bilateral disease?
- 80% bilateral
Green LO Is feline hyperthyroidism usually malignant or benign disease?
- Usually benign
- Most are adenomatous hyperplasia
Green LO Why may hypothyroidism lead to hemorrhage during surgery?
- Lots of vasculature nearby
- Carotid***
- Jugular vein
Green LO What % of cats with hyperthyroidism are affected by thyrotoxic heart disease, and how often are they in congestive heart failure?
- Thyrotoxicosis causes increased metabolic rate and sensitivity to catecholamines
- 80% of cats get cardiomyopathy
- Approximately 20% have congestive heart failure
Green LO What condition may have been masked during the hyperthyroid state and then consequently becomes a postoperative condition apparent after the cat becomes euthyroid?
- Renal disease
- GFR increase “masked” by thyrotoxocisos
Clinical signs of cats with hyperthyroidism
- Older cats
- Weight loss despite voracious appetite
- Aggression
- V/D, PU/PD
- Rough hair coat
- Palpable thyroid slip
Green LO Which are the three major approaches to treatment of feline hyperthyroidism?
- Palliative methimazole/carbimazole
- Definitive iodine 131
- Definitive surgery
Green LO How frequently is feline hyperthyroidism caused by ectopic thyroid masses?
- 5-10% of cats
Green LO Why are hyperthyroid cats considered high-risk anesthesia candidates?
- Thyrotoxicosis leads to increased metabolic rate and sensitivity to catecholamines
- 80% of cats have concurrent cardiomyopathy
- Anemia (may be occult)
- Hypovolemia
- Hypertension
- Tachydysrhythimas
- Ventricular ectopy
- Renal insufficiency that may be occult
- Increased metabolic rates
What are the palliative treatments for hyperthyroid?
- Methimazole or carbimazole
What are the definitive treatments for hyperthyroidism in cats?
- 131 iodine
- Surgical excision
Pros of methimazole
- Reversible
- Noninasive
- Maybe lower cost?
Cons of methimazole
- Daily treatment
- Reactions possible
Pros of iodine 131
- Cure >95%
- Ectopic glands
Cons of iodine 131
- Cost and hospitalization
Pros of surgery for hyperthyroidism
- Cure if benign
- Lower cost?
Cons of surgery for hyperthyroidism
- Invasive
- Anesthesia
- Complications!
Green LO How can one decrease the anesthesia risks pre-op for hyperthyroid cats?
- Methimazole for 2-3 weeks to make euthyroid
- Propanolol if methimazole not tolerated (d/c 2-3 days pre-op)
- Fluids for renal disease
Green LO Which are the 3 steps in a modified extracapsular approach for thyroidectomy?
A. Using fine-tipped bipolar cautery forceps cauterize the thyroid capsule approximately 2mm from the external parathyroid gland
B. With small, fine scissors, cut the gland at the cauterized area and remove from the parathyroid gland.
C. Carefully dissect all of the thyroid gland from the surrounding tissue and parathyroid gland.
Green LO What is the recommended action if a PTH gland becomes inadvertently excised?
- Transplant the gland to a nearby muscle belly
Green LO What are the technique options for thyroidectomy in cats?
- Modified extracapsular or intracapsular approach for thyroidectomy
Green LO Which is the most important life-threatening complication of thyroidectomy?
- Hypocalcemia risk due to the PTH gland insult (if reimplanted PTH gland can be for 1-21 days)
Green LO How long should animals be monitored for signs of hypocalcemia post-op?
- Monitor Ca often if bilateral excision
- At least daily for 5-7 days
- Every 6 hours usually and then wait to plateau then ever 12 hours
- Once you send them home, it still must be checked at the rDVM once a day for 7 days
Green LO What are the clinical signs of hypocalcemia (list 7)?
- facial twitching***
- panting
- Nervousness
- seizures
- Muscle twitching
- Ataxia
- Lethargy
- Panting
At what level of total calcium do clinical signs appear?
<7.5 mg/dL
Treatment for hypocalcemia, and what should you be monitoring?
- Acutely, give calcium gluconate IV SLOWLY (monitor HR)
- Oral calcium and vitamin D; taper after several weeks (start right away if both PTH glands were traumatized)
Other complications of thyroidectomy
- Hypothyroidism
- Recurrent hyperthyroidism
- Progression of renal disease
- Laryngeal paralysis
Green LO Which are the classical biochemical abnormalities in dogs with primary hyperparathyroidism?
- Normal to very high calcium
- Normal to low Phosphorus
- normal to high PTH for hypercalcemia
- No PTHrp
Green LO What is a sensitive test for hyperparathyroidism?
- Parathyroid panel
Green LO Thyroid panel results for renal failure
- Ca: normal to moderately high
- P: usually high***
- PTH normal to high
- PTHrp: none
Green LO Renal dysfunction may be caused by hypercalcemia or may cause hypercalcemia and elevated PTH; how can one differentiate renal dysfunction from hyperparathyroidism?
- Renal dysfunction often has high phosphorus
- Primary hyperparathyroidism can have VERY high calcium
Green LO Lymphoma or anal sac adenocarcinoma PTH panel
- High calcium
- Normal to low phosphorus
- Low PTH
- High PTHrp
Green LO D3 cholecalciferol toxicity PTH panel results
- Normal to high calcium
- Phosphorus is high
- PTH is low
- No PTHrp
Green LO Which is a more common cause of hypercalcemia than primary hyperparathyroidism?
- Paraneoplastic hypercalcemia of malignancy
- Hypercalcemia of malignancy can rapidly cause renal failure if diagnosis and therapy are delayed, but hypercalcemia caused by hyperparathyroidism is often not as high as that seen in primary hyperparathyroidism and is less likely to cause renal failure
What are two surgical options for primary hyperparathyroidism?
- Parathyroidectomy if external gland
- Partial thyroidectomy if internal gland
Green LO What is the most common postop complications after parathyroidectom yor partial thyroidectomy
- Hypocalcemia (monitor for 1-3 days)
- Also monitor renal function
Green LO What is the pathophysiological cause of hypocalcemia with parathyroidectomy?
- PTH release is what causes calcium levels to increase
- Negative feedback from high circulating levels of PTH suppress function of the other normal glands
- PTH has a functional half-life of 20 minutes and therefore PTH levels fall rapidly once neoplastic tissue has been removed
What is the major pancreatic exocrine duct in the dog?
- Accessory (minor papilla)
What is the major pancreatic duct in cats?
- Major duct (major duodenal papilla)
Blood supply to the pancreas
- Hepatic and splenic artery
- Right limb intimately associated with the supply of the duodenum
Where to biopsy a pancreatic mass?
- Can always shave a piece of the biopsy
Suture type for pancreatic mass
- Monofilament nonabsorbable
Green LO WHere is the best site for a biopsy when pancreatic disease is diffuse?
- Peripheral sites are ideal (maybe of the right limb???)
- Incision in the mesoduodenum
Green LO What are the steps when performing a small peripheral pancreatectomy by suture fracture technique?
- Incise mesoduodenum or omentum on each side of the pancreas
- Pass absorbable (3-0 to 4-0) suture material from one side to the other, through the incisions, so that the suture is just proximal to the lesion to be excised
- Tighten the suture, and allow it to crush through the parenchyma, which ligates vessels and ducts
- Excise the speciment distal to the ligature
- Close any holes in the mesoduodenum with absorbable suture material
Where do you need to be really careful excising a pancreatic mass?
- If it’s in the body of the pancreas
- Or if the ducts are nearby!
Green LO What are the steps when performing a small peripheral pancreatectomy by blunt separation of pancreatic lobules?
- Blunt separation of the lobule or lobe with Q tip or mosquito hemostat forceps
- Ligate or cauterize small pancreatic vessels but take care not to damage the pancreaticoduodenal vessels
- Using sterile Q tips or mosquito hemostats, separate the affected lobules from adjoining tissue by blunt dissection
- Identify the blood vessels and ducts supplying the portion of the pancreas to be removed and ligate them
- Excise the affected pancreatic tissue and close any holes in the mesoduodenum
Adrenal gland neoplasia - best treatments? (SKIPPED)
- SURGERY
Who should do surgery for adrenal gland neoplasia?
- Only experienced surgeons
Relative frequency of adrenal tumors
- Cortisol secreting tumors (Cushing’s) - ~40%
- Pheochromocytomas
- Metastasis (27% dogs; 60% cats)
- Sex hormone production (Atypical cushing’s)
- Conn’s (hyperaldosteronism) in cats
- Non-functional neoplasia
