Ch 121 thyroid and parathyroid Flashcards

Question

clinical signs of hypoCa

Answer 1

- restlessness, facial or generalized muscle twitching, weakness, anorexia, panting, tetany, or convulsions - may occur 12 hours to 6 days postoperatively - Only 60% of cats with severe hypocalcemia (total calcium <6.5 mg/dL or ionized calcium <0.8 mmol/L) demonstrate clinical signs

Answer 2

0.5-1.5ml/kg 10% Ca gluconate slowly IV, with ECG monitoring Followed by CRI of Ca gluconate at 5-15mg/kg/hr IV Alternatively 10ml 10% Ca gluconate added to 250ml bag and administered at 60ml/kg over 24hr - Do not add Ca to LRS as it precipitates - Do not used Ca carbonate IV or SQ

Answer 3

* Oral Vit D (calcitriol) and calcium * up to 3 months. Monitored weekly and tapered as required With autotransplantation, hypocalcemia usually resolves within 21 days; without, can last up to 3 months goal is to maintain the serum calcium concentration in the low-normal range (8.5 to 9.5 mg/dL). This prevents clinical signs of hypocalcemia while still stimulating growth and function

Answer 4

* Rare so relatively unknown * Marginal thyroidectomy + I131 - survival 10-41m * High dose I131 alone - 6/8 euthyroid with survival time 181-2381d

Answer 5

* Methimazole or carbimazole * Iodine-restricted diets (y/d) - 75-90% become euthyroid * Radioactive iodine (I131) - Tx of choice. Single dose results in cure in most and ectopic tissue is also treated (considered carefully in regard to renal function)

Answer 6

* 90% thyroid carcinomas * 25-47% bilateral * Up to 40% mets a diagnosis, 80% develop mets * 10-29% hyperthyroid

Answer 7

- in necropsy studies, 30% to 50% of thyroid tumors are benign adenomas - 90% of thyroid tumors detected clinically are malignant - large; poorly encapsulated; and extend locally into or around the trachea, esophagus, and muscles of the neck - highly vascular and invade local blood vessels. - Approximately 25% to 47% of thyroid carcinomas are bilateral - 13% are ectopic thyroid tissue at the base of the tongue, ventral neck, cranial mediastinum, or heart base - two distinct groups of thyroid tumours are recognised, based on degree of mobility and local invasiveness - Thyroid carcinomas appear to be poorly to moderately sensitive to chemotherapeutic agents classified - papillary, follicular, compact, or anaplastic - most common: follicular and compact mets - 40% detectable metastatic disease at presentation - 80% develop metastasis during the course of the disease - lungs and regional lymph nodes (retropharyngeal lymph nodes the most common sites) - viscera, brain, spinal cord, and skeleton functional - 10% to 29% are hyperthyroid - 60% are euthyroid - commonly interpreted as functional if there is clinical and/or laboratory evidence of hyperthyroidism. Most canine thyroid carcinomas are not in fact hypersecretory - most have follicular elements and are capable of trapping and organifying radioiodine. - human medicine the term ‘functional’, when applied to thyroid tumours, refers to the ability of the neoplastic tissue to trap and organify radioiodine - Judging the ‘functional’ ability of a tumour and whether radioiodide therapy is a rational option for treatment based only on hypersecretion of thyroid hormones is inappropriate (worth 2005) - Tumour ‘functionality’ can only be accurately assessed with thyroid scintigraphy

Answer 8

Golden Retrievers, Beagles, and Siberian Huskies

Answer 9

- palpable mass, dyspnea, dysphagia, change in bark, and facial edema - Palpation is not very accurate to determine local invasion - ultrasonography, CT, and MR cannot be absolutely definitive regarding mass resectability > sx exploration more definitive Ultrasonography - determination of the origin of the mass - whether the condition is bilateral - information regarding invasiveness and, by use of pulsed or color-flow Doppler, vascularity. CT - determine origin, invasiveness, and vascularity of the mass and the presence of metastasis - highly specific for determining histopathologic invasion of thyroid tumors (100%) but MRI is more sensitive for this purpose (93%) Cytology and Biopsy - usually adequate to confirm that the mass is of thyroid origin - cyto not a reliable means to distinguish between benign and malignant - Tru-Cut is not recommended because of the high risk of severe, and sometimes fatal, hemorrhage

Answer 10

Inhibitory effect on thyroid uptake of radioiodine and pertechnetate

Answer 11

Total T4 Free T4 TSH

Answer 12

- pertechnetate ion is trapped by the thyroidal iodide-concentrating mechanism, highlighting glandular tissue - scintigraphy can be used to determine if a mass is of thyroid origin. - poorly circumscribed on scintigraphy are more likely to be invasive. - also helpful for identifying ectopic tissue - Scintigraphy has been suggested as a means to determine the likelihood of response to I131 treatment, this is only true, however, when using a tracer that is incorporated into organic thyroid hormone

Answer 13

- minimum database - staged with three-view chest radiographs and abdominal ultrasonography/CT to assess l.n. - cross-match for blood transfusion - dogs with hyperthyroidism do not need treatment to induce euthyroidism

Answer 14

- freely movable defined as ≥1 cm in all planes during palpation - Large or invasive tumors tend to be excessively well vascularized and can potentially invade or incorporate the jugular vein or carotid artery, requiring ligation of these vessels. - Bilateral carotid artery ligation can be performed in dogs because of extensive collateral development but when performed acutely, it may result in intraoperative tachycardia and hypertension - cautery, hemoclips, ligasure, harmonic scaler - thyroidectomies in dogs are performed with a marginal excision, and a complete excision is often achieved - The ability to attain an adequate margin of normal tissue depends on the structures - structures within the carotid sheath, and laryngeal recurrent nerve > possible to sacrifice these unilaterally with acceptable morbidity because unilateral Horner's syndrome and laryngeal paralysis usually do not affect quality of life. - unilateral vagus sacrifice usually no problem - Bilateral cervical vagotomy leads to high morbidity and mortality in dogs - Marginal excision of thyroid tumors can lead to excellent local tumor control; therefore, dissection of critical structures off the tumor, rather than transection or resection of them, is recommended.

Answer 15

- bilateral fixed lesions because of high postoperative morbidity, including laryngeal paralysis, megaesophagus, and aspiration pneumonia from damage to nearby nerves - tumor invades the esophagus or trachea fixed vs mobile removal of more invsive tumors is associated with higher morbidity and mortality > especially bilaterally invasive, poorer outcome. Tuohy 2012 roeprted good outcome with no mortiality or recurrence for bilateral, mobile tumors fixed may invade oesophagus, trachea, muscles and increase vascularisation. morbidity = megaoesophagus, laryngeal paralysis +- aspiration, haemorrhage with increase requirement of transfusion. excellent results reported for marginal excision > more likeley achieved with mobile/less invsaive 3yr survival for mobile, 6-12mths for fixed

Answer 16

Indocyanine green near-infrared fluorescent imaging

Answer 17

- freely movable tumors tend to remain within the natural capsule - When the tumor is unilateral, no attempt should be made to preserve these glands because of the greater risk of leaving tumor cells and ypoclacemia not concern - With bilateral disease > prepared to treat the dog for postoperative hypoparathyroidism - if a parathyroid gland can be identified and preserved, this should and can be done post-op - If significant nerve damage occurred during the surgery or if bilateral thyroidectomy was performed, the dogs are monitored for laryngeal paralysis and other complications

Answer 18

At least daily for 3-7 days with Ca and Vit D supplementation

Answer 19

Surgical excison (freely movable most amenable) Radiation therapy Radioactive I131

Answer 20

* Haemorrhage and anaemia * Hypothyroidism (40% if bilateral) * Laryngeal paralysis * Megaoesophagus (bilateral vagus) * Hypoparathyroidism and hypocalcaemia (21/27 dogs with bilateral thyroparathyroidectomy). Many require lifelong therapy

Answer 21

* Mobility (resectability/margins) * Size * Stage of disease * Vascular invasion * benign (adenoma, sx can be cure) Overall MST 22m | Even with incomplete margins, the prognosis can be excellent.

Answer 22

* Diameter * Volume * Fixation * Ectopic location * Follicular cell origin MST 3yr if freely movable vs 6-12m if more invasive

Answer 23

Bilateral disease and tumour size - 14% if less than 23cm^3 - 100% over 100cm^3 Bilateral tumours are 16x more likely to met

Answer 24

13% ectopic tumour - Sublingual (may require partial hyoidectomy) - Cranial mediastinal Tx with surgical excision, I131 or external beam radiation therapy

Answer 25

- nonresectable or incompletely resected thyroid - Thyroid tumors do not need to be functional to respond to I131 treatment - radionuclide scan aid in the determination of the likelihood of response > tumors that do not adequately concentrate the radioisotope are less likely to respond to therapy - MST without metastatic disease was 839 days - MST with metastasis 366 days - Three dogs (8%) died of I131-induced myelosuppression *medullary thyroid carcinomas = C-cell tumours – do not take up iodide or produce T4*

Answer 26

- invasive or incompletely resected tumors - nonresectable tumors (48 Gy (4 Gy/fraction) had a mean progression-free survival of 45 months and 3-year progression-free survival rate of 72% - 96 weeks for dogs with pulmonary metastases and 127 weeks for those without

Answer 27

- role of adjuvant chemotherapy poorly defined. - doxorubicin or cisplatin, 30% to 50% demonstrated a partial response

Answer 28

- Tumors in the cranial mediastinum: surgically excised, I131 or radiation therapy. - tumors that involve the heart are typically intracardiac and therefore challenging to surgically excise - tumors in the sublingual area can be amenable to surgical excision - The hyoid apparatus is often involved > basihyoid bone appears to be the one most common - MST surgery (873 days) was significantly longer than not receive surgical treatment (481 days) - results may reflect size of the mass, the presence of metastatic disease, or tumor type.

Answer 29

- excision of the basihyoid bone and variable portions of the thyrohyoid, epihyoid, and ceratohyoid bones would be expected to have negative consequences on laryngeal and pharyngeal function - Placement of hyoid apparatus–stabilizing sutures is an attempt to ameliorate - Dogs tolerate partial hyoidectomy very well. - no signs of dysphagia, ptyalism, or abnormal tongue carriage

Answer 30

Cardiovascular - Decreased contractility - Increased vascular resistance - Decreased vascular volume - Artherosclerosis Suppression of humoral immune response, impariment of T-cell function and reduction in number of circulating lymphocytes Effect on wound healing varies by species but may disturb fibroblast deposition of collagen, keratinocyte proliferation | euthyroid sick syndrome, TSH is usually within the normal

Answer 31

Primary - Excessive production and secretion of PTH by abnormal, autonomously functioning parathyroid chief cells. Keeshond predisposed. Maybe also Siamese Secondary: - Renal secondary hyperparathyroidism - Nutritional secondary hyperparathyroidism - imbalances in phosphorus, Vit D or Ca

Answer 32

- Most nodules in dogs are adenomas or adenomatous hyperplasia; - up to 5% are carcinomas - 90% of dogs and cats have 1 nodule - 42% of dogs had 2 abnormal glands - RARE > all 4 glands hyperplastic, secondary hyperparathyroidism suspected. - Metastasis rare - Ectopic parathyroid adenocarcinoma has also been reported in the cranial mediastinum

Answer 33

Skeletal effects - PTH-induced resorption of Ca2+ from bone - Fibrous osteodystrophy (skull) - Pathologic fractures Renal effects: - Renal tubular mechanisms become overwhelmed and excessive Ca excretion results (despite high PTH) - Urolithiasis, UTI, PU/PD, diabetes insipidus - Hypercalcemia can decrease renal function by two means - If Ca x P product is greater that 60-80 mg/dL, soft tissues calcify, causing renal dysfunction - Renal vasoconstriction and decreases renal blood flow. - production of vitamin D also increases, exacerbating hypercalcemia. About 4% of dogs with primary hyperparathyroidism will have renal damage

Answer 34

HARDIONS Hyperparathyroidism (primary and secondary) Addison’s (hypoadrenocorticism) Renal failure (acute and chronic) Vitamin D toxicity Idiopathic (cats) or infection (granulomatous disease, eg. fungal disease) Osteolysis (rare; reported with osteomyelitis and hypertrophic osteodystrophy) Neoplasia (lymphoma, MM, anal-sac adenocarcinoma) Spurious (lab error, excessive supplementation, etc.)

Answer 35

- nodules can be palpated in 50% of affected cat - normal ionised Ca: 1.1mmol/l - 1.4mmol/l - ideally check PTH, and PTH–related peptide (PTH-rp) concentrations ultrasound - normal are hypo-anechoic - parathyroid nodules as small as 0.5 cm in diameter can be detected - very accurate, but negative ultrasound results do not rule out a tumor scintigraphy - double-phase parathyroid scintigraphy had poor sensitivity and specificity > not recommended

Answer 36

Inappropriate PTH (normal or high) on the face of increased ionised Ca. Low PTH-rp - Differes from CKD (renal secondary hyperparathyroidism) as primary hyperparathyroidism will have decreased phosphate (as apposed to elevated) and are not azotaemic. - Patients with increased PTH-rp should undergo further diagnostics for neoplasia - PTH-rp may also be elevated in dogs with CKD without malignancy - hypercalcemic and have [PTH] within the reference range are still considered to have excessive PTH

Answer 37

Medicam management if concurrent renal failure or Ca-phosphorus ratio greater than 60-70 - Saline diuresis 120-180ml/kg/d - Furosemide - K supplementation PRN - If above fails, glucocorticoids can promote calciuresis - If all above fails, bisphosphonates or calcitonin

Answer 38

External: - Parathyroidectomy - Partial thryoidectomy (guillotine technique, ensure preserve blood supply to rest of thyroid) Internal: - Partial thyroidectomy (ipsilateral external parathyroid gland should be preserved) - If carcinoma, complete thryoparathyroidectomy | cystotomy to remove the calculi can be done under the same anesthesia

Answer 39

Intra-op measurement of PTH with rapid chemiluminescent assay - Decrease by less than 50% baseline after 10 mins indicates autonomously function tissue remaining - not alwyas accurate IV methylene blue - Dose required has too high a risk of toxicity (Heinz body anaemia and acute renal failure) - NOT recommended Indocyanine green near-infrared imaging - promising experimentally some delay Sx if the affected parathyroid gland cannot be identified preop by an experienced ultrasonographer (repeat u/s until larger) ectopic anatomic location

Answer 40

Three of four parathyroid glands can be safely removed without a risk of permanent hypoparathyroidism

Answer 41

Fluids & Analgesia Calcium Monitoring: - Serum total or ionized calcium checked 1-2 x daily for 5-7 days. - Preoperative calcium levels may or may not predict postoperative hypocalcemia. Calcitriol Therapy: - Some protocols start calcitriol only if preoperative calcium is high (>1.75 mmol/L). - Others recommend starting calcitriol for all dogs - Tx can last up to 2 months, requiring frequent monitoring. Weaning Off Calcitriol: - Initial doses: 20-30 ng/kg in the morning and 10-15 ng/kg in the evening of surgery. - Gradual reduction by 10% every 4 days over 45-60 days while monitoring calcium levels. - Adjustments needed if (Ca <0.95 mmol/L ionized) or too high. Exercise Restriction: - Dogs: At least 6 days to prevent tetany from hypocalcemia. - Cats: Kept indoors for 14 days.

Answer 42

HypoCa - 35-70%, - 25% of which develop clinical signs between 12hr-20d (most commonly within 1 week) - all four parathyroid removed > life long Tx (only 3% to 6% of dogs have accessory parathyroid tissue) - tx if CS or <0.95mmol/L - acute Tx: 0.5 to 1.5 mL/kg slowly to effect, monitored by ECG for bradycardia and arrhythmias - maintenance: 10 mL of 10% calcium gluconate in a 250-mL bag of 0.9% sodium chloride solution and administer it at 60 mL/kg/day IV - long-term: Calcitriol is the vitamin D 0.005 to 0.015 µg/kg/d divided twice daily, oral elemental calcium is 25 to 50 mg/kg/d divided into 2 to 3 daily doses Recurrence - 8% within months to years. - Second surgery usually highly successful - dt multiglandular disease, ectopic glands, incomplete removal or metastasis Overall prognosis is excellent, even with parathyroid carcinoma (Hyper Ca resolved in 44/47 with median follow up of 561d)

Answer 43

* Ultrasound guided ethanol ablation * Ultrasound-guided heat ablation Inconsistent results

Answer 44

41 cats thyroidectomy (n = 15) and methimazole (26) survival time was significantly longer with thyroidectomy (1893d) than with methimazole (730d) The recurrence rate was significantly lower in cats that underwent thyroidectomy

Answer 45

Alendronate overall was well tolerated with chronic use in this cohort, and can be considered a treatment option for persistent ionized hypercalcemia in cats use of glucocorticoids (or furosemide) usually is reserved for short-term treatment of severe symptomatic Bisphosphonates inhibit osteoclastic activity by altering intracellular protein trafficking and perturbing normal cytoskeleton physiology,16 which results in decreased bone resorption and decreased calcium release

Answer 46

Animals: Fifty client-owned dogs with PHPT that underwent minimally invasive parathyroidectomy. Study design: Retrospective cohort study ultrasound-guided mini lateral approach. Abnormal parathyroid glands were removed en bloc via partial thyroidectomy. 17 hyperplastic glands (17/62, 27.4%), 34 adenomas (34/62, 54.8%), and two carcinomas(2/62, 3.2%). Hypercalcemia resolved shortly after surgery in 44 dogs (97.8%). One dog had recurrent hypercalcemia (1/45, 2.2%), one dog had persistent hypercalcemia (1/45, 2.2%), two dogs had permanent hypocalcemia and one dog died from clinical hypocalcemia (1/45, 2.2%). hungry bone syndrome (HBS).33 HBS is encountered in humans that have a high preoperative bone turnover rate star retractor and bipolar

Answer 47

Agreement of ultrasonography and surgery on parathyroid pathology, and predictors of postop hypocalcemia in 47 dogs * u/s and surgery agreement: number of affected glands 31/47 (65.9%) affected side 34/47 (72.3%) * u/s cut-off ≥8.0mm → distinguished malignant from benign * surgical exploration of both sides recommended – * surgeons were found to be more successful at identifying parathyroid pathology > but 23.4% normal tissue excised * pre-op iCa ≥1.75mEq/L → 7.5x greater odds of post-op hypocalcemia * 47% subclinically hypocalcemic, 17% clinically hypocalcemic post-op inconsistency in identifying parathyroid pathology on ultrasound > inferior cure rates of ultrasound guided ablation compared with surgical excision (70% versus 95%) ultrasonography > only a moderately reliable tool

Answer 48

To determine the rate of nodal metastasis to the medial retropharyngeal (MRP) and deep cervical lymph nodes in dogs surgically treated for thyroid carcinoma. Study design: Retrospective study. Animals: Twenty-two client-owned dogs Metastases were identified in 14 lymph nodes in 10 of 22 (45%) dogs. All four excised deep cervical lymph nodes and one contralateral MRP lymph node were identified as metastatic Regional metastasis was common within the lymph nodes sampled in this population of dogs with thyroid carcinoma.

Answer 49

Retrospective cohort study. ANIMALS 42 client-owned dogs Hemostatic technique (ie, use of a VSD vs conventional hemostatic techniques) was the only factor significantly associated with operative duration (median time, 28 vs 41 minutes). Postoperative hospitalization times and complication rates did not differ between groups. VSD, rather than conventional hemostatic techniques, in dogs undergoing thyroidectomy because of suspected thyroid carcinoma resulted in shorter operative times without significantly affecting complication rates or postoperative hospitalization times Major complications were reported in 3 dogs in which conventional hemostatic techniques were used. One dog developed acute bleeding from the surgical incision 3 hours after the procedure Four dogs in which a VSD was used had major complications. One dog had iatrogenic esophageal perforation when the esophagus was inadvertently included in the jaws of the VSD. Two dogs developed aspiration pneumonia

Answer 50

Unilateral thyroidectomy in 156 dogs with thyroid tumors: retrospective complications (19.9%) hemorrhage > most common [7.7%] Five (3.2%) received blood transfusion aspiration pneumonia (5 [3.2%] dogs) > 2 revealed bilateral laryngeal paralysis. perioperative mortality rate of 3.4% (98.1%) survived to discharge most lost to follow up > MST 911 days Post-op metastatic disease or local recurrence in 22 dogs. gross vascular invasion (34.6%) and lymph node metastasis (7.1%) capsular invasion [61.5%] dogs Factors associated with complication rate> whether the mass was assessed as fixed or mobile during physical examination. 5.4 times the odds for dogs with a mobile mass Only (11.5%) tumors considered fixed > treatment bias shorter progression-free interval > mitotic index and tumor size

Answer 51

27 dogs. Outcomes functional (hyperthyroidism) thyroid tumors treated by surgical excision alone [85%] malignant. Estimated MST 1,072 days. No significant prognostic factors were identified. 1 x metastatic disease @ diagnosis (4%) > survival 87d recurrence > 1 dog (48%) required lifelong supplemental thyroid hormone resectable functional thyroid tumors > good prognosis with surgical excision alone (may be picked up earlier dt clinical signs)

Answer 52

functional thyroid tumours in 70 dogs Sx > MST 72.6 months vs no Sx >15.7 months (radiation, chemotherapy, methimazole) 54% showed Clinical signs. 16% bilateral. 18% ectopic 23% described as fixed 64% developed hypothyroidism after surgery. Peri-operative complications > 4 deaths (5%) Dogs with functional thyroid tumours may survive a long time after surgical excision, although post-operative hypothyroidism is common neoplastic tissue primary contributor to hyperthyroidism

Answer 53

– review of thyroid carcinomas - follicular thyroid carcinoma (FTC) or medullary thyroid carcinoma - MCT prevalence 5-36% - FTC → follicular, mixed, compact and papillary subtypes - biologic behaviour: - metastasis: regional LN 14-26%; distant 20-38%; overall 18-95% - FTC → lung - MTC → cervical LN * treatment: I131 uptake related to degree of differentiation> MTC may not take up I131 but effect may be from adjacent follicular cell uptake - prognosis: good-excellent; MST: sx alone 7-36+ months; untreated 3 months

Answer 54

- fixed tumours → 5.4x increased risk of complication - metastasis: LN: 7.1-45% - prognosis: - negative indicators: fixed tumour – MST 6-12m vs 3y large tumour dimensions → shorter DFI/no effect on survival → higher rate of metastasis vascular invasion, Ki-67, mitotic index (DFI and ST) higher WHO stage - positive indicator: surgical excision - not associated: tumour functionality

Answer 55

- cadaveric feasibility and 5 clinical cases - 1.5cm midline incision, 1 finger-width caudal to cricoid → 5mm 30° endoscope - parathyroidectomy with electrocautery and blunt/sharp dissection - use of blunt suction-dissector facilitated dissection

Answer 56

pre-op iCa median 1.8mmolL – above ref range in all cats; not correlated to post-op iCa - pathology: 20/32 (62.5%) parathyroid adenoma, 7/32 (21.9%) PT carcinoma - post-op complications: 2/32 laryngeal paralysis - post-op hypercalcemia 6/32 (18.8%) - MST overall 1109 d - not associated with pre-op iCa, hypo/hypercalcemia at discharge, carcinoma dx

Answer 57

parathyroid carcinomas in dogs: 100 cases 96% clinical/incidental hypercalcemia - cervical ultrasound: 91/91 detected, (70.3%) single, (25.3%) 2 nodules (4%) ≥3 nodules - hypercalcemia resolution: 92% within 7 days - hypocalcemia: (34%) within 7 days → 3 euthanasia refractory hypoCa - 1 metastasis to prescap LN - survival: MST 735d; estimated 1y 84%, 2y 65%, 3y 51%

Ch 121 thyroid and parathyroid Flashcards

(86 cards)