Double-phase parathyroid scintigraphy in dogs using technetium-99M-sestamibi

Surgical description and outcome of ultrasound-guided minimally invasive parathyroidectomy in 50 dogs with primary hyperparathyroidism

OBJECTIVE

To describe the surgical technique and clinical outcome of minimally invasive parathyroidectomy for primary hyperparathyroidism (PHPT) in the dog.

ANIMALS

Fifty client-owned dogs with PHPT that underwent minimally invasive parathyroidectomy.

STUDY DESIGN

Retrospective cohort study.

METHODS

An ultrasound-guided mini lateral approach was made via a plane established between the sternocephalicus muscle and sternohyoideus muscles to expose the thyroid gland and enlarged parathyroid gland. Abnormal parathyroid glands were removed en bloc via partial thyroidectomy. The technique for bilateral disease was similar, the skin incision was made on midline and moved laterally to develop the above-mentioned plane of dissection. Age, sex, breed, bodyweight, ultrasound findings, histopathological diagnosis, surgical time, preoperative clinical signs, and clinical outcome were extracted from the records for descriptive statistics.

RESULTS

A total of 62 glands were surgically removed, including 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 (44/45, 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 requiring life-long calcitriol supplementation (2/45, 4.4%), and one dog died from clinical hypocalcemia (1/45, 2.2%).

CONCLUSION

Minimally invasive parathyroidectomy was associated with a low morbidity and led to favorable outcomes in 44/45 dogs in this series.

CLINICAL SIGNIFICANCE

The results of this study supports the use of minimally invasive parathyroidectomy to treat PHPT in dogs.

99m-Technetium-Pertechnetat- und 99m-Technetium-Sestamibi-Szintigrafie zur Darstellung von hypofunktionellem Schilddrüsengewebe und Staging bei einem Hund mit Schilddrüsenkarzinom

Eine 10-jährige Mischlingshündin wurde aufgrund einer zervikalen Umfangsvermehrung zur Schilddrüsen-Szintigrafie vorgestellt.

Aufgrund einer zusätzlichen Hypothyreose, die einen „kalten“ Knoten vermuten ließ, und zur Metastasensuche, erfolgte neben der 99m-Technetium-Pertechnetat (Tc-Pertechnetat)-Szintigrafie eine zweite Szintigrafie mit 99m-Technetium-Sestamibi (Tc-MIBI).

Zwanzig Minuten nach intravenöser Gabe von 38 MBq Tc-Pertechnetat waren ein „heißer“ zervikaler und ein intrathorakaler Knoten mit einem „Uptake“ von 8,40 und 0,25 % sichtbar. In der zweiten Szintigrafie 20 Minuten nach intravenöser Gabe von 364 MBq Tc-MIBI und 70 Minuten nach der ersten Szintigrafie zeigten die Knoten nach Abzug der Pertechnetat-Aktivität und Zerfallskorrektur einen „Uptake“ von 0,99 und 0,03 %. Zudem stellten sich in der Schilddrüsenloge beide Schilddrüsenlappen mit einer geringen Tc-MIBI-Aufnahme dar. Das Verhältnis Tc-„Uptake“/Tc-MIBI-„Uptake“ betrug für beide Läsionen 8,48 bzw. 8,33.

Nach Exstirpation des zervikalen Tumors ergab die histopathologische Untersuchung atrophisches Schilddrüsengewebe, das von einem expansiv wachsenden gut differenzierten follikulären Schilddrüsenkarzinom fast vollständig verdrängt wurde.

Dieser Fallbericht beschreibt Durchführung, Nutzen und rechnerische Korrektur einer aufeinanderfolgenden Pertechnetat- und MIBI-Szintigrafie, die eine Darstellung von hypofunktionellem Schilddrüsengewebe ermöglichte. Die beiden heißen Knoten waren daher und aufgrund ihrer gleichen MIBI-Stoffwechselaktivität als dystopes Gewebe/Metastasen zu werten, wodurch die Hündin in das prognostisch ungünstigere WHO-Stadium IV klassifiziert werden musste. Anders als beim Menschen sollten beim Hund zur Vermeidung einer erneuten Narkose beide Szintigrafien kurz hintereinander durchgeführt werden. Eine qualitative/visuelle Beurteilung des MIBI-Szintigramms ist daher nicht sicher möglich, sodass eine quantitative Beurteilung über den „Uptake“ nach rechnerischer Korrektur der Pertechnetat-Aktivität erfolgen muss.

Ambidirectional cohort study on the agreement of ultrasonography and surgery in the identification of parathyroid pathology, and predictors of postoperative hypocalcemia in 47 dogs undergoing parathyroidectomy due to primary hyperparathyroidism

Objective

To investigate (1a) agreement of ultrasonographic, surgical, and histopathologic findings in the diagnosis of a neoplastic etiology underlying primary hyperparathyroidism (PHPT), (1b) the ability of ultrasonographically determined parathyroid gland size to distinguish between malignant (carcinoma) and non‐malignant (hyperplasia, adenoma) pathology, and (2) variables associated with postoperative hypocalcemia in dogs undergoing surgical treatment of PHPT.

Study Design

Ambidirectional cohort study.

Animals

Forty‐seven client owned dogs with PHPT (34 retrospective; 13 prospective).

Methods

Data were extracted from medical records. Method agreements were explored using Cohen's Kappa statistic. A receiver operating characteristic curve (ROC) was used to determine a cut‐off separating parathyroid pathologies. Univariable and multivariable models assessed associations between postoperative hypocalcemia and potential risk factors.

Results

Agreement of ultrasound and surgery for number and side of affected glands was 31/47 (65.9%) and 34/47 (72.3%), respectively. In 37/47 (78.7%) cases, parathyroid tissue was correctly assessed as pathologic by the surgeon. An ultrasonographic cut‐off of ≥8.0 mm (ROC AUC = 0.82) best distinguished malignant from benign pathologies. Dogs with a preoperative serum ionized calcium (iCa) concentration ≥1.75 mEq/L had 7.5 times greater odds of becoming hypocalcemic postoperatively.

Conclusion

A fair agreement existed between ultrasonographic and surgical findings in dogs with PHPT. A parathyroid mass ≥8.0 mm on ultrasonographic examination was suggestive of malignancy, while dogs with a preoperative serum iCa concentration ≥1.75 mEq/L were at increased risk for postoperative hypocalcemia in this study.

Clinical significance

This study supports the use of bilateral cervical surgical exploration to identify abnormal parathyroid glands for the treatment of PHPT.

CT imaging features of the normal parathyroid gland in the dog

OBJECTIVE

Aim of our prospective pilot study was to assess the feasibility of computed tomography (CT) to visualize the normal parathyroid gland in dogs and provide a description of its CT appearance.

MATERIAL AND METHODS

A total of 25 dogs, which received CT imaging including the neck region for diseases unrelated to the thyroid or parathyroid glands, were enrolled. Inclusion criteria were a normal physical examination, an unremarkable complete blood count and serum chemistry profile. Pre and post contrast CT images were acquired using a 16-slice helical scanner with an 18 cm field of view, 1 mm slice thickness and a 512 × 512 matrix. Post contrast images were obtained 30-45 seconds following contrast medium injection (early venous phase). CT-images were independently reviewed by 2 radiologists. Visibility of the parathyroid gland was recorded and inter-observer agreement was calculated. For all visualized parathyroid glands the following parameters were assessed: size, density in Hounsfield units (HU) on pre and post contrast images, density of the thyroid gland and border definition (excellent, moderate, poor).

RESULTS

Only 20 respectively 25 parathyroid glands could be visualized by the 2 observers. The number did not vary between pre and post contrast images. The inter-observer agreement for the identification was fair (κ = 0.40). Length, width and height (mean ± standard deviation) of the parathyroid gland were 4.2 × 2.5 × 2.9 mm ± 1.3 × 0.8 × 1.0 mm. The density was 39.7 ± 20.6 HU on pre contrast images and 103.1 ± 47.1 HU on post contrast images, thus the organ was hypoattenuating compared to the thyroid gland on pre (166.7 ± 34.3 HU) and post contrast (234.0 ± 60.1 HU) images.

CONCLUSION

This study offers the first description of the CT appearance of the presumed normal canine parathyroid gland. However, the overall visibility was poor.

CLINICAL RELEVANCE

Despite the overall poor visibility of the parathyroid gland it was occasionally visible and its CT dimensions were larger as described for ultrasound in this group of dogs, which showed no clinical signs of hyperparathyroidism. Thus, visibility of the parathyroid gland on CT may not necessarily imply parathyroid disease. However, further research is necessary.

Association of Hypercalcemia Before Treatment With Hypocalcemia After Treatment in Dogs With Primary Hyperparathyroidism

BACKGROUND

Development of hypocalcemia after treatment of hyperparathyroidism results in increased costs and risk of poorer outcomes. Previous studies have shown conflicting data about predictors of hypocalcemia after these procedures.

HYPOTHESIS/OBJECTIVES

The objective of this study was to investigate whether ionized calcium (iCa) concentrations before treatment are predictive of hypocalcemia or its clinical signs after surgical removal or heat ablation in dogs with primary hyperparathyroidism.

ANIMALS

Fifty-four dogs with primary hyperparathyroidism (29 female, 25 male; 49 retrospective, 5 prospective).

METHODS

Dogs were enrolled if they met the inclusion criteria: persistent hypercalcemia (iCa >1.41 mmol/L) due to primary hyperparathyroidism and absence of preemptive calcitriol treatment. All dogs were treated with parathyroidectomy (n = 37) or percutaneous ultrasound-guided heat ablation (n = 17). After treatment, iCa was monitored twice daily until plateau or intervention.

RESULTS

There was a moderate correlation between before-treatment hypercalcemia and after-treatment hypocalcemia. The prospective study was terminated due to ethical concerns given findings in the retrospective section. All dogs were placed into groups according to their pretreatment iCa: 1.46-1.61 mmol/L, 1.62-1.71 mmol/L, iCa 1.72-1.81 mmol/L, or >1.81 mmol/L. After treatment, the mean lowest iCa for each group, respectively, was 1.19, 1.18, 1.13, and 1.01 mmol/L. There was a significant association between higher group and proportion of dogs with iCa <1.00 mmol/L (P = .014).

CONCLUSIONS AND CLINICAL IMPORTANCE

This study demonstrates a moderate correlation between iCa concentration before treatment and hypocalcemia after treatment. Dogs with higher initial iCa concentrations should be treated to prevent rapid decline and development of clinical hypocalcemia.

Disorders of the parathyroid glands

The three calcitropic hormones, parathyroid hormone (PTH), 1,25-dihydroxycholecalciferol and calcitonin are together responsible for calcium homeostasis in the mammal. Feline PTH is an 84 amino acid, single chain polypeptide with a molecular weight of 9449, which is secreted by the parathyroid glands. The principle secretagogue for PTH is a low plasma ionised calcium concentration, although both 1,25-dihydroxycholecalciferol and phosphate have significant roles in regulating PTH secretion. The ability to accurately measure circulating PTH in the cat has simplified the evaluation of disorders of calcium metabolism in this species. In primary parathyroid disorders the lesion is located within the parathyroid gland, with parathyroid secretion being inappropriate to the prevailing mineral balance. By contrast, in secondary conditions a pathological state out with the parathyroid gland alters mineral homeostasis and the parathyroid gland responds in an appropriate manner. The measurement of circulating PTH may then be used to determine if PTH secretion is appropriate to the prevailing calcium concentrations to differentiate primary from secondary disorders. Although primary hyper and hypoparathyroidism are generally considered rare endocrine conditions of the cat, the ability to measure PTH has led to their increasing recognition.

Intraoperative parathyroid hormone concentration to confirm removal of hypersecretory parathyroid tissue and time to postoperative normocalcaemia in nine dogs with primary hyperparathyroidism

OBJECTIVE

To determine (1) whether the intraoperative parathyroid hormone concentration ([PTH]) during parathyroidectomy (PTX) can be used to indicate cure in dogs with primary hyperparathyroidism and (2) the time taken for postoperative serum calcium concentration to normalise.

DESIGN

Retrospective study (2005-10) from a private referral hospital in Sydney, New South Wales, Australia.

PROCEDURE

Nine client-owned dogs underwent surgical PTX for naturally occurring primary hyperparathyroidism. [PTH] was measured from serum samples taken immediately post-induction (pre-PTX]) and at least 20 min after adenoma removal (post-PTX) for all dogs, and during parathyroid gland manipulation (intra-PTX) for six dogs. The concentration of ionised calcium (iCa) was measured at various time points postoperatively until it normalised, then stabilised or decreased below reference ranges. Statistical analysis compared the mean pre-, intra- and post-PTX [PTH] and the average rate of decline of iCa concentration postoperatively.

RESULTS

All dogs demonstrated a significant decrease from mean pre-PTX [PTH] (168.51 pg/mL) to mean post-PTX [PTH] (29.20 pg/mL). There was a significant increase in mean intra-PTX [PTH] (279.78 pg/mL). The average rate of decline of iCa concentration postoperatively to within the reference range (1.12-1.40 mmol/L) occurred after 24 h.

CONCLUSION

Intraoperative measurements of [PTH] can be used clinically to determine cure of primary hyperparathyroidism. Parathyroid hormone increases significantly during parathyroid gland manipulation. Plasma iCa concentration returns to within the reference range on average 24 h after successful PTX. Not all dogs require vitamin D or calcium supplementation pre- or postoperatively.

Metabolic complications of endocrine surgery in companion animals

Metabolic complications of endocrine surgery occur commonly and precautions should be taken to avoid potentially life-threatening situations and to lessen expense associated with a more extended hospital stay. Common complications of endocrine surgery as well as prevention strategies will be reviewed for pancreatic, parathyroid, and adrenal surgery.

Diagnosing the etiology of hypercalcemia in a dog: a case of primary hyperparathyroidism

A 13-year-old spayed Labrador Retriever cross dog presented for polyuria and polydipsia. Serum total calcium, free calcium, and intact parathyroid hormone concentrations were elevated. Surgical exploration of the ventral neck revealed a grossly enlarged right external parathyroid gland. The histopathological diagnosis for the excised right parathyroid gland was an incompletely resected parathyroid carcinoma. Parathyroid carcinoma in the dog is an infrequent cause of hypercalcemia and primary hyperparathyroidism.

Pretreatment clinical and laboratory findings in dogs with primary hyperparathyroidism: 210 cases (1987–2004)

OBJECTIVE

To evaluate pretreatment clinical and laboratory findings in dogs with naturally occurring primary hyperparathyroidism.

DESIGN

Retrospective study.

ANIMALS

210 dogs with primary hyperparathyroidism and 200 randomly selected, age-matched control dogs that did not have primary hyperparathyroidism.

PROCEDURE

Medical records for dogs with primary hyperparathyroidism were reviewed for signalment; clinical features; and results of clinicopathologic testing, serum parathyroid hormone assays, and diagnostic imaging.

RESULTS

Mean age of the dogs with primary hyperparathyroidism was 11.2 years (range, 6 to 17 years). The most common clinical signs were attributable to urolithiasis or urinary tract infection (ie, straining to urinate, increased frequency of urination, and hematuria). Most dogs (149 [71%]) did not have any observable abnormalities on physical examination. All dogs had hypercalcemia, and most (136 [65%]) had hypophosphatemia. Overall, 200 of the 210 (95%) dogs had BUN and serum creatinine concentrations within or less than the reference range, and serum parathyroid hormone concentration was within reference limits in 135 of 185 (73%) dogs in which it was measured. Urolithiasis was identified in 65 (31 %) dogs, and urinary tract infection was diagnosed in 61 (29%). Mean serum total calcium concentration for the control dogs-was significantly lower than mean concentration for the dogs with primary hyperparathyroidism, but mean BUN and serum creatinine concentrations for the control dogs were both significantly higher than concentrations for the dogs with primary hyperparathyroidism.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that urolithiasis and urinary tract infection may be associated with hypercalcemia in dogs-with primary hyperparathyroidism, but that development of renal insufficiency is uncommon.

Endocrine tumors

Because of the diverse nature of endocrine organs, and their vast range of physiologic functions, endocrine tumors encompass a wide range of origination sites and disease entities. The clinical picture of affected individuals is highly dependent on the tissue of origin, and the presence or absence of functional hormone secretions. Identification, localization, and therapeutic strategies, as well as prognosis can vary greatly. Many endocrine tumors have been described in human as well as veterinary patients. This article focuses on endocrine tumors of dogs and cats. Various tumors affecting the pancreas, thyroid, parathyroid, adrenal and pituitary glands are described, including insulinoma, gastrinoma, glucagonoma, and thyroid carcinoma, as well as parathyroid hormone- and growth hormone-secreting tumors. The syndrome of multiple endocrine neoplasia is also described.