Primary hyperparathyroidism in 29 dogs: diagnosis, treatment, outcome and associated renal failure

Ionized hypercalcemia in 238 cats from a referral hospital population (2009-2019)

BACKGROUND

Ionized calcium concentration ([iCa]) is more sensitive for detecting calcium disturbances than serum total calcium concentration but literature on ionized hypercalcemia in cats is limited. Urolithiasis is a possible adverse consequence of hypercalcemia.

HYPOTHESIS/OBJECTIVES

To describe clinical details of diagnoses associated with ionized hypercalcemia in cats and association with urolithiasis.

ANIMALS

Cats (238) seen between 2009 and 2019 at a referral hospital with [iCa] above the normal reference interval.

METHODS

Observational cross-sectional study. Signalment, serum biochemical and imaging findings were reviewed for cats with ionized hypercalcemia considered to be clinically relevant (>1.41 mmol/L). Data were summarized by cause of hypercalcemia (i.e., diagnosis).

RESULTS

Diagnoses for the 238 cats with [iCa] >1.41 mmol/L included: acute kidney injury (AKI; 13%), malignancy-associated (10.1%), idiopathic hypercalcemia (IHC; 10.1%), chronic kidney disease/renal diet-associated (8.4%), iatrogenic (5.5%), primary hyperparathyroidism (2.1%), vitamin D toxicity (2.1%) and granulomatous disease (1.7%). In 112 cases (47.1%), no cause for ionized hypercalcemia could be determined (n = 95), hypercalcemia was transient (n = 12), or the cat was juvenile (<1 year; n = 5). Urolithiasis was identified in 83.3% of AKI, 72.7% of iatrogenic, 61.1% of CKD/renal diet-associated and 50% of IHC cases that were imaged (<50% for other diagnoses). Diagnoses with a high proportion of concurrent total hypercalcemia included primary hyperparathyroidism (100%), vitamin D toxicity (100%), malignancy-associated (71.4%), granulomatous disease (66.7%) and IHC (65.2%).

CONCLUSIONS AND CLINICAL IMPORTANCE

Ionized hypercalcemia was most commonly associated with kidney diseases, neoplasia or IHC. The proportion of urolithiasis cases varied by diagnosis.

Multidetector-Row CT Findings in Dogs with Different Primary Parathyroid Gland Diseases

Primary hyperparathyroidism in dogs is a possibly life-threatening condition, characterized by the excess of parathyroid hormone (PTH) secretion, which leads to an increase in serum ionized calcium level. The utility of computed tomography (CT) in the detection and characterization of parathyroid diseases in dogs has not been assessed to date. Therefore, the aim of this study was to describe the use of multidetector-row CT (MDCT) for the diagnosis of parathyroid disease in dogs. For this descriptive, single-center study, the database of the San Marco Veterinary Clinic was searched for dogs having a suspicion of parathyroid disease who underwent contrast-enhanced MDCT in the period from 2005 to 2021. Dogs with histopathology of the affected parathyroid gland were subsequently considered for inclusion. A total of 22 parathyroid glands were included: 12 adenomas, 8 adenocarcinomas, and two glands with hyperplasia. Several CT features were evaluated, including parathyroid gland affected, lateralization, shape, size, attenuation, and contrast-enhancement. Although the overlap between the appearance of different diseases exists, contrast-enhanced CT was a useful method for the diagnosis of parathyroid disease in dogs.

Minimally invasive video-assisted parathyroidectomy in dogs: Technique description and feasibility study

OBJECTIVE

To describe a minimally invasive approach to the parathyroid gland for the treatment of primary hyperparathyroidism.

STUDY DESIGN

Surgical technique description and clinical case report.

ANIMALS

Five canine cadavers and 5 client-owned dogs with primary hyperparathyroidism.

METHODS

A surgical technique for minimally invasive video-assisted parathyroidectomy (MIVAP), described for humans, was adapted for dogs. With the dog in dorsal recumbency, a 15 mm incision was made on the midline, 1 finger width caudal to the cricoid cartilage of the larynx. A 5 mm 30° rigid endoscope was inserted into the peritracheal space with the aid of a blunt suction dissector, and fine elevators. The parathyroid was subsequently removed using electrocautery and blunt and sharp dissection. The technique was refined in 5 cadaver dogs to assess feasibility, and was subsequently performed in 5 clinical cases.

RESULTS

A minimally invasive approach to the parathyroid gland was possible and allowed successful removal of a parathyroid mass in 5 dogs without complication. The use of fluid ingress was trialed in 1 cadaver and not found to be helpful. The use of a blunt suction dissector greatly facilitated dissection of the peritracheal space.

CONCLUSION

Minimally invasive video-assisted parathyroidectomy is feasible in dogs and was not associated with complications in 5 clinical cases.

CLINICAL SIGNIFICANCE

Minimally invasive techniques tend to reduce morbidity and are popular with pet owners. This study demonstrates that a minimally invasive technique may be considered for parathyroidectomy in dogs.

Incidence, survival time, and surgical treatment of parathyroid carcinomas in dogs: 100 cases (2010-2019)

OBJECTIVE

To evaluate outcomes of dogs with parathyroid carcinoma (PTC) treated by surgical excision and to describe the incidence of postoperative hypocalcemia, degree of hypocalcemia, duration of hospitalization, duration of calcium supplementation, and survival time.

ANIMALS

100 client-owned dogs with PTC admitted to academic, referral veterinary institutions.

PROCEDURES

In a retrospective multi-institutional study, medical records of dogs undergoing surgical excision of PTC between 2010 to 2019 were reviewed. Signalment, relevant medical history, clinical signs, clinicopathologic testing, imaging, surgical findings, intraoperative complications, histologic examination, and survival time were recorded.

RESULTS

100 dogs with PTC were included, and 96 dogs had clinical or incidental hypercalcemia. Common clinical signs included polyuria (44%), polydipsia (43%), hind limb paresis (22%), lethargy (21%), and hyporexia (20%). Cervical ultrasonography detected a parathyroid nodule in 91 of 91 dogs, with a single nodule in 70.3% (64/91), 2 nodules in 25.3% (23/91), and ≥ 3 nodules in 4 (4/91)% of dogs. Hypercalcemia resolved in 89 of 96 dogs within 7 days after surgery. Thirty-four percent of dogs developed hypocalcemia, on the basis of individual analyzer ranges, within 1 week after surgery. One dog had metastatic PTC to the prescapular lymph node, and 3 dogs were euthanized for refractory postoperative hypocalcemia. Estimated 1-, 2-, and 3-year survival rates were 84%, 65%, and 51% respectively, with a median survival time of 2 years.

CONCLUSIONS AND CLINICAL RELEVANCE

Excision of PTC results in resolution of hypercalcemia and excellent long-term tumor control. Surgical excision of PTC is recommended because of resolution of hypercalcemia and a good long-term prognosis. Future prospective studies and long-term follow-up are needed to further assess primary tumor recurrence, metastasis, and incidence of postoperative hypocalcemia.

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.

Investigation of the relationship between ionised and total calcium in dogs with ionised hypercalcaemia

OBJECTIVES

To investigate the relationship between total and ionised calcium concentrations in dogs with ionised hypercalcaemia and to evaluate how albumin influences this relationship.

METHODS

Initially, a reference interval for ionised and total calcium was established using a large population of healthy adult dogs. Our teaching hospital clinical database was searched to identify adult dogs with ionised hypercalcaemia between 2012 and 2017, a time frame when the same sample handling and analysis protocols were in place as for the healthy reference interval population. The relationship between ionised and total calcium concentrations was then examined in the ionised hypercalcaemia population.

RESULTS

Based on biochemical analysis of 351 healthy adult dogs, a reference interval of 1.18 to 1.53 mmol/L for ionised calcium and 2.24 to 2.85 mmol/L for total calcium was established. Using these reference intervals, 63 dogs with ionised hypercalcaemia were identified, of which 23 did not have total hypercalcaemia. Only seven of the 23 dogs with ionised hypercalcaemia and total calcium below the upper limit of the reference interval had hypoalbuminemia. The majority of dogs with ionised hypercalcemia and normal total calcium had a modest increase in ionised calcium.

CLINICAL SIGNIFICANCE

If relying on total calcium alone, more than one third of dogs with ionised hypercalcaemia will be classified as normocalcaemic and the majority of these dogs had normal serum albumin.

Ultrasonographic size of the canine parathyroid gland may not correlate with histopathology

Accurate ultrasonographic differentiation of normal versus abnormal parathyroid glands is important for clinical workup and presurgical screening in dogs with hypercalcemia. In previous published studies, size has been the only ultrasonographic criterion correlated with histologic diagnoses of abnormal parathyroid glands. In this retrospective, cross-sectional study, the medical records of dogs with ultrasonographic examinations of the parathyroid glands and histologic diagnoses of parathyroid gland hyperplasia, adenoma, and adenocarcinoma were evaluated. Ultrasonographic characteristics were recorded for each gland and compared among histologic diagnosis groups. A total of 49 dogs and 59 parathyroid glands were sampled and assigned to the following groups for analyses: adenoma (n = 24), hyperplastic (n = 20), and adenocarcinoma (n = 15). There were no associations with dog age, sex, weight, breed; or gland laterality, location, ultrasonographic shape, or echogenicity among histologic diagnosis groups (P > .05). Parathyroid gland adenocarcinomas were found to be less likely to have a homogeneous echotexture on ultrasonographic evaluation, with hyperplastic glands being smaller (P = .022) and adenocarcinomas being larger (P = .042). While 3 mm was the optimum cutoff for differentiating hyperplastic and neoplastic parathyroid glands in this sample of dogs, values varied widely within groups and there were overlapping values between groups. Therefore, authors caution against using ultrasonographic size as a sole criterion for differentiating hyperplasia from neoplasia and normal versus abnormal parathyroid glands.

Percutaneous ultrasound-guided ethanol ablation for treatment of primary hyperparathyroidism in a cat

Case summary

A 9-year-old male neutered European Shorthair cat was presented owing to vomiting and mild weight loss. Clinical examination was normal, but biochemistry results showed increased concentrations of total calcium (4.05 mmol/l; reference interval [RI] 2.20-2.90 mmol/l) and ionised calcium (iCa) (2.19 mmol/l; RI 1.12-1.40 mmol/l), as well as hypophosphataemia (2.5 mg/dl; RI 3.1-7.5 mg/dl). Parathyroid hormone (PTH) concentration (>1000 pg/ml) was markedly increased, while parathyroid hormone-related protein concentration (<0.8 pmol/l) was normal. Neck ultrasound showed a large left parathyroid mass (13 × 7 × 6 mm). Under general anaesthesia and with ultrasonographic guidance, a fine-needle aspiration of the mass followed by chemical ablation with 2 ml 96% ethanol was performed. The cat was re-evaluated and iCa concentration measured 24 h, 72 h, 5 days, 4 weeks and 4 months post-ablation. Normocalcaemia was reached within 24 h, remained stable throughout the whole evaluation period and the concentration of PTH normalised 4 months later. Vomiting stopped promptly after chemical ablation and a slight change in voice, as well as a mild prolapse of the nictitating membrane, were the only side effects after the treatment but resolved some weeks later.

Relevance and novel information

To our knowledge, this is the first report of successful chemical ablation of a parathyroid mass in a cat with primary hyperparathyroidism. Chemical ablation might therefore be a possible alternative to parathyroidectomy in cats.

Diagnosis and treatment of confirmed and suspected primary hyperparathyroidism in equids: 17 cases (1999-2016)

BACKGROUND

Primary hyperparathyroidism is uncommon in equids.

OBJECTIVES

To describe the diagnostic findings and efficacy of treatment in equids with primary hyperparathyroidism.

STUDY DESIGN

Retrospective case series describing 16 horses and one mule.

METHODS

Cases were identified by retrospective review of records at Cornell University and via an ACVIM listserv query. Inclusion criteria were an equid with hypercalcemia, normal renal function and high parathyroid hormone (PTH) or histopathological diagnosis of a parathyroid adenoma. Equids with normal PTH and PTH-related protein (PTHrP) in the face of hypercalcemia were included as suspect cases.

RESULTS

The most common presenting complaints were weight loss (12/17) and hypercalcemia (10/17). PTH was above reference range in 12/17 cases. Suspected parathyroid tumours were localised in 12/14 equids imaged using ultrasonography alone (2/3), technetium 99m Tc sestamibi scintigraphy alone (1/1) or both modalities (9/10). Three horses did not have imaging performed. Surgical exploration successfully excised tumours in six of 10 cases. Five were located at the thoracic inlet, and surgery resulted in complete cure. One tumour was excised from the thyroid lobe, and the horse remained hypercalcemic. Four other cases explored surgically, four treated medically and three that were not treated also remained hypercalcemic.

MAIN LIMITATIONS

The small study size prohibited statistical analysis.

CONCLUSIONS

Parathyroid adenomas in equids can be successfully localised with ultrasonography and scintigraphy. Surgical excision appears more likely to be successful for single gland disease at the thoracic inlet.

Perioperative characteristics, histological diagnosis, and outcome in cats undergoing surgical treatment of primary hyperparathyroidism

OBJECTIVE

To report perioperative characteristics, complications, histopathologic diagnosis and outcome in cats undergoing surgical treatment for primary hyperparathyroidism (PHPT).

STUDY DESIGN

Multi-institutional, retrospective case series.

ANIMALS

Thirty-two client-owned cats.

METHODS

Medical records of cats treated with surgical removal of 1 or more parathyroid gland(s) with confirmed histopathologic evaluation were reviewed. Cats were divided into preoperative ionized calcium (iCa) groups corresponding to the 33rd, 67th, and 100th percentiles of the preoperative iCa results of the study population. Follow-up consisted of phone conversation with owners or primary veterinarian.

RESULTS

Ionized calcium was above reference range in all cats (median 1.8 mmol/L [interquartile range, 1.5-1.9]). Abnormal tissue was excised after cervical exploration in all cats. The most common histopathologic diagnoses were parathyroid adenoma in 20 of 32 (62.5%) cats and parathyroid carcinoma in 7 of 32 (21.9%) cats. At discharge, 6 of 32 (18.8%) cats had hypercalcemia, 5 of 32 (15.6%) had hypocalcemia, and 21 of 32 (65.6%) were normocalcemic. Preoperative iCa did not correlate with postoperative iCa. The median follow-up time was 332 days (range, 7-3156). Overall median survival time was 1109 days (95% CI, 856-1332). Survival time was not associated with preoperative iCa group, hypocalcemia at discharge, hypercalcemia at discharge, or diagnosis of carcinoma.

CONCLUSION

In this cohort of cats, parathyroid adenoma was the most common cause of PHPT, and surgical treatment resulted in very good median survival time. Preoperative iCa was not predictive of postoperative hypocalcemia.

CLINICAL SIGNIFICANCE

Surgical parathyroidectomy for treatment of PHPT in cats provides a favorable prognosis.

The Use of Percutaneous Ultrasound-Guided Radiofrequency Heat Ablation for Treatment of Primary Hyperparathyroidism in Eight Dogs: Outcome and Complications

Percutaneous ultrasound-guided radiofrequency heat-ablation (UG-RHA) is a therapeutic option for dogs with primary hyperparathyroidism (PHPTH) but information about its outcome is still controversial. This retrospective study aimed to evaluate the outcome and complications of UG-RHA in dogs with PHPTH. The medical records of dogs with PHPTH submitted to UG-RHA between June 2012 and September 2015 in a French referral center were retrospectively reviewed. Eight cases were included. No sex predisposition was found. The median age at diagnosis was 12 years. The most common clinical sign was polyuria/polydipsia. All of the dogs were hypercalcaemic prior to UG-RHA, and all showed a parathyroid nodule identified upon cervical ultrasound. UG-RHA was uneventful, allowing a successful resolution of hypercalcemia in all dogs (8/8). Six out of eight dogs did not receive vitamin D supplementation either pre- or post-procedure. From these, three dogs developed biochemical hypocalcemia, but only one required therapy. Other short-term complications included Horner's syndrome (1/8) and aspiration bronchopneumonia, which led to cardio-respiratory arrest in one large-breed dog (1/8). Long-term complications were scarce, with no recurrence reported in all of the cases that were assessed in follow-up (4/7). This study demonstrates that UG-RHA has few short or long-term complications, and it is a good therapeutic alternative for dogs with PHPTH.

Parathyroid immunohistochemistry in a 12-year-old mixed-breed dog with parathyroid adenocarcinoma

Summary

A 12-year-old, female, spayed, mixed-breed dog with acute lethargy, anorexia and weakness and markedly elevated total and ionised calcium concentration showed an enlarged left cranial parathyroid gland on ultrasonography of the ventral neck. Despite preoperative therapy with furosemide and calcitonin, there was no decline of plasma ionised calcium concentration. The dog deteriorated rapidly and was euthanased two days after initial presentation. Postmortem histopathology revealed parathyroid tissue with characteristics of malignancy as local and vascular invasion. Immunohistochemistry showed parathyroid hormone positive staining of these cells. Unusual clinical presentation and histopathological characteristics are discussed.

Effect of Prophylactic Calcitriol Administration on Serum Ionized Calcium Concentrations after Parathyroidectomy: 78 Cases (2005-2015)

Background

Prophylactic administration of calcitriol has been suggested to mitigate the risk of hypocalcemia after parathyroidectomy. The effect of calcitriol on postoperative serum ionized calcium concentrations has not been evaluated in dogs after parathyroidectomy.

Hypothesis/Objectives

To determine the effect of prophylactic calcitriol administration on postoperative serum ionized calcium (iCa) concentrations in dogs with primary hyperthyroidism (PHPTH) treated by parathyroidectomy.

Animals

Seventy‐eight dogs with primary hyperparathyroidism treated surgically.

Methods

Multi‐institutional retrospective case study. Medical records from 2005 to 2015 were evaluated. Dogs were included if they had a diagnosis of PHPTH and had surgery to remove parathyroid tissue. Serum iCa concentrations were monitored for a minimum of 2 days postoperatively. Two study groups were evaluated: calcitriol administration and no calcitriol administration.

Results

Serial postoperative iCa concentrations measured at 12‐hour time intervals for 2 days postoperatively were positively associated with preoperative iCa concentrations. This association was evident at each time interval, and the effect of preoperative iCa concentrations on postoperative iCa concentrations decreased as time elapsed (12 hours, P < 0.0001; 24 hours, P < 0.0001; 36 hours, P < 0.04; and 48 hours, P = 0.01). Prophylactic calcitriol administration was not found to be significantly associated with postoperative iCa concentrations or its rate of decrease after parathyroidectomy.

Conclusion and Clinical Importance

We found no protective value in administering calcitriol prophylactically to prevent hypocalcemia in the immediate postoperative period (48 hours) after parathyroidectomy. Preoperative iCa concentrations had a significant positive association with postoperative iCa concentrations throughout the monitoring period.

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.

Canine hypoparathyroidism: case report

Primary hypoparathyroidism is an uncommon endocrinopathy in dogs, resulting from absolute or relative deficiency in the secretion of parathormone (PTH). The dog presented signs of hypocalcemia, including muscular spasms, tetany and cramps, evolving to tonic-clonic seizures and fever. Emergency therapy for hypocalcemia included glucose physiological solution at 0.45% and calcium gluconate administered intravenously. Diagnosis was confirmed by the presence of hypocalcemia, hyperphosphatemia and a decrease in parathormone (PTH).

Diagnosis and treatment of primary hyperparathyroidism in a bobcat (Lynx rufus)

An 18-yr-old male bobcat (Lynx rufus) presented with chronic moderate weight loss and acute onset of anorexia and lethargy. Hypercalcemia and azotemia were present on the serum chemistry panel. Abdominal ultrasound revealed hyperechoic renal cortices, but no evidence of neoplasia. Ionized calcium and 25-hydroxyvitamin D were mildly elevated, intact parathyroid hormone was severely elevated, and parathormone-related protein was undetected, suggesting primary hyperparathyroidism with possible renal dysfunction. Azotemia lessened in severity following diuresis, but hypercalcemia persisted; thus primary hyperparathyroidism was considered the most probable differential diagnosis. A second ultrasound including the cervical region revealed a solitary intraparenchymal left thyroid nodule. The nodule was surgically excised; histopathology confirmed a parathyroid adenoma. Although primary hyperparathyroidism was suspected, diagnosis was not achieved from serum chemistry values alone. This case emphasizes the importance of diagnostic imaging and histopathology in the investigation of persistently abnormal laboratory values.

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.

Primary Hyperparathyroidism in Dogs and Cats

The most common cause of primary hyperparathyroidism in dogs and cats is a solitary adenoma involving an extracapsular parathyroid gland. The prognosis is excellent if the affected parathyroid gland is removed. Nonsurgical methods are discussed, although there are no current data to support any benefit over conventional surgery. The common postoperative complication to consider is hypocalcemia. Hypocalcemia can be successfully managed in these animals if it is anticipated and treated promptly.

Retrospective Evaluation of Three Treatment Methods for Primary Hyperparathyroidism in Dogs

The medical records of 110 dogs treated for primary hyperparathyroidism were reviewed. Dogs were treated via parathyroidectomy (n=47), percutaneous ultrasound-guided ethanol ablation (n=15), or percutaneous ultrasound-guided heat ablation (n=48). Forty-five of 48 (94%) parathyroidectomies resulted in control of hypercalcemia for a median of 561 days. Thirteen of 18 (72%) ethanol ablation procedures resulted in control of hypercalcemia for a median of 540 days. Forty-four of 49 (90%) heat-ablation treatments resulted in control of hypercalcemia for a median of 581 days.