Retrospective Evaluation of Three Treatment Methods for Primary Hyperparathyroidism in Dogs

Serum gastrin concentrations in dogs with primary hyperparathyroidism

BACKGROUND

Hypercalcemia has been associated with hypergastrinemia in humans. Hypergastrinemia could be responsible for gastrointestinal (GI) signs in dogs with primary hyperparathyroidism (PHPT).

HYPOTHESIS/OBJECTIVES

(a) Determine whether hypergastrinemia occurs in dogs with PHPT, (b) assess for potential correlations among ionized calcium (iCa), parathyroid hormone (PTH), and serum gastrin concentrations, and (c) determine whether gastrin concentrations decrease after management of PHPT.

ANIMALS

Phase 1: 151 client-owned dogs at the time of PHPT diagnosis, Phase 2: 24 dogs that underwent treatment for PHPT.

METHODS

Dogs with azotemia, concurrent disease, or those receiving acid suppressants were excluded. Twenty-four treated dogs had baseline and repeat quantification of serum gastrin, PTH, and iCa concentrations 4 weeks after treatment. The effect of treatment on gastrin, iCa, and PTH concentrations was assessed using Wilcoxon signed rank sum tests. Fisher exact testing was used to compare the proportion of dogs with hypergastrinemia in dogs with and without GI signs.

RESULTS

Twenty-seven of 151 PHPT dogs (17.9%) had increased pre-treatment serum gastrin concentrations (median, 45.0 ng/L; interquartile range [IQR], 20.0 ng/L). Gastrin concentrations were not correlated with iCa (P = .92) or PTH (P = .60). Treatment of PHPT decreased PTH (P < .001) and iCa concentrations (P < .001), but not gastrin concentrations (P = .15). The proportion of dogs with hypergastrinemia with and without GI signs did not differ (P = 1.00).

CONCLUSIONS AND CLINICAL IMPORTANCE

Mild increases in serum gastrin concentrations may be seen in dogs with PHPT, but this finding is independent of the presence of GI signs.

Case report: Laryngospasm following ethanol ablation of a parathyroid nodule in a dog with primary hyperparathyroidism

A 12-year-old female spayed dachshund was presented for emergency assessment of respiratory distress, characterized by inspiratory dyspnea with stridor. Percutaneous ultrasound-guided ethanol ablation of a functional parathyroid tumor was performed 72-h earlier for management of primary hyperparathyroidism. The dog was hypocalcemic (ionized calcium 0.7 mmol/L, reference interval: 0.9-1.3 mmol/L) at the time of presentation and had evidence of laryngospasm on a sedated oral exam. The dog was managed conservatively with supplemental oxygen, anxiolysis, and parenteral calcium administration. These interventions were associated with rapid and sustained improvement in clinical signs. The dog did not demonstrate any recurrence of signs afterwards. To the authors' knowledge, this is the first description of laryngospasm following ethanol ablation of a parathyroid nodule in a dog that developed hypocalcemia.

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.

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.

Treatment of primary hyperparathyroidism in a Miniature Horse using chemical ablation of abnormal parathyroid tissue localized by 3-phase computed tomography

A 15‐year‐old Miniature Horse mare with persistently increased plasma calcium (total and ionized) and serum parathyroid hormone concentrations was presented for suspected primary hyperparathyroidism. Ultrasonography of the thyroid region identified an enlarged heterogeneous mass axial to the right thyroid lobe suggestive of an enlarged parathyroid gland, which was further confirmed using sestamibi nuclear scintigraphy and 3‐phase computed tomography. Percutaneous ultrasound‐guided ethanol ablation of the mass, a method not previously described in the horse, was performed under general anesthesia resulting in rapid normalization of plasma ionized calcium and serum parathyroid hormone concentrations. Ablation of abnormal parathyroid gland tissue may be a suitable alternative to surgical resection in certain cases of primary hyperparathyroidism in the horse.

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.

Ultrasound-Guided Radiofrequency Ablation of Chemodectomas in Five Dogs

Chemodectomas are low prevalence tumors with complex clinical management. Many present as an incidental finding however, in other dogs, they produce pericardial effusion and/or compression, leading to the appearance of severe clinical signs. There are currently several approaches: surgery, radiotherapy, stent placement and chemotherapy. This is the first description of percutaneous echo-guided radiofrequency ablation of aortic body tumors. This minimally invasive treatment is based on high frequency alternating electrical currents from an electrode that produces ionic agitation and generates frictional heat, causing coagulation necrosis. Five dogs with an echocardiographic and cytological diagnosis of chemodectoma underwent percutaneous echo-guided radiofrequency ablation. At the time of presentation, all the dogs showed clinical signs, such as ascites and/or collapse. There were no complications either during the procedure or in the following 24 hours. Rapid clinical improvement associated with a reduction in size and change in sonographic appearance of the mass were achieved with no complications. Six months follow-up was carried out in all dogs. A second percutaneous echo-guided RFA was performed eight months after the first procedure in one dog. Based on our experience, radiofrequency ablation seems to be a feasible and safe technique, making it a potential alternative therapeutic approach in the clinical management of aortic body tumors leading to severe clinical compromise.

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.

Primary hyperparathyroidism due to a cystic parathyroid adenoma in a cat

A 15-year-old neutered female domestic shorthair cat was presented for weight loss, polydipsia/polyuria, and lethargy. A large fluctuant mass was palpated in the ventral right cervical region. Biochemistry results were consistent with primary hyperparathyroidism. Parathyroid hormone level in the fluid was higher to that observed in the plasma, consistent with a cystic parathyroid lesion. Right parathyroidectomy and thyroidectomy were performed without complications. Ionized calcium normalized within a few hours. Histopathology yielded a diagnosis of cystic parathyroid adenoma. Follow-up showed complete recovery of clinical signs and normalization of ionized calcium. This case shows an uncommon presentation of feline primary hyperparathyroidism secondary to a cystic parathyroid adenoma and is, to our knowledge, the first case presented with a large palpable mass in which parathyroid hormone concentration was measured. This report highlights the value of selective hormonal analyses of the cystic fluid to confirm the origin of the cystic lesion pre-operatively.

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.

Veterinary Clinics: Tumor Ablation

Over the past decade, interventional oncology techniques have become integrated into the treatment plans of companion animals with cancer on a regular basis. Although procedures such as stenting are performed commonly, other less frequently utilized techniques for locoregional therapy, such as embolization and ablation, are emerging and demonstrating promise. Tumor ablation techniques are categorized into two subgroups: chemical ablation and energy-based ablation. Increased utilization of ablation will allow for the determination of specific indications and evaluation of outcomes for these techniques.

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.

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.

[Diagnostic approach and management of hypercalcaemia in dogs exemplary of primary hyperparathyroidism]

Hypercalcaemia can be caused by many different diseases. This article summarizes the causes, pathophysiologic mechanisms and diagnostic procedures as well as treatment recommendations. The main focus is on hypercalcaemia in primary hyperparathyroidism (PH), complemented by a case report. An elevated total calcium level should generally be investigated and verified by measurement of ionized calcium concentration. The further diagnostic approach depends on the phosphate level. Tumour screening, measurement of parathormone and parathromone-related protein and sonography of parathyroid glands may be necessary. If the calcium-phosphate-product exceeds 60 mg/dl, there is a risk of tissue mineralisation and a rapid treatment of hypercalcaemia is required. For acute therapy, sodium chloride infusion, furosemide and glucocorticoids can be used. Glucocorticoids should only be given after strict indication and after a definite diagnosis. For long-term management, bisphosphates, particularly alendronate, are increasingly used successfully. Causal therapy of PH can be performed by parathyreoidectomy, heat ablation or ethanol ablation. Thereafter, particularly in cases of severe preoperative hypercalcaemia, hypocalcaemia can occur. Treatment is performed using vitamin D₃ (calcitriol), which may also be given preoperatively in cases of severe hypercalcaemia. A concomitant oral calcium supplementation using calcium carbonate as medication of choice is contentious. Due to a potential relapse after successful excision of the affected parathyroid gland in PH, the serum calcium level should be monitored periodically.

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.

Comparison of elastography, contrast-enhanced ultrasonography, and computed tomography for assessment of lesion margin after radiofrequency ablation in livers of healthy dogs

OBJECTIVE To assess by use of various diagnostic imaging modalities acute changes in livers of healthy dogs after radiofrequency ablation (RFA) and determine the capability of each imaging modality to monitor ablation lesion changes.

ANIMALS 6 healthy Beagles.

PROCEDURES 12 ablation lesions were created in the liver of the dogs (2 lesions/dog). Ablation lesions were evaluated by use of conventional ultrasonography, strain elastography, and contrast-enhanced ultrasonography immediately after (time 0), 30 to 60 minutes after, and 3 days after RFA, and by use of CT 30 minutes and 3 days after RFA. Three dogs were euthanized shortly after RFA, and the other 3 dogs were euthanized on day 3. Lesion size measured by each imaging modality was compared with necropsy findings.

RESULTS Immediately after RFA, clear margins were more visible with elastography and contrast-enhanced ultrasonography than with conventional ultrasonography, which had acoustic shadowing. On triphasic contrast CT, the ablation zone, which indicated necrosis and hemorrhage, was not enhanced and could be measured. Marked enhancement of the periablation rim was observed during the venous phase and was identified as granulation tissue. Size of the ablation area measured on enhanced CT images was strongly correlated with actual lesion size.

CONCLUSIONS AND CLINICAL RELEVANCE For dogs of this study, CT was the most reliable method for lesion size determination. Although ultrasonographic imaging measurements underestimated lesion size, all modalities could be used to provide additional real-time guidance for RFA procedures of the liver as well as for other RFA procedures.

Hypercalcaemia in cats: The complexities of calcium regulation and associated clinical challenges

PRACTICAL RELEVANCE

Calcium is essential for many normal physiological processes within the body. Aberrations in calcium homeostasis leading to hypercalcaemia can result in clinical signs such as polyuriav and polydipsia, lethargy and weakness due to depressed excitability of muscle and nervous tissue, and gastrointestinal (GI) signs due to effects on GI smooth muscle. Hypercalcaemia in cats is mostly idiopathic, with chronic kidney disease and neoplasia also being common causes.

CLINICAL CHALLENGES

Hypercalcaemia can be a diagnostic challenge and a good understanding of the regulation of calcium homeostasis can aid in interpreting results of diagnostic tests. Furthermore, the management approach may depend on the underlying cause of hypercalcaemia, and also its severity and chronicity.

AUDIENCE

This review offers a comprehensive discussion of the regulation of calcium homeostasis, with a focus on the normal response to hypercalcaemia. It also discusses the diagnostic approach to, and management of, hypercalcaemia in cats, as well as specific aetiologies. This is relevant to all clinicians working with feline patients.

EVIDENCE BASE

The review draws evidence from peer-reviewed publications and also the author's own clinical experience.

Feline hyperparathyroidism: pathophysiology, diagnosis and treatment of primary and secondary disease

PRACTICAL RELEVANCE

Hyperparathyroidism exists in primary and secondary forms. Primary hyperparathyroidism has typically been considered a disease that uncommonly affects cats, but this condition is more prevalent than previous diagnoses would suggest. Secondary hyperparathyroidism may be caused by either nutritional influences (ie, nutritional secondary hyperparathyroidism) or chronic kidney disease (ie, renal secondary hyperparathyroidism). Tertiary hyperparathyroidism has yet to be documented in veterinary medicine, but it is possible that this condition occurs in some cats following longstanding renal secondary hyperparathyroidism.

CLINICAL CHALLENGES

Diagnosis of this group of calcium metabolic disorders presents a number of challenges for the clinician. For example, clinical signs can be non-specific and, especially in the case of primary hyperparathyroidism, there is often a low index of suspicion for the disease; careful sample handling is required for testing of parathyroid hormone (PTH) and ionized calcium levels; and there is currently no feline-specific assay for PTH, which has implications for test sensitivity and interpretation of results.

AIMS

This article briefly outlines PTH and calcium physiology by way of introduction to a review of PTH measurement and interpretation. Various forms of feline hyperparathyroidism are then described, encompassing diagnosis and treatment options.

Primary hyperparathyroidism caused by a parathyroid carcinoma in a 16-year-old male neutered cat with concurrent chronic kidney disease

A 16-year-old domestic shorthaired cat with chronic kidney disease was presented with a subacute history of weakness and anorexia. Severe hypercalcaemia was identified and attributed to a cervical mass, diagnosed as a parathyroid carcinoma after surgery. Renal function, as evaluated by plasma creatinine, initially worsened during hypercalcaemia but fully returned to previously documented values two months post-operatively.

Persistent Hypercalcemia and Hyperparathyroidism in a Horse

A 27-year-old, American Quarter Horse gelding was evaluated for anorexia, lethargy, a swelling on the right, cranial aspect of the neck, and signs of esophageal obstruction. Serum biochemical analyses revealed hypophosphatemia, total and ionized hypercalcemia, and hemoconcentration. Sonographic examination of the neck revealed a 1.7 cm diameter mass within the right lobe of the thyroid. The serum concentration of intact parathyroid hormone (iPTH) was increased. The right lobe of the thyroid was excised with the horse sedated. The mass within that lobe was determined, by histological examination, to be a parathyroid adenoma. Despite excision of the mass, serial blood analyses revealed persistent hypercalcemia, hypophosphatemia, and increased iPTH. Anorexia and lethargy resolved, and follow-up communication with the owner and referring veterinarian one year later indicated that the horse was clinically stable.

Evaluation of an anal sac adenocarcinoma tumor in a Spitz dog

A 9-year-old emasculated male Spitz with tenesmus and constipation had a subcutaneous mass at the left ventral aspect of the anus with history of polyuria and polydipsia. A complete blood cell count, serum biochemistry panel, and urinalysis (cystocentesis sample) were evaluated. Abnormalities in the serum biochemistry panel included a mildly elevated serum cholesterol concentration (7.28 mmol/L; reference interval, 2.70-5.94 mmol/L), increased serum alkaline phosphatase activity (184 U/L; reference interval, 9-90 U/L), alanine transaminase (122 U/L; reference interval, 5-60 U/L) activity and aspartate aminotransferase (80 U/L; reference interval, 5-55 U/L) activity, severe increased total calcium concentration (16.3 mg/dL; reference interval, 8.2-12.4 mg/dL or 9.3-11.4 mg/dL), and decreased total calcium concentration (3.4 mg/dL, reference interval, 2.5-5.6mg/dL). Furthermore, testing revealed an increased intact parathyroid hormone concentration (38.6 pmol/L; reference interval, 3-17 pmol/L). On cytologic and histopathologic examinations, various types of cells were observed. Most of the cells were oval to polygonal and had elliptical or elongate nuclei and a moderate amount of pale to basophilic cytoplasm. The remaining cells had round to oval nuclei and pale to basophilic cytoplasm. Cells of both types were loosely adhered to each other and were arranged in rosette-like structures. Both neoplastic cell types had fine homogenous chromatin and either a small indistinct nucleolus or no visible nucleolus. Mild anisokaryosis and anisocytosis were observed. Histologically, the mass consists of glandular structures formed by cuboidal cells admixed with bundles of spindle cells. Based on location and histologic features, the final diagnosis was adenocarcinoma of the apocrine gland of the anal sac, which should be included as a cytologic differential diagnosis when spindle cells and typical epithelial cells are observed in masses in the region of the anal sac of dogs.

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.